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Knee osteoarthritis

162 citationsUpdated Oct 2026

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Overview

Knee osteoarthritis is a degenerative condition where recognizing the broader pathophysiological landscape enables clinicians to refine surgical indications and personalize treatments to improve long-term outcomes [1]. While more than 50% of patients referred with mild-to-moderate disease may not require surgery at 7 years [13], arthroscopy may delay the need for arthroplasty in early-stage cases provided proper patient selection is imperative [5]. Arthroscopic indications include mild to moderate arthritis with minimal malalignment and mechanical symptoms consistent with a loose body, meniscus tear, synovitis, or painful osteophytes [5]. Conversely, arthroscopic procedures are contraindicated in advanced arthritis, especially when varus or valgus malalignment is present [5]. Although some studies demonstrate short-term improvement with arthroscopic treatment, most show equivalent outcomes to nonsurgical treatment at mid to long-term follow-up [5], and randomized trials provide strong evidence that arthroscopic surgery offers no added benefit over non-surgical treatment [68].

For patients requiring surgical intervention, total knee replacement combined with a 12-week nonsurgical program is more effective than nonsurgical treatment alone, though it carries a higher risk of serious adverse events [6]. Osteotomy is effective in treating arthritis caused by varus or valgus malalignment and can delay the need for total knee arthroplasty [255]. It is ideal for the young, active patient with isolated medial or lateral compartment disease because it realigns the limb and reduces stresses on the articular cartilage [255]. Medial compartment arthritis in the varus malaligned limb is treated with a valgus-producing high tibial osteotomy [255], while lateral compartment arthritis in the valgus malaligned limb is usually treated with a varus-producing distal femoral osteotomy to avoid an oblique joint line [255]. Biologic therapies, including intra-articular platelet-rich plasma and mesenchymal stromal cells, show promise in early or moderate osteoarthritis, though high-level studies are needed to confirm long-term efficacy [38, 46, 50].

Patients who avoid surgery often experience outcomes that do not improve from baseline and are poorer than those who undergo total knee arthroplasty [160]. Patient preferences for treatment attributes vary within the knee osteoarthritis population [176], and a Malaysian Delphi consensus advocates an algorithmic approach to management [19]. Further studies are necessary to optimize indications and application modalities for conservative treatments, particularly in early osteoarthritis [62, 74]. The MultiKnee trial will contribute to evidence-based personalized treatment recommendations for patients who currently lack an effective treatment option [217]. Detailed management of salvage procedures, such as knee arthrodesis for nonreconstructable total knee arthroplasty failure [262], and specific osteotomy complications are addressed in dedicated sections.

Anatomy & Pathophysiology

Osseous Anatomy

The distal femur exhibits distinct morphological differences between its condyles. The medial femoral condyle is larger and projects farther posteriorly and distally than the lateral femoral condyle [92]. Conversely, the lateral femoral condyle projects farther anteriorly and is wider in the medial-lateral direction [92, 106]. This broader anterior-posterior and medial-lateral dimension of the lateral condyle allows for internal rotation of the distal femur with knee extension [106]. The medial epicondyle serves as the most anterior and distal osseous prominence of the distal femur [92]. It is the origin of the medial collateral ligament (MCL) on the femoral sulcus, located approximately 3.2 cm proximal and 4.8 cm posterior to the articular surface [106]. Proximal to the MCL origin, the adductor tubercle on the medial condyle serves as the insertion site for the adductor magnus muscle [106].

The intercondylar notch is of variable width and serves as the attachment site for the cruciate ligaments [92]. The sulcus terminalis is a small ridge on the lateral femoral condyle just distal to the intercondylar notch that separates the patellofemoral and tibiofemoral articular surfaces [92]. This transverse ridge extends from the oblique facets of the femoral trochlea and is deeper on the lateral condyle than on the medial condyle [106]. Anteriorly, the trochlear groove separates the femoral condyles and constitutes the patellofemoral articulation [92]. The lateral trochlear facet specifically resists lateral subluxation of the patella [106].

The tibial articular surface slopes 7° to 10° in the sagittal plane [92]. Specifically, the posterior slope averages 10.7° in the medial plateau and 7.2° in the lateral plateau [106]. The medial tibial plateau is larger than the lateral plateau and is concave in both frontal and sagittal planes [92]. The lateral tibial plateau is smaller, more circular, concave in the frontal plane, and convex in the sagittal plane [92]. These plateaus are separated by the intercondylar eminence and its medial and lateral spinous processes [92]. The medial compartment features a large surface area with a convex femoral condyle and concave tibial plateau, whereas the lateral compartment has a smaller surface area with a convex femoral condyle and convex lateral plateau in the sagittal plane [106].

The tibial tuberosity is the attachment site for the patellar tendon, typically located in the midline anteriorly but potentially slightly lateral [92]. Gerdy’s tubercle, the insertion site of the iliotibial band, is located 2 to 3 cm lateral to the tibial tubercle on the proximal tibia [92]. The proximal fibula articulates with a facet of the lateral tibial cortex but is not part of the knee articulation [92]. The fibular head is located a mean of 1.5 cm distal to the joint line, with a range of 6 to 32 mm below the joint line [106].

The patella is the largest sesamoid bone in the body, averaging 2.5 cm in thickness [92]. It possesses the thickest articular surface in the body, measuring approximately 5 mm in the midportion and 2 mm on the sides [92]. The patellar articular surface contains a vertical central ridge that separates the broader lateral facet from the medial facet, along with a smaller, more medial odd facet [92, 106]. The odd facet is a small facet on the distal medial patella that articulates in deep flexion of the knee [106]. Patellar morphology is classified by Wiberg types: Type I features medial and lateral facets that are equal in size; Type II, the most common type, features a medial facet that is smaller and one half the size of the lateral facet; and Type III features a medial facet so far medial that the central ridge is barely noticeable [106].

Ligamentous Anatomy

The anterior cruciate ligament (ACL) is composed of 90% type I collagen and 10% type III collagen [92, 106]. Its mean length is 33 mm and mean midsubstance width is 11 mm [92, 106], with some sources citing a length of 30 mm and diameter of 11 mm [93]. The femoral attachment is a semicircular area on the posteromedial aspect of the lateral femoral condyle, measuring 20 mm long and 10 mm wide [92, 106]. This attachment is divided by the bifurcate ridge and bordered by the intercondylar ridge [93]. The tibial attachment is a broad, irregular, oval-shaped area (30 mm long and 10 mm wide) located slightly medial and anterior to the midline, between the medial and lateral tibial spinous processes [92]. It is situated immediately medial to the attachment of the anterior horn of the lateral meniscus and posterior to the tubercle of the anterior horn of the medial meniscus [93]. The ACL consists of two bundles: the anteromedial bundle, which originates proximal to the bifurcate ridge and is tight in flexion, and the posterolateral bundle, which originates distal to the bifurcate ridge and is tight in extension [93, 106]. The posterolateral bundle prevents the pivot-shift phenomenon and stabilizes against anterior translation with 30° of knee flexion, while the anteromedial bundle increases anterior tibial translation at 60° and 90° of knee flexion [106]. The primary function of the ACL is to resist anterior tibial translation in knee flexion, with a secondary role in resisting varus translation in knee extension [93, 111]. The middle geniculate artery provides the primary blood supply, and the posterior articular branch of the posterior tibial nerve provides innervation [106].

The posterior cruciate ligament (PCL) is the largest intra-articular ligament, with an average length of 38 mm and a mean midpoint diameter of 13 mm [106, 114]. Its cross-sectional area is approximately 120% to 150% greater than that of the ACL [114]. The PCL arises from the lateral aspect of the medial femoral condyle and inserts onto the posterior tibia [114]. It is most narrow in its midsubstance, fanning out at both the femoral origin and tibial insertion [114]. The femoral attachment is a broad, semicircular area on the anterolateral aspect of the medial femoral condyle, adjacent to the articular surface, with a mean length of 30 mm and width of 5 mm [106, 114]. In the coronal plane, this attachment is typically between 12 and 4 o'clock in the right knee and between 12 and 8 o'clock in the left knee [114]. The PCL has two distinct bundles defined by their femoral insertion: the anterolateral (AL) bundle and the posteromedial (PM) bundle, separated by a medial bifurcate ridge [106, 114]. The AL bundle is larger, comprising 85% of the PCL's cross-sectional area, and is stronger and stiffer than the PM bundle [106, 114]. The AL bundle is tight in knee flexion, while the PM bundle is tight in knee extension [106]. The tibial insertion is a trapezoidal fossa on the posterior central sulcus, 10 to 15 mm distal to the joint line [106, 114]. The AL bundle occupies the superolateral aspect of the tibial footprint, while the PM bundle occupies the inferomedial aspect [114]. The primary function of the PCL is to resist posterior tibial translation at all degrees of knee flexion, with secondary roles in resisting tibial internal and external rotation beyond 90 degrees of knee flexion and varus translation [93, 111]. The middle geniculate artery is the primary blood supply, and the popliteal artery is near the PCL, with the distance increasing with knee flexion [106]. Innervation is provided by the posterior articular branch of the posterior tibial nerve [106].

At least one meniscofemoral ligament is present in 93% of knees [114]. These ligaments connect the posterior horn of the lateral meniscus to the intercondylar notch and lie anterior (ligament of Humphrey) and posterior (ligament of Wrisberg) to the PCL [114]. They contribute significantly to the PCL footprint and cross-sectional area, with a mean contribution of 17.2% in one cadaver study [114]. Meniscofemoral ligaments are thought to be secondary restraints to posterior translation and act to stabilize the posterior horn of the lateral meniscus [114].

The posterior joint capsule originates at the proximal margin of the posterior femoral condyles and attaches below the tibial plateau [114]. It is continuous medially with the superficial MCL and the posterolateral ligament (POL) [114]. A variably sized defect in the posteromedial joint capsule between the medial head of the gastrocnemius and the direct attachment of the semimembranosus is likely the cause of Baker's cysts [114]. The posterior capsule is strengthened by an expansion from the medial aspect of the popliteus that attaches to the posteromedial joint capsule [114]. The oblique popliteal ligament is a distinct thickening of the capsule arising medially as a confluence of a semimembranosus expansion and an arm of the POL [114]. It is usually 48 mm long and widens from 9.5 mm medially to 16.4 mm at its lateral attachment [114]. The oblique popliteal ligament attaches to both the fabella and the posterior tibia just lateral to the PCL, but did not attach to the lateral femoral condyle in any of the 20 knees dissected by LaPrade et al. [114]. Its primary function is to resist knee hyperextension [93].

The medial collateral ligament (MCL) complex includes the superficial MCL (sMCL) and deep MCL. The sMCL proximal division resists valgus tibial translation, while its distal division resists tibial external rotation in knee extension [93]. The deep MCL resists valgus translation [93]. The posterior oblique ligament resists tibial internal rotation, especially in knee extension [93]. The lateral collateral ligament (LCL) resists varus tibial translation [93]. The popliteus tendon and popliteofibular ligament resist tibial external rotation, especially in knee flexion [93]. The posterolateral complex (PLC) resists posterior translation, external rotation, and varus angulation of the tibia [111]. The medial patellofemoral ligament (PMC) resists valgus stress [111].

Meniscal Anatomy

The menisci are C-shaped, crescent-shaped fibrocartilaginous disks with a triangular cross section [41, 106]. They consist of type I collagen fibers arranged obliquely, radially, and vertically [106]. Their functions include shock absorption, increasing congruency between joint surfaces, enhancing joint stability, and aiding in the distribution of synovial fluid [41]. By providing a concave surface for the convex femoral condyles to articulate with, they prevent the convex condyles from articulating directly with the relatively flat tibial plateaus, which would decrease contact surface area and increase pressure on the articular cartilage [41].

The medial meniscus is firmly attached to the joint capsule along its entire peripheral edge [41]. It attaches more anteriorly and posteriorly than the lateral meniscus [106]. Due to this firm attachment, the medial meniscus has less mobility than the lateral meniscus and is more susceptible to tearing when trapped between the femoral condyle and tibial plateau [41]. The lateral meniscus is circular in shape and covers a larger proportion of the tibial plateau [106]. It is attached to the anterior and posterior capsule, but there is a region posterolaterally where it is not firmly attached [41]. The lateral meniscus is larger than the medial meniscus and carries a greater share of the lateral compartment pressure than the medial meniscus carries for the medial compartment [41]. The anterior attachment of the lateral meniscus is adjacent to the tibial insertion of the ACL [106]. Both menisci are attached to collateral ligaments via coronary ligaments [106].

The vascular supply of the menisci is derived from the geniculate arteries, which penetrate into 20% to 30% of the peripheral medial meniscus and 10% to 25% of the peripheral lateral meniscus [106]. Clinically, the medial meniscus is torn approximately three times more often than the lateral meniscus [83]. Lateral meniscus tears occur more commonly with acute ACL tears [83]. There is an increased rate of osteoarthritis in knees after meniscal tears and meniscectomy, particularly on the lateral side [83]. Traumatic meniscal tears are common in young patients with sports-related injuries, whereas degenerative meniscal tears usually occur in older patients and can have an insidious onset [83].

Meniscal root tears are defined as a radial tear or avulsion of the meniscal root from the tibial plateau [83]. These tears completely disrupt the circumferential fibers of the meniscus [83]. Biomechanically, meniscal root tears result in a loss of hoop stresses and an increase in contact forces, making them functionally equivalent to a total meniscectomy [83]. Lateral root tears are associated with ACL tears, while medial root tears are associated with chondral pathology [83].

Classification

Kellgren-Lawrence (KL): The KL radiological classification is the most commonly used method to grade the severity of knee osteoarthritis in studies [51]. It provides a reliable and accurate tool to assess suitability for patellofemoral knee arthroplasty (PKA) or total knee arthroplasty (TKA) [170]. The original criteria for grade 2 involved "definite osteophytes and possible narrowing of joint space" [242]. Newer versions have used "definite osteophyte, unimpaired joint space" and "minimal osteophytes, possible narrowing, cysts, and sclerosis" [242]. At least two different ways of classifying grade 2 have been reported [242]. Severe knee osteoarthritis is defined as grade 4 [244]. The cutoff grade for defining knee osteoarthritis in the original system involved osteophyte formation and possible joint space narrowing [242].

Ahlbäck: This classification system emphasizes only joint space narrowing and not osteophyte formation for defining knee osteoarthritis [242].

Other Radiographic Systems: The IKDC classification and the Brandt Radiographic Grading Scale for Osteoarthritis have also been used to grade knee osteoarthritis severity [51]. Seven different radiologic classification systems were used in studies of knee osteoarthritis after anterior cruciate ligament injury [242]. Radiographic tibiofemoral osteoarthritis was almost twice as common using OARSI atlas criteria compared with the Kellgren-Lawrence system [204].

Accelerated Knee Osteoarthritis (AKOA): Incident accelerated knee osteoarthritis is defined as having at least one knee with no radiographic osteoarthritis at baseline (KL grade < 2) that developed advanced-stage knee osteoarthritis (KL grade 3 or 4) within 48 months [45]. The index knee in the accelerated group is the first knee that progressed to KL grade 3/4 in 4 years [16]. Common knee osteoarthritis progression is defined as having no radiographic knee osteoarthritis (KL < 2) in both knees at baseline and at least one knee that increased in radiographic scoring within 48 months, excluding those with incident accelerated knee osteoarthritis [45]. The index knee in the typical group is the first knee to increase in KL grade in 4 years [16]. Individuals with no knee osteoarthritis are defined as having no radiographic knee osteoarthritis at baseline in both knees and no change in KL grade in either knee from baseline to 48-month follow-up [45].

Natural History of AKOA: The natural history of incident accelerated knee osteoarthritis is conceptualized as three phases [2]. In the early phase, occurring at least 2 years in advance of radiographic onset, adults may experience greater effusion-synovitis, thicker articular cartilage, diffuse meniscal pathology, and degenerative changes in the cruciate ligaments and extensor mechanism [2]. Accelerated knee osteoarthritis is associated with pre-radiographic degeneration of the extensor mechanism and cruciate ligaments [88]. During this early phase, the joint experiences a greater preradiographic disease burden than peers, which may explain more prodromal symptoms compared to typical knee osteoarthritis [2]. The subsequent 12-month phase is defined by a dramatic rate of worsening in effusion-synovitis, bone marrow lesions, and articular cartilage [2]. Within 12 months before radiographic onset, adults with AKOA report more joint symptoms, frequent use of pain medication, frequent knee swelling, and daily knee pain compared with those who develop typical knee osteoarthritis [2].

Other Considerations: Bilateral knee osteoarthritis is very common, with the majority of sufferers eventually developing radiographic disease in both knees [3]. The highest early knee osteoarthritis prevalence was observed in middle-aged adult females aged 50–59 years [12]. Osteoarthritis is more prevalent among females [237]. The incidence of knee osteoarthritis is significantly different with regions, age, and sex [187]. Patients with end-stage knee osteoarthritis may be classified into four different clinical phenotypes: 'isolated end-stage knee osteoarthritis', 'obesity + hypertension', 'depression + anxiety', and 'rheumatoid arthritis' [66]. In patients with knee osteoarthritis, 74.4% experienced pain consistent with a predominantly nociceptive mechanism [87]. In patients with knee osteoarthritis, 25.6% exhibited either neuropathic pain or central sensitization components [87]. Neuropathic pain and central sensitization in knee osteoarthritis were not associated with radiographic severity [87]. Higher pain at rest was associated with neuropathic pain and central sensitization in knee osteoarthritis [87]. A lack of association between MRI and clinical definitions of early-stage knee osteoarthritis suggests a possible symptom-structure discordance in the early stages of post-traumatic osteoarthritis [15]. Knee biomechanical markers are associated with patient-reported knee function to a greater extent than X-ray grading [8]. Knee biomechanical markers and X-ray grading provide complementary information in the assessment of osteoarthritis patients [8]. A convolutional neural network (CNN) can identify and classify knee osteoarthritis as accurately as a fellowship-trained arthroplasty surgeon [195]. The introduction of AI-based computer-aided assessment systems can increase the agreement rate and overall accuracy for knee osteoarthritis diagnosis among board-certified orthopaedic surgeons [63]. ChatGPT-4o has the potential to rapidly identify and binary classify knee osteoarthritis on radiographs [82]. The DMS model presents a significant advancement in predicting and grading knee osteoarthritis [203].

Clinical Presentation

History and Symptoms

Knee osteoarthritis pain is typically exacerbated by activity and relieved by rest [34]. Patients often describe a deep aching pain accompanied by decreased range of motion and swelling [34]. Pain with weight bearing is aggravated by stairs, inclines, and the transition from sitting to standing [27]. Symptoms tend to worsen when joint space narrowing is underway [54]. In the 12 months preceding radiographic onset of accelerated knee osteoarthritis, patients report more joint symptoms, frequent use of pain medication, frequent knee swelling, and daily knee pain compared with those who develop typical knee osteoarthritis [2]. However, pain remained stable across a one and a half-year period in adults with or at risk for knee osteoarthritis based on quarterly assessments [21]. Clinical symptoms may be caused by meniscal tears [146]. The presence of mixed patellofemoral osteoarthritis might indicate severe clinical knee osteoarthritis [22].

Psychiatric comorbidities are significant. Specific knee OA-related manifestations predict depression and anxiety cross-sectionally, 3 years in the future, and for depression, 7 years in the future [105]. Nearly one-third of patients with symptomatic knee osteoarthritis had clinically significant depressive symptoms, with a higher proportion among women [149]. Knee OA risk factors, joint symptoms, and co-existing multi-site pain are associated with the presence and development of depression [53].

Diagnostic discordance exists between imaging and clinical presentation. A lack of association between MRI and clinical definitions of early-stage knee OA suggests a possible symptom-structure discordance in the early stages of post-traumatic OA disease [15]. Radiographic knee osteoarthritis is an imprecise guide to the likelihood that knee pain or disability will be present [43]. MRI-detected osteoarthritis features are common in asymptomatic individuals and may not necessarily be the source of pain in symptomatic patients [47].

Physical Examination

Inspection: Inspection of the knee can reveal skin abnormalities, evidence of trauma, malalignment, and swelling [163]. Patients with osteoarthritis have an altered gait and increased energy cost [34]. Bowing deformity and instability are seen later in the clinical presentation [27].

Palpation: Palpation of the peripatellar tissue can reveal the presence of effusion and/or synovitis [163]. Physical examination often reveals tenderness along the joint line [34].

Range of Motion: Restricted range of motion and crepitus are common findings [34]. When active and passive ranges of motion differ, the diagnostician must differentiate between pain-related, mechanical, or neuromuscular causes [163].

Stability and Alignment: Varus or valgus alignment should be noted, as well as any gait abnormality [34]. Knee alignment should be assessed in both supine and standing positions, as bearing weight may change the knee’s alignment dynamically [163]. Basic varus and valgus stability testing should be performed at 0° and 30° of flexion [163]. Testing at 30° of flexion isolates the MCL and LCL best, as testing in full extension also engages some secondary stabilizers [163]. Patellar tracking and ligament stability should be assessed [34]. Knee thrust indicates ligament stretch-out on the convex side of the thrust and is seen later in the clinical presentation [27]. Varus thrust involves the knee pushing outward during stance phase of gait, which overloads the medial compartment and accelerates cartilage degeneration in the medial compartment [27]. Valgus thrust involves the knee pushing inward during stance phase of gait, which overloads the lateral compartment and accelerates cartilage degeneration in the lateral compartment [27].

Neuromuscular and Vascular Assessment: Atrophy in muscles crossing the affected joint is often present in chronic disease [34]. Lower extremities should be examined for evidence of muscular atrophy or weakness, with particular attention to hip abductor and quadriceps strength [78]. Distal sensation and vascular perfusion (peripheral pulses) should be assessed in all patients [78].

Red Flags and Referred Pain: Catching or locking, instability in the coronal and/or sagittal plane, or an effusion can signal the presence of a mechanical pathology warranting surgical treatment [78]. The lumbar spine and hips should be examined because pathology in one of these locations can present as referred pain to the knee [78].

Patients with knee osteoarthritis are more likely to display a number of biomechanical characteristics [17]. Knee biomechanical markers are associated with patient-reported knee function to a greater extent than X-ray grading, but both provide complementary information in the assessment of OA patients [8].

Imaging and Diagnostic Criteria

Radiography: Weight-bearing radiographs are the most sensitive for confirming the diagnosis of osteoarthritis [34]. Radiographs are still the standard for initial evaluation of knee osteoarthritis [27]. Plain radiographs are appropriate initial imaging studies for most knee conditions because they allow the assessment of traumatic injury, arthritis, patellofemoral alignment, osteochondral injury, bone neoplasm, and surgical implants [24]. Radiographic studies help confirm the clinical diagnosis of a joint disorder determined using the patient’s history and physical examination [24]. Advanced radiographic imaging studies may help assess overall limb alignment and further delineate intra-articular and extra-articular soft tissues, including cartilage, menisci, ligaments, tendons, muscles, and nerve and vascular structures [24].

Images for initial evaluation should include weight-bearing AP and lateral views, a view of the weight-bearing knee flexed at 45-degree angle imaged posterior to anterior, a sunrise view, extension and flexion lateral views, and a standing full-length AP radiograph [27]. A standing PA view obtained with the patient’s knee in 45° of flexion often is preferred over the standard standing AP view for evaluating knee osteoarthritis [78]. The 45° flexion PA view allows better evaluation of the posterior femoral condyles and earlier detection of subtle joint-space loss than the AP view [78]. Additional radiographs for knee osteoarthritis evaluation should include a lateral view of the affected side and a Merchant or sunrise view of the patellofemoral joint [78]. In the knee, sunrise views and AP views in flexion may demonstrate osteoarthritis not visible on standard AP and lateral views [34].

Radiographic changes in knee osteoarthritis include narrowing of the cartilage space, increased density of the subchondral bone (sclerosis), and osteophytes [34]. Radiography may identify subchondral sclerosis, joint space narrowing, subchondral cysts (variable), osteophytes (variable), and joint subluxation in osteoarthritis [24]. In more severe cases, subchondral cysts (geodes), loose bodies, joint subluxation, deformity, and malalignment may be present [34]. Bony ankylosis is rare but may occur in knee osteoarthritis [34].

Kellgren-Lawrence Classification: The Kellgren-Lawrence (KL) rating grades extent of osteoarthritis based on review of AP knee radiograph using osteophytes and joint space narrowing as primary features [27]. * KL Grade 0: Normal knee features with no osteoarthritis [27]. * KL Grade 1: Osteoarthritis possibly present with a small tibial spine osteophyte and suspected medial joint space narrowing [27]. * KL Grade 2: Minimal osteoarthritis with marginal and tibial spine osteophytes and joint space narrowing less than 50% [27]. * KL Grade 3: Moderate osteoarthritis with significant periarticular and tibial spine osteophytes, articular joint space loss of over 50%, subchondral tibial bone sclerosis, and early bone deformity [27]. * KL Grade 4: Severe osteoarthritis with prominent osteophytes, absent joint space, subchondral bone sclerosis with cysts, and bone deformity with flattening of femoral condyle contours [27].

Knee arthroplasty is recommended when KL Grade 4 findings are present [27].

Advanced Imaging: MRI is grossly overused in the arthritic patient population [27]. If the joint space is significantly narrowed on radiograph, then MRI is not indicated for knee osteoarthritis evaluation [27]. MRI is used when osteonecrosis is suspected in the arthritic knee [27]. MRI may identify the degree of articular cartilage injury (chondrosis, full-thickness cartilage loss), the presence of associated bone marrow edema, and the location of these findings [24]. Three-dimensional CT with remodeling is used for preoperative planning for reconstruction associated with dysplasia, post-trauma planning, and complex total knee arthroplasty planning [27].

Diagnostic Criteria and Epidemiology: The American College of Rheumatology criteria for a clinical diagnosis of knee OA include any three of: 50 years or older, stiffness lasting less than 30 minutes, crepitus felt on passive or active movement of the knee, bony tenderness, bony enlargement, and no warmth to touch [49]. Using a clinical diagnosis is consistent with primary care where x-rays should not be routinely ordered for diagnosis of knee OA [49]. Current guidelines discourage the routine ordering of x rays to confirm a diagnosis of OA [18]. The disease of osteoarthritis is considered to be an active process involving the entire synovial joint with both degenerative and repair processes [18]. Symptomatic knee osteoarthritis affects an estimated 10–12% of the adult population aged 55 years and over [18]. The annual rate of radiographic progression of symptomatic knee osteoarthritis is approximately 3–4% [18]. Bilateral knee osteoarthritis is very common with time, as the majority of sufferers will eventually develop radiographic disease in both knees [3]. Patients with knee osteoarthritis experienced greater progression of osteoarthritis when the contralateral knee was also affected [11]. The highest early knee osteoarthritis prevalence was observed in middle-aged adult females (50–59 years old) [12]. There were clear associations between metabolic factors and radiographic knee osteoarthritis in individuals with knee pain, also in those with normal BMI [25]. In the short term, running is not associated with worsening patient-reported outcomes or radiological signs of knee osteoarthritis and may be protective against generalized knee pain [26]. Moderate- to low-quality evidence suggests no association with OA diagnosis, a positive association with OA diagnosis, and a negative association with knee OA surgery regarding running [48]. Hip and knee OA are common in Europe, though prevalence varies widely across studies and diagnostic approaches [52].

Management Considerations: Artificial intelligence offers a promising solution to improve detection and management of knee osteoarthritis [60]. The introduction of AI-based computer-aided assessment systems can increase the agreement rate and overall accuracy for knee OA diagnosis among board-certified orthopaedic surgeons [63]. These findings highlight the value of a novel clinical assessment strategy for patients with knee OA [61]. This study identified speciality-related variability in some aspects of the management of knee OA [65]. These findings emphasize the importance of weight examination and management in outpatients with knee osteoarthritis for healthcare providers [135]. Symptoms and difficulties experienced by patients with knee OA should be managed by evidence-based information integrating their perceptions and beliefs toward knee OA [138]. Recognizing and addressing the broader pathophysiological landscape of obesity in knee osteoarthritis will enable clinicians to refine surgical indications, personalize treatments, and ultimately improve long-term outcomes [1]. This consensus presents nine recommendations that advocate an algorithmic approach in the management of patients living with knee OA [19]. Experts identified a large number of characteristics for describing patients with knee osteoarthritis [20].

Investigations

Plain radiography: Plain radiographs are the standard initial imaging study for most knee conditions, including traumatic injury, arthritis, patellofemoral alignment, osteochondral injury, bone neoplasm, and surgical implants [24]. The standard protocol includes at least two perpendicular views: AP and lateral [24]. Weight-bearing AP (extension) views assess cartilage loss from the distal femur and tibial plateau, while weight-bearing PA (Rosenberg; flexion) views assess cartilage loss from the posterior femur and tibial plateau [24]. Patellofemoral views evaluate patellofemoral alignment (tilt/subluxation), patellar and trochlear morphology, osteochondral injury, and patellofemoral arthritis [24]. The notch view assesses posterior femoral cartilage, notch width, and osteophytes [24]. For knee arthritis evaluation, standard images include weight-bearing AP and lateral views, a weight-bearing knee flexed at 45-degree angle imaged posterior to anterior, a sunrise view (Merchant view), extension and flexion lateral views, and a standing full-length AP radiograph [27].

The Kellgren-Lawrence (KL) rating grades the extent of OA based on the AP knee radiograph [27]. Primary features include osteophytes (periarticular and tibial spine), joint space narrowing, subchondral sclerosis with or without subchondral cysts, and altered shape of periarticular bones [27]. KL Grade 0 indicates normal knee features with no OA [27]. KL Grade 1 indicates OA possibly present [27]. KL Grade 2 indicates OA present with minimal severity [27]. KL Grade 3 indicates OA present with moderate severity [27]. KL Grade 4 indicates OA present with severe severity [27]. Knee arthroplasty is recommended when Grade 4 findings are present [27].

Supine AP knee radiographs do not adequately estimate the joint space width needed to estimate the degree of osteoarthritis progression [129]. Plain frontal radiographs may not accurately display the actual joint space due to different cartilage wear patterns, meniscal integrity, or variances in tibial slopes [129]. A 45° standing flexion view was introduced by Rosenberg et al. to better evaluate joint space [129]. A fixed flexion view (FFV) technique has been introduced with improved reproducibility and good evaluation of the joint space [129]. The Lyon Schuss view (LSV) uses the same posture as the FFV but requires fluoroscopic adjustment of the irradiation angle relative to the medial tibial plateau, providing more accurate measurement of actual joint space width [129]. The LSV has higher radiation exposure dose and more complex, time-consuming positioning compared to the FFV [129]. Goniometer readings of long limb alignment or measured on an FFV correlate well with the angle measured on long limb radiographs, providing an alternative imaging source if long limb radiographs are not available [129]. One in 3 patients considered to have mild to moderate knee OA on extension AP radiography is upgraded to severe knee OA (KL grade 4) on flexion PA radiography [35].

Radiographic findings including joint space narrowing were significantly associated with the long-term risk of TKA in persons with knee osteoarthritis [254]. A low radiological severity of osteoarthritis was not associated with pain 12 months postoperatively after total knee replacement [205]. Moderate osteoarthritis with a joint space of at least 2 mm on AP radiographs was not a predictor for poor outcome after total knee arthroplasty [270]. The incidence of knee radiographic osteoarthritis in a Chinese suburban area was high [90]. Radiographic signs of osteoarthritis are significant at 8 to 16 years' follow-up after knee arthroscopic partial meniscectomy, but clinical symptoms of knee arthritis are not significant [10]. Obesity, female sex, and preexisting early-stage OA are features associated with poor self-reported and radiographic outcome fifteen to twenty-two years after meniscectomy [32]. ChatGPT-4o has the potential to rapidly identify and binary classify knee OA on radiographs [82].

MRI: MRI is the most useful study for differentiating osteonecrosis from other conditions such as osteochondritis dissecans, transient osteoporosis, bone bruises, or occult fractures [31]. A serpentine lesion within a well-demarcated border is a specific finding on MRI for osteonecrosis [31]. If the joint space is significantly narrowed on radiograph, then MRI is not indicated [27]. MRI is used when osteonecrosis is suspected [27]. There is evidence in some MRI protocols that MRI is a relatively valid, sensitive, specific, accurate, and reliable clinical tool for identifying articular cartilage degeneration [214]. However, MRI contributes less than expected to the understanding of pain and function in knee OA and possibly offers little opportunity to develop structure-modifying treatments in knee OA that could influence the patient's pain and function [198]. Among symptomatic clinically diagnosed OA knees, cartilage lesions observed in the first MRI examinations were not found to be associated with the occurrence of joint surgery within a 5-year period [14].

The presence of mixed patellofemoral osteoarthritis might be an indicator of severe clinical knee OA [22]. Meniscal extrusion is the strongest predictor of OA progression, highlighting the importance of MRI in identifying early changes and guiding personalised management [253]. MRI detected bone marrow lesions, synovitis and effusion were all significantly associated with the long term risk of TKA in persons with knee osteoarthritis [254]. Higher echo intensity on ultrasonography is a feature of early cartilage degeneration in mild knee OA [257]. The MRI radiomics analysis represented promising performance in noninvasive and preoperative KOA diagnosis, especially when considering all available planes of all three compartments of knee joints [233]. An MRI radiomics framework integrating cartilage and subchondral bone features effectively predicts KOA incidence and progression, enhances individualized risk stratification, and facilitates timely clinical decisions [265].

In patients with moderate knee osteoarthritis treated within a standardized SVF-based arthroscopic pathway, adding microfracture was associated with superior 24-month pain and WOMAC improvement and more favourable MRI-based cartilage morphology compared with SVF without microfracture [245]. Micro-fragmented adipose tissue (mFAT) associated with arthroscopic debridement improves functional outcome and MRI appearance in the treatment of knee OA in an arthroscopic setting [260]. In a population-based cohort of predominantly pre-radiographic knee OA, statins did not affect MRI incidence/progression of cartilage damage, BML, osteophytes or effusion [267]. In patients with KOA, the diagnostic value of single radiographic or MRI parameter in assessing the functional integrity of the ACL are equivalent [269]. Stage of joint destruction, assessed on either radiographs or low-field MRI (0.2T), does not preclude a symptoms relief following a clinically relevant weight loss in elderly obese female patients with knee osteoarthritis [215]. The study demonstrates previously undescribed subchondral vascular marks on axial MRI scans of the tibia and their inverse correlation with the presence and severity of early knee osteoarthritis [263]. Gut and joint microbiome alterations in patients with knee osteoarthritis are associated with perturbations of metabolic and inflammatory pathways, imaging findings, OA-related pain, and patient-reported outcome measure performance [264].

CT: CT provides a three-dimensional study performed with ionizing radiation that provides enhanced bone detail [24]. Three-dimensional CT reconstructions may help with preoperative planning for complex intra-articular fractures, multiplanar osteotomy for limb malalignment, and reconstitution of bone loss in joint arthroplasty [24]. Three-dimensional CT with remodeling is used for preoperative planning for reconstruction associated with dysplasia, post-trauma planning, and complex total knee arthroplasty (TKA) planning [27].

Bone scan: Nuclear medicine provides a nonspecific study that does not define the etiology of an abnormality but rather the presence of an abnormality that may correlate with a clinical concern [24]. Increased radionuclide activity in bone may be a normal postoperative finding for up to 6 to 12 months after a fracture repair or arthroplasty [24]. Technetium-99 (Tc-99) is a radionuclide that may help identify infection, neoplasia, occult fracture, bone healing, active phases of heterotopic ossification, implant loosening, or failure of osseointegration [24]. Gallium-67 (Ga-67) is a radionuclide that may help differentiate between aseptic and septic prosthetic loosening; 24 to 72 hours are needed for a complete study [24].

Other Considerations: Physical examination along with radiographic or advanced imaging findings must be used concomitantly to determine the source of each patient’s symptoms and to determine appropriate surgical intervention when nonsurgical measures have failed [4]. Assessment of the joint must combine physical examination along with radiographic (including full-length alignment views) and MRI findings [59]. Patient assessment of knee pain includes a physical examination and diagnostic radiographic modalities [27]. Recognizing and addressing the broader pathophysiological landscape of knee OA will enable clinicians to refine surgical indications, personalize treatments, and ultimately improve long-term outcomes in patients with knee OA [1].

Treatment

Non-Operative

A stepwise approach with graduated interventional treatment is recommended as pain and functional disability progress in knee osteoarthritis [79]. Patient education programs, exercise (including supervised, unsupervised, and aquatic modalities), and self-management programs are strong recommendations for management [79]. Pharmacologic management includes strong recommendations for topical NSAIDs, oral NSAIDs, and oral acetaminophen [79]. Oral narcotics, including tramadol, are not recommended [79]. Moderate recommendations include canes, brace treatment, neuromuscular training combined with traditional exercise, and sustained weight loss [79]. Intra-articular corticosteroids are a moderate recommendation for short-term relief [79]. Arthroscopic partial meniscectomy is a moderate recommendation for meniscal tears in patients with concomitant mild to moderate osteoarthritis [79]. Hyaluronic acid intra-articular injections, lateral wedge insoles, and arthroscopy with lavage and/or débridement are not recommended [79].

Supplements including turmeric, ginger extract, glucosamine, chondroitin, and vitamin D may be helpful [79], although oral supplementation with glucosamine and/or chondroitin sulfate has no benefit for symptomatic osteoarthritis of the knee [55]. Manual therapy in addition to an exercise program, massage in addition to usual care, FDA-approved laser treatment, acupuncture, transcutaneous electrical nerve stimulation, percutaneous electrical nerve stimulation, electromagnetic field therapy, and extracorporeal shockwave therapy may be used or may improve pain and function [79]. Platelet-rich plasma may reduce pain and improve function [79]. Denervation therapy may reduce pain and improve function [79]. High tibial osteotomy may improve pain and function in properly indicated patients with unicompartmental knee osteoarthritis [79]. Dry needling has unclear utility and efficacy [79]. Free-floating interpositional devices, such as unispacers, are not recommended [79].

Maintenance of a healthy body weight is effective for decreasing symptom severity and slowing progression [178]. Obesity increases the likelihood of symptomatic knee osteoarthritis disease as much as threefold [178]. Forces at the knee are magnified to three to seven times the actual body weight [178]. Patients with a body mass index above 25 kg/m2 should strive to lose at least 5% of their current body weight [178]. Intra-articular corticosteroid injections are effective for symptomatic management [55]. More than 50% of patients referred with mild-moderate knee OA may not need surgery at 7 years [13]. Low-intensity long-duration ultrasound may be used as a conservative non-pharmaceutical and non-invasive treatment option [23]. Hyaluronic acid injections provided statistically significant but not clinically important improvements in knee pain and function compared with oral NSAIDs, along with a lower overall risk of adverse events [28]. Cooled radiofrequency ablation is not likely to replace current treatments for OA but may have a role in delaying the need for knee replacement in some patients or may benefit patients who are not candidates for knee replacement [76]. Radiofrequency treatment is an efficacious and safe treatment for relieving knee pain and improving knee function [133]. Ultrasound-guided dextrose 25% hypertonic prolotherapy and intra-articular normal saline injection are both effective and well tolerated [141]. A six-week physiotherapist-led exercise and education intervention resulted in sustained significant improvements in pain severity and interference in patients with hip or knee osteoarthritis awaiting arthroplasty [199].

Physical therapy programs should be comprehensive and functional, focusing on core and lower body function, and include muscle strengthening, stretching/flexibility/range of motion, and aerobic exercise [202]. Home exercise programs for knee osteoarthritis should recommend strengthening exercises 2-3 times per week, range of motion exercises daily, and moderate intensity aerobic activity with a long-term goal of 150 minutes per week [202]. Modalities for pain management in physical therapy should be used conservatively, taking no more than 25% of the time of each clinic visit [202]. The 10 mg dose of triamcinolone acetonide is non-inferior to the 40 mg dose in improving pain in patients with symptomatic knee osteoarthritis [207]. Crespine Gel Plus may be considered a non-surgical option providing year-long symptomatic relief [169]. One-shot hyaluronic acid injection is an effective and safe treatment for advanced knee OA, providing significant improvements in pain, stiffness, and function over six months [139]. Amniotic suspension allograft injection is an effective treatment for the nonoperative management of symptomatic knee osteoarthritis [191]. Micro-fragmented aspirated tissue injection therapy is effective and improves pain and functional outcomes in symptomatic knee osteoarthritis [158]. Kneipp hydrotherapy is a noninvasive, non-interventional therapeutic option with few side effects for the concomitant treatment of osteoarthritis of the hip or knee [221].

Operative

Indications: The primary indication for TKA is to relieve pain caused by severe arthritis, with or without significant deformity [39]. Other sources of knee and leg pain, including radicular pain, referred hip pain, peripheral vascular disease, meniscal pathology, and bursitis, must be systematically excluded before TKA [39]. Radiographic findings must correlate with a clear clinical impression of knee arthritis before surgery is considered [39]. Conservative treatment measures should be exhausted before surgery is considered for TKA [39]. Patients who do not have complete cartilage space loss before surgery tend to be less satisfied with their clinical result after TKA [39]. TKA generally is indicated in older patients with more sedentary lifestyles due to finite expected survival adversely affected by activity level [39]. TKA is clearly indicated in younger patients who have a significant functional impairment from OA or other pathologic causes such as systemic arthritis or osteonecrosis with subchondral collapse [39]. Severe pain from chondrocalcinosis and pseudogout in an elderly patient is an occasional indication for arthroplasty in the absence of complete cartilage space loss [39]. Severe patellofemoral arthritis in an elderly patient may justify TKA because the expected outcome of arthroplasty is better than that of patellectomy or patellofemoral replacement [39]. Deformity can become the principal indication for arthroplasty when the progression of deformity begins to threaten the expected outcome of an anticipated arthroplasty [39]. As a flexion contracture progresses beyond 20 degrees, gait is significantly hampered and difficulty with regaining extension may warrant surgical intervention [39]. As varus or valgus laxity becomes severe, a constrained condylar type of prosthesis may become necessary to prevent subsequent coronal plane instability [39]. Intervening before severe laxity is present allows the use of a prosthesis that lacks coronal plane constraint and has a more favorable expected survivorship [39].

Absolute contraindications to TKA include recent or current knee sepsis, a remote source of ongoing infection, extensor mechanism discontinuity or severe dysfunction, recurvatum deformity secondary to neuromuscular weakness, and the presence of a painless, well-functioning knee arthrodesis [39]. Relative contraindications to TKA include medical conditions compromising anesthesia tolerance, immunodeficiency, significant atherosclerotic disease of the operative leg, skin conditions such as psoriasis within the operative field, venous stasis disease with recurrent cellulitis, neuropathic arthropathy, superobesity (BMI ≥ 45), recurrent urinary tract infections, and a history of infections in the proximity of the knee [39]. A severely osteoarthritic ipsilateral hip joint should be considered for ar

Surgical Approach / Technique: Total knee replacement plus a 12-week nonsurgical treatment program was more effective than nonsurgical treatment alone but was associated with more serious adverse events [6]. In the absence of mechanical symptoms, arthroscopic débridement has not been shown to be an effective treatment strategy for knee osteoarthritis [55]. The evidence does not support the effectiveness of arthroscopic knee surgery compared to conservative treatments in knee OA [58]. Arthroscopic surgery provides no added benefit over non-surgical treatment for knee OA [68]. Arthroscopic débridement for the management of mild to moderate knee OA is effective at short-term follow-up in patients who have exhausted conservative care [171]. Performing arthroscopy for the treatment of early-stage osteoarthritis of the knee may help delay the need for knee arthroplasty, but proper patient selection is imperative [5]. The literature lacks well-designed studies to evaluate the efficacy of arthroscopic procedures for knee OA, with most demonstrating equivalent outcomes to nonsurgical treatment at mid to long-term follow-up [5]. Arthroscopic lavage and débridement indications are limited to specific mechanical symptoms caused by loose bone, cartilage flaps or particles, meniscal tears, or synovial impingement [5]. The irrigation during arthroscopic lavage dilutes the joint fluid, which reduces the concentration of degradative enzymes [5]. The removal of loose cartilage, meniscus, and/or synovium during arthroscopy reduces mechanical symptoms and removes a source of irritation to the synovial tissue [5]. The potential for thermal damage when using a laser or radiofrequency probe for chondroplasty has resulted in decreased use of these techniques [5]. The goal of abrasion arthroplasty is the formation of a blood clot, which undergoes metaplasia to become fibrocartilage, a process estimated to take 8 weeks [5]. Fibrocartilage formed after abrasion arthroplasty is primarily composed of type I collagen as opposed to the type II collagen of normal hyaline cartilage [5]. The goal of subchondral drilling or microfracture is to create bleeding bone, which produces a blood clot and subsequent fibrocartilage [5]. Some studies have demonstrated by 2 years post-operatively that the fibrocartilage cap from microfracture is significantly degraded or no longer present [5]. Arthroscopic knee débridement may provide relief from mechanical symptoms in carefully selected osteoarthritis patients, but should not be offered as a first-line treatment in lieu of nonsurgical measures [59]. Arthroscopy can be beneficial for patients with OA and mechanical symptoms recalcitrant to conservative care, but this should not be the first-line intervention [59]. Arthroscopic treatment is indicated for débridement, chondroplasty, loose body removal, microfracture, and partial meniscectomy [59]. Treatment for focal cartilage lesions depends upon the lesion size, lesion location, and the status of the underlying subchondral bone [59]. Surgical options for treatment of focal cartilage injury include bone marrow stimulation techniques, osteochondral autograft or allograft transplantation, autologous cell-based therapy, and allograft therapies [59]. Allograft meniscal transplantation can provide significant symptomatic relief and improvements in quality of life for symptomatic meniscal deficiency, although radiographic OA may still progress [59]. Correction of ligamentous instability and limb malalignment is paramount to success of cartilage restoration procedures and meniscal transplantation [59]. For isolated medial compartment degeneration, surgical options include medial opening wedge high tibial osteotomy, lateral closing wedge HTO, or unicompartmental knee arthroplasty [59]. Lateral compartment OA can be treated with lateral closing wedge distal femoral osteotomy, medial opening wedge DFO, medial closing wedge HTO, or UKA [59]. In selected patients, nonarthroplasty surgical procedures such as realignment osteotomy can help to alleviate symptoms and delay the need for joint arthroplasty surgery [55]. The best indication for osteotomy in post-traumatic knee osteoarthritis is moderate unicompartmental knee arthritis [71]. In case of failure of osteotomy, correction of the initial deformity facilitates the total knee replacement procedure [71]. Temporary relief with unloader bracing treatment could predict pain relief after valgus-producing high-tibial osteotomy [33]. A matched cohort study showed that an unloader brace group had fewer injections and longer time to TKA compared to an unbraced group [33].

Implant Selection: As varus or valgus laxity becomes severe, a constrained condylar type of prosthesis may become necessary to prevent subsequent coronal plane instability [39]. Intervening before severe laxity is present allows the use of a prosthesis that lacks coronal plane constraint and has a more favorable expected survivorship [39].

Other Considerations: Platelet-rich plasma demonstrated significantly improved pain and function for patients with knee osteoarthritis compared with placebo at a minimum 6-month follow-up [30]. Patients undergoing treatment for knee OA with PRP can be expected to experience improved clinical outcomes when compared with hyaluronic acid [64]. PRP, particularly when combined with HA, provides superior long-term pain relief and functional improvement in knee OA compared to other intra-articular injectables [67]. The administration of three or five injections of platelet-rich plasma is safe, substantially more effective than single injections, and leads to remarkable clinical improvement in patients with grade I-III knee osteoarthritis [156]. PRP and plasma were not superior to placebo for pain and function improvement in knee osteoarthritis over 24 weeks [143]. PRP injections are considered appropriate in patients aged ≤80 years with knee KL 0–III OA grade after failed conservative non-injective or injective treatments [239]. PRP injections are not considered appropriate as first treatment nor in KL IV OA grade [239]. French-speaking experts consider intra-articular PRP injections an effective treatment especially in early or moderate knee osteoarthritis [38]. Available clinical practice guidelines favor IA-CS and IA-HA for different needs, while PRP currently has insufficient evidence to make a conclusive recommendation for or against its use [154]. The authors of a systematic review and meta-analysis are not able to make recommendations for clinical practice regarding PRP for knee osteoarthritis [165]. Bone marrow aspirate concentrate (BMAC) injection is effective in improving pain and patient-reported outcomes in patients with knee OA at short-to midterm follow-up [70]. BMAC injections demonstrated effectiveness in providing pain relief and functional improvement for patients with knee OA [155]. Both PRP and BMC were effective in improving patient-reported outcomes in patients with mild to moderate knee OA for at least 12 months, with neither treatment providing a superior clinical benefit [142]. Intra-articular mesenchymal stromal cells demonstrated efficacy and safety supporting their implementation as a treatment option for symptomatic knee OA [50]. The symptomatic treatment effect of stromal vascular fraction (SVF) injections was found to be dose dependent, and the efficacy, safety, and ease of use support its use as a treatment option for symptomatic knee osteoarthritis [115]. Intra-articular knee injection of SVF is safe and effective to ameliorate clinical and functional scores in patients with early knee osteoarthritis for 6 months [120]. Some degree of efficacy has been shown for cartilage regeneration in knee OA using autologous adipose-derived stem cells or stromal vascular fractions, although the evidence remains limited [69]. The clinical outcomes of mesenchymal stem cell implantation for knee OA are encouraging [152]. The efficacy of mesenchymal stem cell treatment regarding clinical outcomes and cartilage regeneration in knee osteoarthritis remains unclear due to large heterogeneity in cell sources, preparation methods, and delivery techniques [144]. Biologic therapies for knee osteoarthritis appear to have evidence justifying their use, though more high-level, larger human studies utilizing standardized protocols are needed [46].

Complications

Accelerated Disease Progression

The natural history of accelerated knee osteoarthritis (AKOA) includes a phase starting at least 2 years before radiographic onset characterized by greater effusion-synovitis, thicker articular cartilage, diffuse meniscal pathology, and degenerative changes in cruciate ligaments and the extensor mechanism [2]. In the 12-month phase preceding radiographic onset of AKOA, there is a dramatic rate of worsening in effusion-synovitis, bone marrow lesions, and articular cartilage [2]. Adults with AKOA report more joint symptoms, frequent use of pain medication, frequent knee swelling, and daily knee pain within 12 months before radiographic onset compared with those who develop typical knee osteoarthritis [2]. The symptoms of knee OA patients tend to be worse when joint space narrowing is underway [54]. In a community-based cohort, more than 1 in 7 women with incident knee osteoarthritis had accelerated knee osteoarthritis [72].

Surgical Complications: Arthroscopy and Preservation

Some studies have demonstrated that arthroscopic treatment of the knee shows equivalent outcomes to nonsurgical treatment at mid to long-term follow-up [5]. By 2 years post-operatively, the fibrocartilage cap formed after subchondral drilling or microfracture is significantly degraded or no longer present in some studies [5]. Patella baja (scar contracture of tendon) is the most common complication of the open-wedge high tibial osteotomy technique [228]. Collapse of the open wedge, nonunion, and bone harvest site pain are complications associated with the open-wedge high tibial osteotomy technique [228]. Peroneal nerve palsy due to aberrant retractor placement is a complication of the closed-wedge high tibial osteotomy technique [228]. The rate of conversion from high tibial osteotomy to total knee arthroplasty is 13% at 6 years [228]. Conversion from high tibial osteotomy to total knee arthroplasty requires longer operative time and more frequent use of revision implants [228]. Nonunion and loss of wedge correction are complications of distal femoral osteotomy, with loss of correction most common in patients with osteoporotic bone [228]. Residual patellofemoral maltracking is a complication of distal femoral osteotomy that may require patellofemoral realignment [228].

Surgical Complications: Arthroplasty

Total knee replacement plus a 12-week nonsurgical treatment program was associated with more serious adverse events than nonsurgical treatment alone [6]. Infection is the number one reason for revision total knee arthroplasty and the number one reason for revision within 2 years of index primary TKA [250]. Aseptic mechanical implant loosening is the second most common reason for revision total knee arthroplasty [250]. Early aseptic loosening can result from failure of osteointegration into cementless implants or debonding of the implant from PMMA in cemented fixation [250]. Late aseptic loosening can result from PMMA fatigue, bone resorption away from cement, or osteolysis with bone resorption from cement [250]. Malposition and/or malalignment of implants typically presents with knee stiffness and activity-related pain [250]. Instability in total knee arthroplasty results in abnormal excessive limb subluxation or angulation with weight-bearing stress [250]. Early wear presentation of polyethylene debris manifests as a warm knee and effusion due to reactive synovitis [250]. Late wear presentation of polyethylene debris manifests as osteolysis with bone resorption and retroprosthetic bone resorption creating excess bone strain and pain [250]. Patellofemoral complications occurred in 4% of patients with patellar resurfacing compared with 12% of patients in whom the patella was unresurfaced in a large retrospective study [256]. Significant residual anterior knee pain was the most common complication in the unresurfaced patella group [256]. In a 5-year prospective, randomized study, 25% of patients with unresurfaced patellas complained of anterior knee pain, whereas only 5% of patients with patellar resurfacing complained of anterior knee pain [256]. Secondary resurfacing of the patella for residual anterior knee pain after TKA has a higher rate of complications, including patellar fracture and postoperative stiffness, compared to primary resurfacing [256]. Complications of resurfaced patellae account for most of the reoperations after TKA in many series [256]. An increasing rise in infection and other complications has been noted as obesity classification increased from severe to super-obese [39]. UKA versus TKA in patients with BMI >40 shows increased clinical failure at 2 years for UKA (29%) compared to TKA (3%) [228]. Long-term survivorship of unicompartmental knee arthroplasty is not comparable with total knee arthroplasty when measured by revision rates [228]. In a 27-year Finnish registry study, unicompartmental knee arthroplasty survivorship was lower than TKA survivorship [249]. Revision of a painful TKA without an identified specific cause of pain is likely to have a poor outcome [250]. Referred pain from the hip is the most common missed diagnosis in the evaluation of a painful TKA [250].

Post-Traumatic and Secondary Complications

Infection, heterotopic ossification, posttraumatic osteoarthritis, and arthrofibrosis are common complications associated with the management of knee dislocation [201]. The reported rate of infection following knee dislocation management is 12.5% [201]. The reported incidence of heterotopic ossification following knee dislocation management is approximately 25% [201]. PCL reconstruction is one independent risk factor for the development of heterotopic ossification after knee dislocation [201]. The incidence of posttraumatic arthritis in a retrospective long-term follow-up study of 44 multiligament reconstructions was 23% [201]. A mean of 38% of patients (range, 5% to 71%) require surgical management of arthrofibrosis after knee dislocation [201]. Recurrent instability after knee dislocation reconstruction has a mean incidence of approximately 40% [201]. The incidence of pain following knee dislocation injuries has been reported from 25% to 68% [201]. Patients reported improved knee function and minimal-to-moderate pain at a minimum 10-year follow-up after knee dislocation surgery, with age at surgery being a predictor of OA development [29].

Diagnostic and Reporting Complications

Harms-related data are poorly reported within RCTs cited as supporting evidence for the American Academy of Orthopaedic Surgeons management for hip and knee OA Clinical Practice Guideline [37].

Recovery

Light activity (weeks): The provided evidence does not specify a typical week range for light activities such as desk work, driving, or light ADLs.

Full activity (months): The provided evidence does not specify a month range for the return to manual work, sport, or full ROM/strength.

Complete recovery / outcome plateau (months): The provided evidence does not specify a month range for when pain, strength, and final functional outcomes stabilise.

Rehabilitation protocol: The provided evidence does not detail specific PT phasing, immobilisation duration, weight-bearing/ROM progression, or sling/brace removal timing.

Functional milestones: Clinical measures of knee function were most predictive of subsequent OA development following an extended period of rehabilitation early after ACL injury [276].

Other Considerations: The natural history of accelerated knee osteoarthritis (AKOA) is conceptualized as three phases, starting at least 2 years in advance of radiographic onset with greater effusion-synovitis, thicker articular cartilage, diffuse meniscal pathology, and degenerative changes in the cruciate ligaments and extensor mechanism [2]. During the early phase of AKOA (at least 2 years before radiographic onset), adults experience a greater preradiographic disease burden than peers, which may explain more prodromal symptoms compared to those who develop typical knee osteoarthritis [2]. Joint trauma, often characterized by a destabilizing meniscal tear, may be a triggering event in a joint with an impaired ability to heal, ultimately leading to joint failure in AKOA [2]. In a 3-year longitudinal study of elderly community residents in Korea, the yearly incidence and progression of knee OA was higher than those previously reported in Western populations [89].

Obesity, female sex, and preexisting early-stage OA are features associated with poor self-reported and radiographic outcome 15 to 22 years after meniscectomy [32]. Women who developed radiographically defined knee OA had significantly greater odds of having baseline endogenous early follicular phase estradiol concentrations in the lowest tertile (OR 1.86, 95% CI 1.01-3.44) [273]. At 10-year follow-up after ACL reconstruction, radiological signs of OA were present in 53.5% of subjects, with meniscectomy prior to or at the time of ACL reconstruction and chondral lesions at the time of ACL reconstruction identified as risk factors [272]. Age at surgery was a predictor of OA development in patients undergoing knee dislocation surgery [29].

Ultrasound may be used as a conservative non-pharmaceutical and non-invasive treatment option for patients with knee osteoarthritis [23]. For short-term follow-up (≤1 year), intra-articular PRP injection is more effective in terms of pain relief and function improvement in the treatment of KOA patients than HA and placebo, and there is no difference in the risk of an adverse event between PRP and HA or placebo [57]. At a minimum 6-month follow-up, PRP demonstrated significantly improved pain and function for patients with knee osteoarthritis compared with placebo [30]. These findings emphasize the sustained efficacy of PRP, particularly when combined with HA, in providing superior long-term pain relief and functional improvement in knee OA compared to other intra-articular injectables [67]. PRP did not improve pain at 24 weeks of follow-up in patients with mild-to-moderate knee osteoarthritis compared with exercise alone [226]. A short cycle of intra-articular treatment with polynucleotides in fixed combination with high molecular weight hyaluronic acid is more effective in improving knee function and pain in knee OA patients than HA alone at 2-year follow-up [277]. RFA is effective in improving both knee pain and function in patients with OA, at least in the short term (6 months) [211]. MSC implantation provided encouraging outcomes with acceptable duration of symptom relief at midterm follow-up in patients with early knee OA [77].

In 2 multicenter cohorts of patients with knee osteoarthritis, substantial numbers of patients had premature total knee replacement as well as patients for whom total knee replacement was potentially appropriate but had not been performed >2 years after it had become potentially appropriate [7]. Long-term studies show better clinical outcomes and less degenerative osteoarthritis changes following meniscal repair than following partial meniscectomy [209]. The survival rate of closed-wedge high tibial osteotomy (CWHTO) for severe medial knee OA was 90.1% at 10 years, 83.8% at 15 years, and 75.9% at 20 and 35 years [216]. Patients and clinicians can expect an average procedure survival of 12.5 years and a maximum of 21 years for medial opening wedge high tibial osteotomies, with effective pain relief influenced by cartilage treatment and preoperative pain score [275]. Articular cartilage debridement for large focal chondral defects in the setting of mild to moderate osteoarthritis results in significant improvements in physical function and knee-specific PROs at minimum one-year follow-up [81]. The association of definite knee osteoarthritis in medial patellofemoral ligament reconstruction with or without lateral release was small in the long-term follow-up [210]. Patients with hip OA progressed faster and to a greater extent to arthroplasty than patients with knee OA [274].

Key Evidence

• [L5] Recognizing and addressing this broader pathophysiological landscape will enable clinicians to refine surgical indications, personalize treatments, and ultimately improve long-term outcomes in patients with knee OA. [1] (10.1002/arj.70051)
• [L5] [2] (10.1186/s12891-020-03367-2)
• [L2] Bilateral knee osteoarthritis is very common with time, as the majority of sufferers will eventually develop radiographic disease in both knees. [3] (10.1186/1471-2474-13-153)
• [L1] In patients with knee osteoarthritis, total knee replacement plus a 12-week nonsurgical treatment program was more effective than nonsurgical treatment alone but was associated with more serious adverse events. [6] (10.2106/jbjs.16.00208)
• [L3] In 2 multicenter cohorts of patients with knee osteoarthritis, we observed substantial numbers of patients who had premature total knee replacement as well as of patients for whom total knee replacement was potentially appropriate but had not been performed >2 years after it had become potentially appropriate. [7] (10.2106/jbjs.19.00432)
• [L2] Knee biomechanical markers are associated with patient-reported knee function to a greater extent than X-ray grading, but both provide complementary information in the assessment of OA patients. [8] (10.1186/s12891-022-05845-1)
• [L1] It also demonstrated a good safety profile in symptomatic knee osteoarthritis. [9] (10.1186/s12891-026-09625-z)
• [L1] Radiographic signs of osteoarthritis are significant at 8 to 16 years' follow-up after knee arthroscopic partial meniscectomy, but clinical symptoms of knee arthritis are not significant. [10] (10.1016/j.arthro.2010.08.016)
• [L3] Patients with knee osteoarthritis experienced greater progression of osteoarthritis when the contralateral knee was also affected. [11] (10.1186/s12891-024-07292-6)
• [L4] The highest early knee osteoarthritis prevalence was observed in middle-aged adult females (50–59 years old). [12] (10.1007/s00167-019-05614-z)
• [L3] More than 50% of patients referred with mild-moderate knee OA may not need surgery at 7 years. [13] (10.1016/j.arth.2020.01.086)
• [L3] Among symptomatic clinically diagnosed OA knees, cartilage lesions observed in the first MRI examinations were not found to be associated with the occurrence of joint surgery within a 5-year period. [14] (10.1186/s12891-024-07225-3)
• [L3] A lack of association between MRI and clinical definitions of early-stage knee OA suggests a possible symptom-structure discordance in the early stages of post-traumatic OA disease. [15] (10.1177/23259671261455852)
• [L2] [16] (10.1186/s12891-020-03338-7)
• [L1] Patients with knee osteoarthritis are more likely to display a number of biomechanical characteristics. [17] (10.1186/s12891-018-2202-8)
• [Paper] [18] (10.1186/1471-2474-5-4)
• [L5] This consensus presents nine recommendations that advocate an algorithmic approach in the management of patients living with knee OA. [19] (10.1186/s12891-021-04381-8)
• [L5] Experts identified a large number of characteristics for describing patients with knee osteoarthritis. [20] (10.1186/1471-2474-14-369)
• [L2] Pain remained stable across a one and a half-year period in adults with or at risk for knee osteoarthritis, based on quarterly assessments. [21] (10.1186/s12891-021-04284-8)
• [L2] The presence of mixed patellofemoral osteoarthritis might be an indicator of severe clinical knee osteoarthritis. [22] (10.1186/s12891-017-1486-4)
• [L1] The clinical findings suggest that ultrasound may be used as a conservative non-pharmaceutical and non-invasive treatment option for patients with knee osteoarthritis. [23] (10.1186/s13018-018-0965-0)
• [L4] There were clear associations between metabolic factors and radiographic knee osteoarthritis in individuals with knee pain, also in those with normal BMI. [25] (10.1186/s12891-022-05881-x)
• [L4] In the short term, running is not associated with worsening patient-reported outcomes or radiological signs of knee osteoarthritis and may be protective against generalized knee pain. [26] (10.1177/23259671231152900)
• [L1] Comparing short-term outcomes of HA injections with oral NSAIDs for treatment of knee OA, HA injections provided statistically significant but not clinically important improvements in knee pain and function, along with a lower overall risk of AEs. [28] (10.1177/2325967119897909)
• [L3] Patients reported improved knee function and minimal-to-moderate pain, with age at surgery being a predictor of OA development. [29] (10.1007/s00167-017-4443-8)
• [L1] At a minimum 6-month follow-up, PRP demonstrated significantly improved pain and function for patients with knee osteoarthritis compared with placebo. [30] (10.1016/j.arthro.2024.01.037)
• [L3] Obesity, female sex, and preexisting early-stage OA are features associated with poor self-reported and radiographic outcome. [32] (10.1002/art.20489)
• [L3] One in 3 patients considered to have mild to moderate knee OA on extension AP radiography is upgraded to severe knee OA (KL grade 4) on flexion PA radiography. [35] (10.1177/2325967117706692)
• [L2] Long-term clinical trials are required to determine if these biological advantages translate into a delay in the progression of knee osteoarthritis. [36] (10.1002/ksa.12796)
• [L4] Harms-related data are poorly reported within RCTs cited as supporting evidence for the American Academy of Orthopaedic Surgeons management for hip and knee OA Clinical Practice Guideline. [37] (10.1016/j.arth.2022.06.004)
• [L1] The 25 recommendations should standardize and facilitate the use of intra-articular PRP injections, which are considered by experts as an effective treatment especially in early or moderate knee osteoarthritis. [38] (10.1007/s00167-020-06102-5)
• [L1] Radiographic knee osteoarthritis is likewise an imprecise guide to the likelihood that knee pain or disability will be present. [43] (10.1186/1471-2474-9-116)
• [L3] [45] (10.1186/s12891-016-1158-9)
• [L2] Despite these limitations, there appears to be evidence justifying their use for knee osteoarthritis management, though more high-level, larger human studies utilizing standardized protocols are needed. [46] (10.1016/j.arth.2018.12.001)
• [L1] These findings suggest that MRI-detected osteoarthritis features are common in asymptomatic individuals and may not necessarily be the source of pain in symptomatic patients. [47] (10.1136/bjsports-2018-099257)
• [L1] Moderate- to low-quality evidence suggests no association with OA diagnosis, a positive association with OA diagnosis, and a negative association with knee OA surgery. [48] (10.1177/0363546516657531)
• [L2] [49] (10.1186/1471-2474-13-246)
• [L1] The efficacy and safety demonstrated in this placebo-controlled trial support its implementation as a treatment option for symptomatic knee OA. [50] (10.1177/0363546519899923)
• [L1] [51] (10.3390/cells10061365)
• [L1] Hip and knee OA are common in Europe, though prevalence varies widely across studies and diagnostic approaches. [52] (10.1186/s12891-026-09493-7)
• [L2] Knee OA risk factors and joint symptoms, along with co-existing multi-site pain are associated with the presence and development of depression. [53] (10.1186/s12891-020-03875-1)
• [L2] The symptoms of knee OA patients tend to be worse when joint space narrowing is underway. [54] (10.1186/1471-2474-11-269)
• [L1] For short-term follow-up (≤1 year), intra-articular PRP injection is more effective in terms of pain relief and function improvement in the treatment of KOA patients than HA and placebo, and there is no difference in the risk of an adverse event between PRP and HA or placebo. [57] (10.1186/s13018-019-1363-y)
• [L1] The evidence does not support the effectiveness of arthroscopic knee surgery compared to conservative treatments in knee OA. [58] (10.1186/s12891-024-07813-3)
• [L4] Artificial intelligence offers a promising solution to improve detection and management of knee osteoarthritis. [60] (10.1186/s42836-022-00118-7)
• [L4] These findings highlight the value of a novel clinical assessment strategy for patients with knee OA. [61] (10.2519/jospt.2016.6311)
• [L4] Further studies are needed to increase the limited evidence on non-surgical treatments and their combination, to optimize indications, application modalities, and results with particular focus on early OA. [62] (10.1007/s00167-016-4089-y)
• [L2] The introduction of AI-based computer-aided assessment systems can increase the agreement rate and overall accuracy for knee OA diagnosis among board-certified orthopaedic surgeons. [63] (10.1007/s00167-022-07220-y)
• [L1] Patients undergoing treatment for knee OA with PRP can be expected to experience improved clinical outcomes when compared with HA. [64] (10.1177/0363546520909397)
• [L4] This study identified speciality-related variability in some aspects of the management of knee OA. [65] (10.1186/1471-2474-12-72)
• [L4] Patients with end-stage knee osteoarthritis may be classified into four different clinical phenotypes: 'isolated end-stage knee osteoarthritis', 'obesity + hypertension', 'depression + anxiety', and 'rheumatoid arthritis', which may help guide individualized patient care and treatment strategies. [66] (10.1186/s12891-024-07394-1)
• [L1] These findings emphasize the sustained efficacy of PRP, particularly when combined with HA, in providing superior long-term pain relief and functional improvement in knee OA compared to other intra-articular injectables, highlighting its potential as a preferred treatment modality. [67] (10.1186/s13018-025-05574-w)
• [L1] These findings provide strong evidence that arthroscopic surgery provides no added benefit over non-surgical treatment for knee OA. [68] (10.1016/j.arthro.2009.04.054)
• [L1] Some degree of efficacy has been shown for cartilage regeneration in knee OA, although the evidence remains limited. [69] (10.1177/03635465211053893)
• [L4] The BMAC injection is effective in improving pain and patient-reported outcomes in patients with knee OA at short-to midterm follow-up. [70] (10.1177/03635465211018837)
• [L4] The best indication is moderate unicompartmental knee arthritis, and in case of failure, correction of the initial deformity facilitates the total knee replacement procedure. [71] (10.1016/j.otsr.2010.06.012)
• [L2] In a community-based cohort, more than 1 in 7 women with incident knee osteoarthritis had accelerated knee osteoarthritis. [72] (10.1186/s12891-020-3073-3)
• [L4] Further studies are necessary to increase the limited medical evidence on conservative treatments, optimizing results, application modalities, indications, and focusing on early OA. [74] (10.1007/s00167-011-1713-8)
• [L5] CRFA is not likely to replace the current treatments for OA, but it may have a role in delaying the need for knee replacement in some patients or may benefit patients who are not candidates for knee replacement. [76] (10.2106/jbjs.20.01209)
• [L4] MSC implantation provided encouraging outcomes with acceptable duration of symptom relief at midterm follow-up in patients with early knee OA. [77] (10.1177/2325967120969189)
• [L3] Articular cartilage debridement for large focal chondral defects in the setting of mild to moderate osteoarthritis results in significant improvements in physical function and knee-specific PROs at minimum one-year follow-up. [81] (10.1177/2325967125s00234)
• [L3] ChatGPT-4o has the potential to rapidly identify and binary classify knee OA on radiographs. [82] (10.1002/ksa.12639)
• [L4] [87] (10.1186/s12891-026-09747-4)
• [L2] [88] (10.1186/s12891-019-2685-y)
• [L2] In this 3-year longitudinal study, the yearly incidence and progression of knee OA was higher than those previously reported in Western populations. [89] (10.1186/s12891-018-1999-5)
• [L2] The incidence of knee radiographic osteoarthritis in a Chinese suburban area was high. [90] (10.1186/s13018-021-02577-1)
• [L2] Specific knee OA-related manifestations predict depression and anxiety cross-sectionally, 3 years in the future, and for depression, 7 years in the future. [105] (10.1186/s12891-020-03496-8)
• [L1] The symptomatic treatment effect was found to be dose dependent, and the efficacy of SVF injections, in combination with its safety and ease of use, supports its use as a treatment option for symptomatic knee osteoarthritis. [115] (10.1177/2325967120s00127)
• [L4] Intra-articular knee injection of SVF is safe and effective to ameliorate the clinical and functional scores in patients with early knee osteoarthritis for 6 months. [120] (10.1186/s13018-022-03196-0)
• [L1] This meta-analysis showed that RF is an efficacious and safe treatment for relieving knee pain and improving knee function in patients with knee OA. [133] (10.1186/s13018-021-02906-4)
• [L4] These findings emphasize the importance of weight examination and management in outpatients with knee osteoarthritis for healthcare providers. [135] (10.1186/s12891-025-08432-2)
• [L5] Symptoms and difficulties experienced by patients with knee OA should be managed by evidence-based information integrating their perceptions and beliefs toward knee OA. [138] (10.1186/s12891-021-04641-7)
• [L4] The results support the use of IA HA as an effective and safe treatment for advanced knee OA, providing significant improvements in pain, stiffness, and function over six months. [139] (10.1186/s12891-025-08875-7)
• [L1] Both treatments are effective and well tolerated for knee osteoarthritis. [141] (10.1186/s12891-025-08580-5)
• [L2] Both PRP and BMC were effective in improving patient-reported outcomes in patients with mild to moderate knee OA for at least 12 months; neither treatment provided a superior clinical benefit. [142] (10.1177/2325967119900958)
• [L1] PRP and plasma were not superior to placebo for pain and function improvement in knee osteoarthritis over 24 weeks. [143] (10.1186/s12891-021-04706-7)
• [L5] The efficacy of mesenchymal stem cell treatment regarding clinical outcomes and cartilage regeneration in knee osteoarthritis remains unclear due to large heterogeneity in cell sources, preparation methods, and delivery techniques; future studies with consistent protocols are required to validate the theoretical potential of stem cell treatments. [144] (10.1016/j.arthro.2020.11.017)
• [L3] These results suggest that clinical symptoms in patients with osteoarthritis of the knee may be caused by meniscal tears. [146] (10.1007/s00167-014-2939-z)
• [L4] Nearly one-third of patients with symptomatic knee osteoarthritis had clinically significant depressive symptoms, with a higher proportion among women. [149] (10.1186/s12891-025-09453-7)
• [L4] The clinical outcomes of MSC implantation for knee OA are encouraging. [152] (10.1177/0363546515588317)
• [L1] Available clinical practice guidelines provide recommendations on injectables for knee OA treatment, favoring IA-CS and IA-HA for different needs, while PRP currently has insufficient evidence to make a conclusive recommendation for or against its use. [154] (10.1177/23259671211030272)
• [L1] BMAC injections demonstrated effectiveness in providing pain relief and functional improvement for patients with knee OA. [155] (10.1177/23259671241296555)
• [L2] The administration of three or five injections of platelet-rich plasma is safe, substantially more effective than single injections, and leads to remarkable clinical improvement by significantly reducing knee pain, improving joint stiffness, and enhancing physical function in patients with grade I-III knee osteoarthritis. [156] (10.1186/s13018-024-04736-6)
• [L4] Micro-fragmented aspirated tissue injection therapy for the treatment of symptomatic knee osteoarthritis is effective and improves pain and functional outcomes. [158] (10.1016/j.arthro.2024.03.002)
• [L3] Although a high proportion of patients with knee OA have avoided surgery at 5 years, their outcomes show no improvement from baseline and are poorer than those who have undergone TKA. [160] (10.1016/j.arth.2020.04.087)
• [L2] Therefore, the authors are not able to make recommendations for clinical practice regarding PRP for knee osteoarthritis. [165] (10.1177/03635465211062243)
• [L3] Crespine Gel Plus may be considered a non-surgical option providing year-long symptomatic relief for patients with knee OA. [169] (10.1186/s12891-026-09588-1)
• [L2] The KOGS classification provides a reliable and accurate tool to assess suitability of an individual patient for undergoing PKA or TKA. [170] (10.1016/j.arth.2018.11.011)
• [L4] Arthroscopic debridement for the management of mild to moderate knee OA is effective at short-term follow-up in patients who have exhausted conservative care. [171] (10.1016/j.arthro.2024.03.016)
• [L4] Patient preferences for various treatment attributes varied among patients in a knee osteoarthritis population. [176] (10.2106/jbjs.20.00132)
• [L5] The incidence of knee osteoarthritis is significantly different with regions, age and sex. [187] (10.1186/s12891-024-07191-w)
• [L1] The evidence presented in this Level I Randomized Controlled Trial suggests that ASA injection is an effective treatment for the nonoperative management of symptomatic knee OA. [191] (10.1055/s-0039-1696672)
• [L4] A CNN can identify and classify knee OA as accurately as a fellowship-trained arthroplasty surgeon. [195] (10.1016/j.arth.2020.04.059)
• [L4] MRI contributes less than expected to the understanding of pain and function in knee OA and possibly offers little opportunity to develop structure-modifying treatments in knee OA that could influence the patient's pain and function. [198] (10.1007/s00167-013-2434-y)
• [L1] [199] (10.1186/s12891-016-1088-6)
• [L1] [202] (10.1016/j.joca.2017.12.008)
• [L5] The DMS model presents a significant advancement in predicting and grading knee OA, holding substantial clinical importance. [203] (10.1186/s13018-024-05352-0)
• [L3] Radiographic tibiofemoral OA was almost twice as common using OARSI atlas criteria compared with the K/L system. [204] (10.1007/s00167-014-3205-0)
• [L3] A low radiological severity of osteoarthritis was not associated with pain 12 months postoperatively. [205] (10.1302/0301-620x.96b11.33726)
• [L1] The 10 mg of TA is non-inferior to 40 mg TA in improving pain in patients with symptomatic knee OA. [207] (10.1186/s12891-023-06191-6)
• [L5] Long-term studies show better clinical outcomes and less degenerative osteoarthritis changes following meniscal repair than following partial meniscectomy. [209] (10.3390/life12040603)
• [L4] The association of definite knee osteoarthritis in medial patellofemoral ligament reconstruction with or without lateral release was small in the long-term follow-up. [210] (10.1177/0363546507306161)
• [L1] RFA is effective in improving both knee pain and function in patients with OA, at least in the short term (6 months). [211] (10.1016/j.arthro.2022.01.048)
• [L4] Therefore, based on the data from this study, orthopaedic surgeons may consider recommending MAT as a salvage procedure even in knees affected by early to moderate OA, while advising patients that the need for combined interventions could potentially reduce graft survival. [212] (10.1177/03635465241253849)
• [L1] There is evidence in some MRI protocols that MRI is a relatively valid, sensitive, specific, accurate, and reliable clinical tool for identifying articular cartilage degeneration. [214] (10.1177/0363546511407612)
• [L2] Stage of joint destruction, assessed on either radiographs or low-field MRI (0.2T), does not preclude a symptoms relief following a clinically relevant weight loss in elderly obese female patients with knee osteoarthritis. [215] (10.1186/1471-2474-12-56)
• [L4] The survival rate of CWHTO for severe medial knee OA was 90.1% at 10 years, 83.8% at 15 years, and 75.9% at 20 and 35 years. [216] (10.1177/23259671211046964)
• [L2] Findings from this trial will contribute to evidence-based personalized treatment recommendations for a large proportion of OA patients who currently lack an effective treatment option. [217] (10.1186/s12891-021-04924-z)
• [L2] The results will contribute to establishing hydrotherapy as a noninvasive, non-interventional, reasonably priced, therapeutic option with few side effects, in the concomitant treatment of osteoarthritis of the hip or knee. [221] (10.1186/1471-2474-10-104)
• [L1] PRP did not improve pain at 24 weeks of follow-up in patients with mild-to-moderate knee osteoarthritis compared with exercise alone. [226] (10.1097/corr.0000000000002993)
• [L3] The MRI radiomics analysis represented promising performance in noninvasive and preoperative KOA diagnosis, especially when considering all available planes of all three compartments of knee joints. [233] (10.1186/s13018-023-03837-y)
• [L4] Osteoarthritis is more prevalent among females. [237] (10.1186/s13018-025-05805-0)
• [L1] PRP injections are considered appropriate in patients aged ≤80 years with knee KL 0–III OA grade after failed conservative non-injective or injective treatments, while they are not considered appropriate as first treatment nor in KL IV OA grade. [239] (10.1002/ksa.12320)
• [L1] [242] (10.1177/0363546509338827)
• [L2] [244] (10.1186/1471-2474-14-266)
• [L1] In patients with moderate knee osteoarthritis treated within a standardized SVF‐based arthroscopic pathway, adding microfracture was associated with superior 24‐month pain and WOMAC improvement and more favourable MRI‐based cartilage morphology compared with SVF without microfracture. [245] (10.1002/ksa.70377)
• [L2] Meniscal extrusion is the strongest predictor of OA progression, highlighting the importance of MRI in identifying early changes and guiding personalised management. [253] (10.1002/ksa.70016)
• [L2] Radiographic findings including joint space narrowing and MRI detected bone marrow lesions, synovitis and effusion were all significantly associated with the long term risk of TKA in persons with knee osteoarthritis. [254] (10.1186/s12891-017-1871-z)
• [L3] Higher echo intensity is a feature of early cartilage degeneration in mild knee OA. [257] (10.1007/s00167-023-07440-w)
• [L1] mFAT improves functional outcome and MRI appearance when used in association with AD, therefore supporting its use in the treatment of knee OA in an arthroscopic setting. [260] (10.1007/s00167-022-07101-4)
• [L4] The study demonstrates previously undescribed subchondral vascular marks on axial MRI scans of the tibia and their inverse correlation with the presence and severity of early knee osteoarthritis, offering new insight into the possible vascular aetiology of osteoarthritis. [263] (10.1186/s13018-018-0991-y)
• [L2] These alterations are associated with perturbations of metabolic and inflammatory pathways, imaging findings, OA-related pain, and patient-reported outcome measure performance. [264] (10.1016/j.arthro.2024.05.010)
• [L2] The MRI radiomics framework integrating cartilage and subchondral bone features effectively predicts KOA incidence and progression, enhances individualized risk stratification, and facilitates timely clinical decisions. [265] (10.1186/s12891-025-09234-2)
• [L3] In this population-based cohort of predominantly pre-radiographic knee OA, statins did not affect MRI incidence/progression of cartilage damage, BML, osteophytes or effusion. [267] (10.1186/s12891-022-05900-x)
• [L3] In patients with KOA, the diagnostic value of single radiographic or MRI parameter in assessing the functional integrity of the ACL are equivalent. [269] (10.1186/s42836-024-00262-2)
• [L3] Moderate osteoarthritis with a joint space of at least 2 mm on AP radiographs was not a predictor for poor outcome. [270] (10.1007/s00402-021-03785-4)
• [L2] At 10-year follow-up, radiological signs of OA were present in 53.5% of subjects, with meniscectomy prior to or at the time of ACL reconstruction and chondral lesions at the time of ACL reconstruction identified as risk factors. [272] (10.1007/s00167-012-2234-9)
• [L2] Women who developed radiographically defined knee OA had significantly greater odds of having baseline endogenous early follicular phase estradiol concentrations in the lowest tertile (OR 1.86, 95% CI 1.01-3.44). [273] (10.1002/art.22005)
• [L3] Patients with hip OA progressed faster and to a greater extent to arthroplasty than patients with knee OA. [274] (10.1302/0301-620x.104b7.bjj-2021-1766.r1)
• [L4] Patients and clinicians can expect an average procedure survival of 12.5 years and a maximum of 21 years, with effective pain relief influenced by cartilage treatment and preoperative pain score. [275] (10.1136/jisakos-2017-000169)
• [L2] Clinical measures of knee function were most predictive of subsequent OA development following an extended period of rehabilitation early after ACL injury. [276] (10.1177/2325967118810775)
• [L2] The outcomes of the 2-year study confirmed that a short cycle of intra-articular treatment with polynucleotides in fixed combination with high molecular weight hyaluronic acid is more effective in improving knee function and pain in knee OA patients than HA alone. [277] (10.1186/s12891-021-04648-0)

See Also

• Total Knee Replacement
• High tibial osteotomy
• Distal femoral osteotomy
• Anterior cruciate ligament injury
• Partial meniscectomy
• Meniscal tear
• ACL reconstruction
• Meniscal repair

References

[1] Reframing Obesity in Knee Osteoarthritis: A Call for a Transdisciplinary Approach Beyond Biomechanics. Arthroscopy. 2026. DOI: 10.1002/arj.70051

[2] Risk factors and the natural history of accelerated knee osteoarthritis: a narrative review. BMC Musculoskeletal Disorders. 2020. DOI: 10.1186/s12891-020-03367-2

[3] Is knee osteoarthritis a symmetrical disease? Analysis of a 12 year prospective cohort study. BMC Musculoskeletal Disorders. 2012. DOI: 10.1186/1471-2474-13-153

[4] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Arthroscopy and Preservation, Knee Reconstruction > Introduction.

[5] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Knee > I. Arthroscopic Management of the Arthritic Knee.

[6] Total Knee Replacement Plus Nonsurgical Treatment Was Better Than Nonsurgical Treatment Alone for Knee Osteoarthritis. Journal of Bone and Joint Surgery. 2016. DOI: 10.2106/jbjs.16.00208

[7] Examining Timeliness of Total Knee Replacement Among Patients with Knee Osteoarthritis in the U.S.. Journal of Bone and Joint Surgery. 2020. DOI: 10.2106/jbjs.19.00432

[8] Biomechanical markers associations with pain, symptoms, and disability compared to radiographic severity in knee osteoarthritis patients: a secondary analysis from a cluster randomized controlled trial. BMC Musculoskeletal Disorders. 2022. DOI: 10.1186/s12891-022-05845-1

[9] Efficacy and safety of a combination of platelet-rich plasma with non-crosslinked hyaluronic acid versus a crosslinked hyaluronic acid, in single-injection for knee osteoarthritis. Randomized, controlled, multicenter, non-inferiority trial. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09625-z

[10] Does Arthroscopic Partial Meniscectomy Result in Knee Osteoarthritis? A Systematic Review With a Minimum of 8 Years' Follow‐up. Arthroscopy. 2010. DOI: 10.1016/j.arthro.2010.08.016

[11] Contralateral knee osteoarthritis is a risk factor for ipsilateral knee osteoarthritis progressing: a case control study. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07292-6

[12] Early knee osteoarthritis prevalence is highest among middle-aged adult females with obesity based on new set of diagnostic criteria from a large sample cohort study in the Japanese general population. Knee Surgery, Sports Traumatology, Arthroscopy. 2019. DOI: 10.1007/s00167-019-05614-z

[13] The Outcomes of Nonoperative Management of Patients With Hip and Knee Osteoarthritis Triaged to a Physiotherapy-Led Clinic at Minimum 5-Year Follow-Up and Factors Associated With Progression to Surgery. The Journal of Arthroplasty. 2020. DOI: 10.1016/j.arth.2020.01.086

[14] Early cartilage lesion and 5-year incident joint surgery in knee osteoarthritis patients: a retrospective cohort study. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07225-3

[15] Knee Osteoarthritis on MRI in Symptomatic Young Adults After ACL Reconstruction From the SUPER-Knee Trial: Feature Prevalence and Association With Early-Stage Clinical Osteoarthritis Criteria. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/23259671261455852

[16] Composite quantitative knee structure metrics predict the development of accelerated knee osteoarthritis: data from the osteoarthritis initiative. BMC Musculoskeletal Disorders. 2020. DOI: 10.1186/s12891-020-03338-7

[17] Association of malalignment, muscular dysfunction, proprioception, laxity and abnormal joint loading with tibiofemoral knee osteoarthritis - a systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2018. DOI: 10.1186/s12891-018-2202-8

[18] The Knee Clinical Assessment Study – CAS(K). A prospective study of knee pain and knee osteoarthritis in the general population. BMC Musculoskeletal Disorders. 2004. DOI: 10.1186/1471-2474-5-4

[19] A Malaysian Delphi consensus on managing knee osteoarthritis. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04381-8

[20] Relevant baseline characteristics for describing patients with knee osteoarthritis: results from a Delphi survey. BMC Musculoskeletal Disorders. 2013. DOI: 10.1186/1471-2474-14-369

[21] Knee pain trajectories over 18 months in non-Hispanic Black and non-Hispanic White adults with or at risk for knee osteoarthritis. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04284-8

[22] Changes in clinical symptoms and functional disability in patients with coexisting patellofemoral and tibiofemoral osteoarthritis: a 1-year prospective cohort study. BMC Musculoskeletal Disorders. 2017. DOI: 10.1186/s12891-017-1486-4

[23] Effect of low-intensity long-duration ultrasound on the symptomatic relief of knee osteoarthritis: a randomized, placebo-controlled double-blind study. Journal of Orthopaedic Surgery and Research. 2018. DOI: 10.1186/s13018-018-0965-0

[24] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > I. Radiographic Evaluation.

[25] Associations between metabolic factors and radiographic knee osteoarthritis in early disease - a cross-sectional study of individuals with knee pain. BMC Musculoskeletal Disorders. 2022. DOI: 10.1186/s12891-022-05881-x

[26] Effects of Running on the Development of Knee Osteoarthritis: An Updated Systematic Review at Short-Term Follow-up. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671231152900

[27] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 11 KNEE ARTHRITIS ASSESSMENT.

[28] Hyaluronic Acid Injections or Oral Nonsteroidal Anti-inflammatory Drugs for Knee Osteoarthritis: Systematic Review and Meta-analysis of Randomized Trials. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967119897909

[29] High prevalence of knee osteoarthritis at a minimum 10-year follow-up after knee dislocation surgery. Knee Surgery, Sports Traumatology, Arthroscopy. 2017. DOI: 10.1007/s00167-017-4443-8

[30] Platelet‐Rich Plasma, Bone Marrow Aspirate Concentrate, and Hyaluronic Acid Injections Outperform Corticosteroids in Pain and Function Scores at a Minimum of 6 Months as Intra‐Articular Injections for Knee Osteoarthritis: A Systematic Review and Network Meta‐analysis. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.01.037

[31] Aaos Comprehensive Orthopaedic Review 3. General Evaluation of the Knee Patient > III. Osteonecrosis.

[32] Risk factors for symptomatic knee osteoarthritis fifteen to twenty‐two years after meniscectomy. Arthritis & Rheumatism. 2004. DOI: 10.1002/art.20489

[33] Orthopaedic Knowledge Update Sports Medicine 6. Nonarthroplasty Management of Osteoarthritis of the Knee > Annotated References.

[34] Aaos Comprehensive Orthopaedic Review 3. General Evaluation of the Knee Patient > I. Osteoarthritis.

[35] Flexion Posteroanterior Radiographs Affect Both Enrollment for and Outcomes After Injection Therapy for Knee Osteoarthritis. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117706692

[36] High tibial osteotomy and concurrent medial meniscus root repair provides improved objective outcomes compared to high tibial osteotomy alone for knee osteoarthritis: A systematic review. Knee Surgery, Sports Traumatology, Arthroscopy. 2025. DOI: 10.1002/ksa.12796

[37] Inadequate Reporting of Complications in Randomized Controlled Trials Cited as Supporting Evidence Underpinning AAOS CPG Recommendations for Hip and Knee Osteoarthritis: Application of the CONSORT Harms Checklist. The Journal of Arthroplasty. 2022. DOI: 10.1016/j.arth.2022.06.004

[38] Intra‐articular injections of platelet‐rich plasma in symptomatic knee osteoarthritis: a consensus statement from French‐speaking experts. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06102-5

[39] Campbell S Operative Orthopaedics 4 Volume Set. TOTAL KNEE ARTHROPLASTY.

[41] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 3Sports Medicine > Image KNEE INJURIES.

[43] The discordance between clinical and radiographic knee osteoarthritis: A systematic search and summary of the literature. BMC Musculoskeletal Disorders. 2008. DOI: 10.1186/1471-2474-9-116

[45] Coronal tibial slope is associated with accelerated knee osteoarthritis: data from the Osteoarthritis Initiative. BMC Musculoskeletal Disorders. 2016. DOI: 10.1186/s12891-016-1158-9

[46] Biologic Therapies for the Treatment of Knee Osteoarthritis. The Journal of Arthroplasty. 2019. DOI: 10.1016/j.arth.2018.12.001

[47] Prevalence of knee osteoarthritis features on magnetic resonance imaging in asymptomatic uninjured adults: a systematic review and meta-analysis. British Journal of Sports Medicine. 2018. DOI: 10.1136/bjsports-2018-099257

[48] Running and Knee Osteoarthritis: A Systematic Review and Meta-analysis. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516657531

[49] Addition of telephone coaching to a physiotherapist-delivered physical activity program in people with knee osteoarthritis: A randomised controlled trial protocol. BMC Musculoskeletal Disorders. 2012. DOI: 10.1186/1471-2474-13-246

[50] Clinical Efficacy of Intra-articular Mesenchymal Stromal Cells for the Treatment of Knee Osteoarthritis: A Double-Blinded Prospective Randomized Controlled Clinical Trial. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546519899923

[51] Meta-Analysis of Adipose Tissue Derived Cell-Based Therapy for the Treatment of Knee Osteoarthritis. Cells. 2021. DOI: 10.3390/cells10061365

[52] Prevalence of hip and knee osteoarthritis in Europe: a systematic review and meta-analysis. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09493-7

[53] Depression in patients with knee osteoarthritis: risk factors and associations with joint symptoms. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-020-03875-1

[54] Relationship between radiographic changes and symptoms or physical examination findings in subjects with symptomatic medial knee osteoarthritis: a three-year prospective study. BMC Musculoskeletal Disorders. 2010. DOI: 10.1186/1471-2474-11-269

[55] Orthopaedic Knowledge Update Sports Medicine 6. Nonarthroplasty Management of Osteoarthritis of the Knee > Summary.

[57] Intra-articular platelet-rich plasma injection for knee osteoarthritis: a summary of meta-analyses. Journal of Orthopaedic Surgery and Research. 2019. DOI: 10.1186/s13018-019-1363-y

[58] Arthroscopic surgery is not superior to conservative treatment in knee osteoarthritis: a systematic review and meta-analysis of randomized controlled trails. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07813-3

[59] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Arthroscopy and Preservation, Knee Reconstruction > Summary.

[60] Artificial intelligence in diagnosis of knee osteoarthritis and prediction of arthroplasty outcomes: a review. Arthroplasty. 2022. DOI: 10.1186/s42836-022-00118-7

[61] Comparing the Predictive Value of Task Performance and Task-Specific Sensitivity During Physical Function Testing Among People With Knee Osteoarthritis. Journal of Orthopaedic & Sports Physical Therapy. 2016. DOI: 10.2519/jospt.2016.6311

[62] Non‐surgical treatments for the management of early osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2016. DOI: 10.1007/s00167-016-4089-y

[63] Artificial intelligence‐based computer‐aided system for knee osteoarthritis assessment increases experienced orthopaedic surgeons’ agreement rate and accuracy. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07220-y

[64] Platelet-Rich Plasma Versus Hyaluronic Acid for Knee Osteoarthritis: A Systematic Review and Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546520909397

[65] Comparison of general practitioners and rheumatologists' prescription patterns for patients with knee osteoarthritis. BMC Musculoskeletal Disorders. 2011. DOI: 10.1186/1471-2474-12-72

[66] Clinical phenotypes of comorbidities in end-stage knee osteoarthritis: a cluster analysis. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07394-1

[67] Long-term effectiveness of intra-articular injectables in patients with knee osteoarthritis: a systematic review and Bayesian network meta-analysis. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-025-05574-w

[68] A Randomized Trial Comparing Arthroscopic Surgery to Non‐surgical Care for Knee Osteoarthritis (OA (SS‐55). Arthroscopy. 2009. DOI: 10.1016/j.arthro.2009.04.054

[69] Intra-articular Injection of Autologous Adipose-Derived Stem Cells or Stromal Vascular Fractions: Are They Effective for Patients With Knee Osteoarthritis? A Systematic Review With Meta-analysis of Randomized Controlled Trials. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465211053893

[70] Bone Marrow Aspirate Concentrate for the Treatment of Knee Osteoarthritis: A Systematic Review. The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211018837

[71] Post-traumatic knee osteoarthritis treated by osteotomy only. Orthopaedics & Traumatology: Surgery & Research. 2010. DOI: 10.1016/j.otsr.2010.06.012

[72] The incidence and characteristics of accelerated knee osteoarthritis among women: the Chingford cohort. BMC Musculoskeletal Disorders. 2020. DOI: 10.1186/s12891-020-3073-3

[74] Non‐surgical management of early knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2011. DOI: 10.1007/s00167-011-1713-8

[76] Is Cooled Radiofrequency Ablation the Hot New Treatment for Knee Osteoarthritis?. Journal of Bone and Joint Surgery. 2020. DOI: 10.2106/jbjs.20.01209

[77] Mesenchymal Stem Cell Implantation in Knee Osteoarthritis: Midterm Outcomes and Survival Analysis in 467 Patients. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120969189

[78] Orthopaedic Knowledge Update Sports Medicine 6. Nonarthroplasty Management of Osteoarthritis of the Knee > Patient Evaluation.

[79] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 12 KNEE ARTHRITIS TREATMENT > CONSENSUS TREATMENT.

[81] Poster 137: Articular Cartilage Debridement Results in Increases in Patient-Reported Outcomes in Large Focal Chondral Defects in the Setting of Mild to Moderate Knee Osteoarthritis. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00234

[82] High identification and positive‐negative discrimination but limited detailed grading accuracy of ChatGPT‐4o in knee osteoarthritis radiographs. Knee Surgery, Sports Traumatology, Arthroscopy. 2025. DOI: 10.1002/ksa.12639

[83] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > MENISCAL INJURIES.

[87] Clinical phenotypes of neuropathic pain and central sensitization in patients with knee osteoarthritis: demographic data, radiographic severity, and pain intensity. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09747-4

[88] Accelerated knee osteoarthritis is associated with pre-radiographic degeneration of the extensor mechanism and cruciate ligaments: data from the Osteoarthritis Initiative. BMC Musculoskeletal Disorders. 2019. DOI: 10.1186/s12891-019-2685-y

[89] Risk factors for progression of radiographic knee osteoarthritis in elderly community residents in Korea. BMC Musculoskeletal Disorders. 2018. DOI: 10.1186/s12891-018-1999-5

[90] Incidence and related risk factors of radiographic knee osteoarthritis: a population-based longitudinal study in China. Journal of Orthopaedic Surgery and Research. 2021. DOI: 10.1186/s13018-021-02577-1

[92] Aaos Comprehensive Orthopaedic Review 3. Anatomy and Biomechanics of the Knee > I. Anatomy.

[93] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 1 KNEE > ANATOMY (FIG. 4.1).

[105] Specific manifestations of knee osteoarthritis predict depression and anxiety years in the future: Vancouver Longitudinal Study of Early Knee Osteoarthritis. BMC Musculoskeletal Disorders. 2020. DOI: 10.1186/s12891-020-03496-8

[106] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > II. Surgical Anatomy of the Knee.

[111] Aaos Comprehensive Orthopaedic Review 3. Knee Dislocations and Patellar Fractures* > I. Knee Dislocations.

[114] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Posterior Knee Anatomy.

[115] Clinical Efficacy Of Intra-articular Mesenchymal Stem Cells For The Treatment Of Knee Osteoarthritis: A Double Blinded, Prospective, Randomized, Controlled Clinical Trial. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120s00127

[120] Short-term results of intra-articular injections of stromal vascular fraction for early knee osteoarthritis. Journal of Orthopaedic Surgery and Research. 2022. DOI: 10.1186/s13018-022-03196-0

[129] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Anatomy > Imaging (Radiograph, MRI, CT Scan, Dynamic Versus Static) > Radiograph.

[133] Efficacy and safety of radiofrequency treatment for improving knee pain and function in knee osteoarthritis: a meta-analysis of randomized controlled trials. Journal of Orthopaedic Surgery and Research. 2022. DOI: 10.1186/s13018-021-02906-4

[135] Body mass index and health-related quality of life of outpatients with knee osteoarthritis: evidence from a cross-sectional study. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-08432-2

[138] Perceptions, beliefs, and needs of Japanese people with knee osteoarthritis during conservative care: a qualitative study. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04641-7

[139] One shot of hyaluronic acid in advanced knee osteoarthritis: postmarketing clinical follow-up for real-world evidence in a pain unit. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-08875-7

[141] Comparison of the efficacy of ultrasound-guided dextrose 25% hypertonic prolotherapy and intra-articular normal saline injection on pain, functional limitation, and range of motion in patients with knee osteoarthritis; a randomized controlled trial. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-08580-5

[142] Bone Marrow Aspirate Concentrate Is Equivalent to Platelet-Rich Plasma for the Treatment of Knee Osteoarthritis at 1 Year: A Prospective, Randomized Trial. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967119900958

[143] Efficacy of platelet-rich plasma and plasma for symptomatic treatment of knee osteoarthritis: a double-blinded placebo-controlled randomized clinical trial. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04706-7

[144] Editorial Commentary: Stem Cell Treatment in Knee Osteoarthritis: What for? Pain Management or Cartilage Regeneration?. Arthroscopy. 2021. DOI: 10.1016/j.arthro.2020.11.017

[146] Medial meniscus tear morphology and related clinical symptoms in patients with medial knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-2939-z

[149] High prevalence of depression in symptomatic knee osteoarthritis: a cross-sectional study on risk factors and therapeutic implications. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-09453-7

[152] Mesenchymal Stem Cell Implantation in Knee Osteoarthritis. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515588317

[154] A Systematic Review of Current Clinical Practice Guidelines on Intra-articular Hyaluronic Acid, Corticosteroid, and Platelet-Rich Plasma Injection for Knee Osteoarthritis: An International Perspective. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/23259671211030272

[155] Bone Marrow Aspirate Concentrate Injections for the Treatment of Knee Osteoarthritis: A Systematic Review of Randomized Controlled Trials. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/23259671241296555

[156] The varying clinical effectiveness of single, three and five intraarticular injections of platelet-rich plasma in knee osteoarthritis. Journal of Orthopaedic Surgery and Research. 2024. DOI: 10.1186/s13018-024-04736-6

[158] Micro‐Fragmented Adipose Tissue Demonstrates Comparable Clinical Efficacy to Other Orthobiologic Injections in Treating Symptomatic Knee Osteoarthritis: A Systematic Review of Level I to IV Clinical Studies. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.03.002

[160] The Functional Outcomes of Patients With Knee Osteoarthritis Managed Nonoperatively at the Joint Clinic at 5-Year Follow-Up: Does Surgical Avoidance Mean Success?. The Journal of Arthroplasty. 2020. DOI: 10.1016/j.arth.2020.04.087

[163] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Knee Anatomy > History and Physical Examination.

[165] How Does Platelet-Rich Plasma Compare Clinically to Other Therapies in the Treatment of Knee Osteoarthritis? A Systematic Review and Meta-analysis. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465211062243

[169] Long-term functional and clinical outcomes of intraarticular double-cross-linked high molecular weight hyaluronic acid (Crespine Gel Plus) injection in knee osteoarthritis: a one year prospective study. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09588-1

[170] The Knee Osteoarthritis Grading System for Arthroplasty. The Journal of Arthroplasty. 2019. DOI: 10.1016/j.arth.2018.11.011

[171] Arthroscopic Debridement of Mild and Moderate Knee Osteoarthritis Results in Clinical Improvement at Short‐Term Follow‐Up: A Systematic Review. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.03.016

[176] Patient Preferences for Surgical Treatment of Knee Osteoarthritis. Journal of Bone and Joint Surgery. 2020. DOI: 10.2106/jbjs.20.00132

[178] Orthopaedic Knowledge Update Sports Medicine 6. Nonarthroplasty Management of Osteoarthritis of the Knee > Nonsurgical Management > Weight Loss.

[187] Regional disparities, age-related changes and sex-related differences in knee osteoarthritis. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07191-w

[191] A Randomized Controlled Single-Blind Study Demonstrating Superiority of Amniotic Suspension Allograft Injection Over Hyaluronic Acid and Saline Control for Modification of Knee Osteoarthritis Symptoms. The Journal of Knee Surgery. 2019. DOI: 10.1055/s-0039-1696672

[195] Can a Convolutional Neural Network Classify Knee Osteoarthritis on Plain Radiographs as Accurately as Fellowship-Trained Knee Arthroplasty Surgeons?. The Journal of Arthroplasty. 2020. DOI: 10.1016/j.arth.2020.04.059

[198] Weak associations between structural changes on MRI and symptoms, function and muscle strength in relation to knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2434-y

[199] Significant improvements in pain after a six-week physiotherapist-led exercise and education intervention, in patients with osteoarthritis awaiting arthroplasty, in South Africa: a randomised controlled trial. BMC Musculoskeletal Disorders. 2016. DOI: 10.1186/s12891-016-1088-6

[201] Orthopaedic Knowledge Update Trauma. Knee Dislocations > Surgical Reconstructions > Complications and Outcomes.

[202] Physical therapy vs internet-based exercise training for patients with knee osteoarthritis: results of a randomized controlled trial. Osteoarthritis and Cartilage. 2018. DOI: 10.1016/j.joca.2017.12.008

[203] Enhancing knee osteoarthritis diagnosis with DMS: a novel dense multi-scale convolutional neural network approach. Journal of Orthopaedic Surgery and Research. 2024. DOI: 10.1186/s13018-024-05352-0

[204] Defining the presence of radiographic knee osteoarthritis: a comparison between the Kellgren and Lawrence system and OARSI atlas criteria. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3205-0

[205] Low grading of the severity of knee osteoarthritis pre-operatively is associated with a lower functional level after total knee replacement. The Bone & Joint Journal. 2014. DOI: 10.1302/0301-620x.96b11.33726

[207] The efficacy of intra-articular triamcinolone acetonide 10 mg vs. 40 mg in patients with knee osteoarthritis: a non-inferiority, randomized, controlled, double-blind, multicenter study. BMC Musculoskeletal Disorders. 2023. DOI: 10.1186/s12891-023-06191-6

[209] Degenerative Meniscus in Knee Osteoarthritis: From Pathology to Treatment. Life. 2022. DOI: 10.3390/life12040603

[210] Long-term Follow-up and Knee Osteoarthritis Change after Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Dislocation. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546507306161

[211] Radiofrequency Ablation in Cooled Monopolar or Conventional Bipolar Modality Yields More Beneficial Short‐Term Clinical Outcomes Versus Other Treatments for Knee Osteoarthritis: A Systematic Review and Network Meta‐Analysis of Randomized Controlled Trials. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.01.048

[212] 10-Year Survival and Clinical Improvement of Meniscal Allograft Transplantation in Early to Moderate Knee Osteoarthritis. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241253849

[214] The Clinical Utility and Diagnostic Performance of Magnetic Resonance Imaging for Identification of Early and Advanced Knee Osteoarthritis. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546511407612

[215] Radiographs and low field MRI (0.2T) as predictors of efficacy in a weight loss trial in obese women with knee osteoarthritis. BMC Musculoskeletal Disorders. 2011. DOI: 10.1186/1471-2474-12-56

[216] Long-Term Survivorship of Closed-Wedge High Tibial Osteotomy for Severe Knee Osteoarthritis: Outcomes After 10 to 37 Years. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/23259671211046964

[217] The effectiveness of exercise therapy and education plus cognitive behavioral therapy, alone or in combination with total knee arthroplasty in patients with knee osteoarthritis – study protocol for the MultiKnee trial. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04924-z

[221] A comparison of Kneipp hydrotherapy with conventional physiotherapy in the treatment of osteoarthritis of the hip or knee: protocol of a prospective randomised controlled clinical trial. BMC Musculoskeletal Disorders. 2009. DOI: 10.1186/1471-2474-10-104

[226] Does the Combination of Platelet-rich Plasma and Supervised Exercise Yield Better Pain Relief and Enhanced Function in Knee Osteoarthritis? A Randomized Controlled Trial. Clinical Orthopaedics & Related Research. 2024. DOI: 10.1097/corr.0000000000002993

[228] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 12 KNEE ARTHRITIS TREATMENT > HTO.

[233] Development of machine learning models aiming at knee osteoarthritis diagnosing: an MRI radiomics analysis. Journal of Orthopaedic Surgery and Research. 2023. DOI: 10.1186/s13018-023-03837-y

[237] Association between vitamin D deficiency, inflammatory markers, and knee osteoarthritis: a retrospective study. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-025-05805-0

[239] Platelet‐rich plasma injections for the management of knee osteoarthritis: The ESSKA‐ICRS consensus. Recommendations using the RAND/UCLA appropriateness method for different clinical scenarios. Knee Surgery, Sports Traumatology, Arthroscopy. 2024. DOI: 10.1002/ksa.12320

[242] Winner of the 2008 Systematic Review Competition: Knee Osteoarthritis after Anterior Cruciate Ligament Injury. The American Journal of Sports Medicine. 2009. DOI: 10.1177/0363546509338827

[244] Efficacy of strength and aerobic exercise on patient-reported outcomes and structural changes in patients with knee osteoarthritis: study protocol for a randomized controlled trial. BMC Musculoskeletal Disorders. 2013. DOI: 10.1186/1471-2474-14-266

[245] Adding microfracture to an SVF‐based arthroscopic pathway was associated with greater 24‐month improvements in pain, function and MRI cartilage morphology in KL II–III knee osteoarthritis: A randomized controlled trial. Knee Surgery, Sports Traumatology, Arthroscopy. 2026. DOI: 10.1002/ksa.70377

[249] Campbell S Operative Orthopaedics 4 Volume Set. UNICOMPARTMENTAL KNEE ARTHROPLASTY.

[250] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 15 REVISION TOTAL KNEE ARTHROPLASTY > PREOPERATIVE EVALUATION.

[253] Longitudinal correlation between X‐ray and MRI findings in medial compartment knee osteoarthritis: Insights into early cartilage loss and structural changes. Knee Surgery, Sports Traumatology, Arthroscopy. 2025. DOI: 10.1002/ksa.70016

[254] Risk factors for joint replacement in knee osteoarthritis; a 15-year follow-up study. BMC Musculoskeletal Disorders. 2017. DOI: 10.1186/s12891-017-1871-z

[255] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Knee > II. Osteotomy.

[256] Campbell S Operative Orthopaedics 4 Volume Set. INDICATIONS AND CONSIDERATIONS FOR PATELLAR RESURFACING IN PRIMARY TOTAL KNEE ARTHROPLASTY.

[257] Ultrasonographic echo intensity in the medial femoral cartilage is enhanced prior to cartilage thinning in women with early mild knee osteoarthritis. Knee Surgery, Sports Traumatology, Arthroscopy. 2023. DOI: 10.1007/s00167-023-07440-w

[258] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > OSTEOCHONDRAL LESIONS > 3. Osteonecrosis.

[260] Micro‐fragmented adipose tissue (mFAT) associated with arthroscopic debridement provides functional improvement in knee osteoarthritis: a randomized controlled trial. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07101-4

[262] Aaos Comprehensive Orthopaedic Review 3. Nonarthroplasty Surgical Treatment of the Knee > IV. Knee Arthrodesis.

[263] Upper tibial MRI vascular marks lost in early knee osteoarthritis. Journal of Orthopaedic Surgery and Research. 2018. DOI: 10.1186/s13018-018-0991-y

[264] The Gut Microbiome and Joint Microbiome Show Alterations in Patients With Knee Osteoarthritis Versus Controls: A Systematic Review. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.05.010

[265] An MRI-based radiomics framework for early identification and progression stratification in knee osteoarthritis: data from the osteoarthritis initiative. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-09234-2

[267] Association between statins and progression of osteoarthritis features on magnetic resonance imaging in a predominantly pre-radiographic cohort: the Vancouver Longitudinal Study of Early Knee Osteoarthritis (VALSEKO): a cohort study. BMC Musculoskeletal Disorders. 2022. DOI: 10.1186/s12891-022-05900-x

[269] Is conventional magnetic resonance imaging superior to radiography in the functional integrity evaluation of anterior cruciate ligament in patients with knee osteoarthritis?. Arthroplasty. 2024. DOI: 10.1186/s42836-024-00262-2

[270] Severity of valgus knee osteoarthritis has no effect on clinical outcomes after total knee arthroplasty. Archives of Orthopaedic and Trauma Surgery. 2021. DOI: 10.1007/s00402-021-03785-4

[272] Anterior cruciate ligament reconstruction with 4‐strand hamstring autograft and accelerated rehabilitation: a 10‐year prospective study on clinical results, knee osteoarthritis and its predictors. Knee Surgery, Sports Traumatology, Arthroscopy. 2012. DOI: 10.1007/s00167-012-2234-9

[273] Estradiol and its metabolites and their association with knee osteoarthritis. Arthritis & Rheumatism. 2006. DOI: 10.1002/art.22005

[274] Progression to arthroplasty surgery among patients with hip and knee osteoarthritis. The Bone & Joint Journal. 2022. DOI: 10.1302/0301-620x.104b7.bjj-2021-1766.r1

[275] Symptomatic relief in medial opening wedge high tibial osteotomies for the treatment of knee osteoarthritis is influenced by concurrent procedures and preoperative pain level. Journal of ISAKOS. 2018. DOI: 10.1136/jisakos-2017-000169

[276] Poor Performance on Single-Legged Hop Tests Associated With Development of Posttraumatic Knee Osteoarthritis After Anterior Cruciate Ligament Injury. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118810775

[277] Randomised, double-blind comparison of a fixed co-formulation of intra-articular polynucleotides and hyaluronic acid versus hyaluronic acid alone in the treatment of knee osteoarthritis: two-year follow-up. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04648-0