Anatomy

Knee joint anatomy and biomechanics, focusing on trochlear geometry, ligamentous stability, and the impact of malalignment on surgical planning.

Overview

Knee surgery requires a deep anatomical and functional understanding to restore individual patient anatomy, as successful outcomes depend more on this understanding than on surgical technique alone [79]. The range of knee anatomy in patients scheduled for total knee arthroplasty is wide [72], and existing arthroplasty techniques are based on assumptions that may not adequately address morphologic outliers, potentially leading to dissatisfaction [60]. Newer surgical techniques should not be assumed superior to older ones without sufficient time to evaluate outcomes [79].

Lateral unicondylar knee arthroplasty is technically more challenging than medial unicondylar knee arthroplasty due to lower indication numbers and the functional anatomy of the lateral compartment [12]. Unicompartmental and bicompartmental arthroplasty with a finned metal tibial-plateau implant has a place in reconstructive surgery of the arthritic knee joint with proper indications [76]. Around-the-knee osteotomies correct coronal, sagittal, and axial plane deformities around the knee [66]. Trochleoplasty should be performed as a primary procedure with clear indications, not as a secondary or revision procedure [20].

Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [14]. Clinical results of total knee arthroplasty using hinge joints generally depend on implant design, appropriate technical use, and adequate indications [16]. A thorough knowledge of anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [69]. Advanced microfracture techniques for isolated patellar chondral defects show promise, but indications and variability in techniques need elucidation in higher-level studies [13]. Partial patellar lateral facetectomy via arthroscopic technique is minimally invasive and allows for diagnostic evaluation and treatment of concurrent intra-articular pathology [88].

Anatomy & Pathophysiology

Osseous Morphology and Alignment

The morphology of the proximal femur strongly correlates with the geometry of the distal femoral trochlea, representing a factor of clinical importance for physiological knee kinematics and kinematic knee replacement concepts [58]. Morphologic variations in the tibia and femur influence the kinematics of the knee and contribute to the risk of anterior cruciate ligament injury as well as function of the knee after injury and after surgical reconstruction [92]. The 3D analysis of the sagittal curvature of the femoral trochlea in the Chinese population may improve understanding of knee kinematics and development of physiological knee prostheses [53]. Knee alignment is different in different individuals and is dynamic in nature, changing with different postures [56]. The functional knee phenotype concept better represents the variability of the coronal knee alignment than the conventional system of valgus, varus and neutral [96].

Ligamentous Anatomy and Biomechanics

The chapter provides a comprehensive review of the anatomy and biomechanics of the knee, including bone structure, vascular and nerve supply, ligamentous organization, and functional mechanics relevant to stability and injury [65]. The bone attachments of the medial collateral and posterior oblique ligaments are defined anatomically and radiographically, facilitating repairs and reconstructions that restore physiological laxity and stability patterns across the arc of knee flexion [102]. The fibula is a dynamic bone important for the kinematics and kinetics of the knee and ankle joints [51]. Standardized testing protocols and techniques characterize the biomechanical behavior of the knee and cruciate ligaments to allow comparisons between investigations [52]. Biomechanical studies determine the magnitude and direction of forces and moments of various tissues in and around a diarthrodial joint, as well as measure corresponding joint kinematics, to assist clinicians in assessing function and planning treatment [91].

Kinematics and Reconstruction Outcomes

Kneeling involves differences in rotational kinematics between the flexion phase and the extension phase [44]. Neither all-epiphyseal nor over-the-top pediatric reconstruction techniques restore the contact mechanics and kinematics of the ACL-intact knee [47]. Posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics under physiologic loading conditions [59]. Isometric grafts restore normal knee kinematics regardless of the flexion angle at which they are secured [85]. Anchor repair of biceps femoris is similar to knotless tunnel repair in laboratory conditions, with no statistically significant differences between the two constructs regarding restoration of knee kinematics [61]. Failure to treat all injured structures in high-grade multiligamentous knee injuries can lead to changes in knee kinematics and poorer outcomes [82]. Comparative anatomical studies suggest that understanding shared kinematic principles can improve the design of external bracing systems and total knee replacements [99].

Evaluation and Surgical Planning

Gait and fluoroscopic analysis methods can evaluate knee joint mechanical parameters such as stress distribution at the joint contact interface [89]. A knee joint simulator successfully demonstrated the anatomy, physiology, and kinematics of knee ligaments, allowed teaching of ligamentous instability tests, and demonstrated the effect of knee ligament reconstructive surgery [93]. Individualisation of knee arthroplasty based on patient anatomy, physiology, and kinematics is the future direction of knee arthroplasty techniques [78].

Classification

Posterior Tibial Slope (PTS): Anatomic variants with a PTS ≥12° are very uncommon (≤3%) and can be considered pathological [7].

ACL Bundle Insertions: The topographical alignment of anterior cruciate ligament (ACL) bundle insertions varies widely, suggesting that historical anteromedial and posterolateral terminology should not be used routinely [15].

Anterolateral Ligament (ALL): Anatomic studies identify two distinct structures described as the superficial and deep anterior lateral ligament (ALL), consistent with previous conflicting descriptions [17].

ACL Tibial Insertion Shape: A classification system for the shape of the tibial insertion site of the ACL is a repeatable and reliable tool, and consideration of individual shape is required to prevent iatrogenic damage and ensure proper footprint restoration [43].

Tibial Plateau Fractures: Three-dimensional computed tomography imaging increases the reliability of classification systems for tibial plateau fractures [48].

Medial Meniscus Ramp Tears: A surgically relevant classification system for medial meniscus ramp tears, based on tear morphology, allows for the evaluation of differing repair patterns and their effects on postoperative clinical outcomes [49].

Pes Anserinus Morphology: A proposed classification of pes anserinus morphology may improve the planning of surgical procedures [54].

Medial Knee Layers: The supporting structures and layers on the medial side of the knee follow a consistent three-layered anatomical pattern, suggesting the use of specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament' [55].

Lower-Extremity Length Discrepancies: The classification of developmental patterns in lower-extremity length discrepancies illustrates varying directional changes and their dependence on underlying biological phenomena [64].

Arthritic Knee Phenotypes: CT-based phenotyping established a 3D classification of arthritic knee anatomy into 4 foundational morphologies, with types 1 and 3 representing outliers present in 26% of knees undergoing total knee arthroplasty (TKA) [84].

Clinical Presentation

A thorough understanding of the anatomy, physical examination findings, and imaging characteristics aids in the management of posteromedial corner injuries [5]. Three-dimensional images of the posteromedial corner of the knee help in understanding its anatomy [1]. Knowledge of the anatomy and function of the patellofemoral joint is essential to treat all different pathologies appropriately [6].

History and Inspection: Distinct malformations in nail patella syndrome are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology essential in treatment [34]. An unusual gastrocnemius muscle syndrome represents a definite clinical syndrome associated with a specific anatomical lesion that is amenable to surgical repair [35]. A new symptomatic intra-articular cord-like structure associated with discoid meniscus is an important differential diagnosis to symptoms usually referred to as meniscus pathology [28].

Palpation and Special Tests: Knowledge of the prevalence, size, shape, and location of the semimembranosus-tibial collateral ligament bursa aids in the differential diagnosis of medial knee pain [33]. Instability of the proximal tibiofibular joint is rarely reported and often missed; understanding its etiology, symptoms, and anatomic variations is essential for evaluating symptomatic patients [31]. The anterolateral ligament of the human knee is consistently present [42].

Imaging and Diagnostic Modalities: Characteristic MR features of common and uncommon disorders cause anterior knee pain, aiding radiologists in identifying typical imaging patterns for accurate diagnosis and appropriate therapy [8]. Ultrasound is able to localize the site of nerve lesion and characterize it from a morphological point of view, adding information about nerve involvement to improve diagnostic ability and therapeutic decision-making in fibular neuropathy at the knee [29]. The diagnosis of idiopathic osteonecrosis of the patella was confirmed with radiographs, a radioisotopic bone scan, conventional tomograms, and histological examination after excision [10].

Anatomic Variants and Red Flags: An aberrant branch of the long head of the biceps tendon represents an anatomic variant that has not been previously described [9]. The anterior meniscofemoral ligament of the medial meniscus is an anomaly not usually associated with clinical symptoms and should not be routinely excised when encountered [30]. An aberrant anterior tibial artery does not depend on the patient's morphotype, the lumen diameter is highly variable, and its clinical impact has yet to be determined [32]. Anatomic variants with a posterior tibial slope (PTS) ≥12° are very uncommon (≤3%) and could be considered pathological [7].

Investigations

Plain radiography: Plain radiographs are appropriate initial imaging studies for most knee conditions [41]. Comprehensive qualitative and quantitative guidelines for assessing posterolateral knee structures on both anteroposterior and lateral knee radiographs have been described [95]. Medial meniscus horn position can be precisely and reproducibly defined on radiographs [74]. Posterolateral rim morphology can be delineated on lateral plain film images, with radiographic type 1 rims correlating with distinct anatomic morphology and radiographic type 2 rims correlating with indistinct morphology [75]. Most commonly utilized radiographic measures of elbow anatomy were consistent between sexes, across the adolescent age group, and between adolescents and young adults [67]. Focusing on bone morphology allows surgeons to easily perform visual assessment using preoperative radiographs for the effect of tibial plateau morphology on joint line convergence angle in medial open wedge high tibial osteotomy [86]. MRIs predict anterior cruciate ligament length more reliably than radiographs [101]. A variety of reliable skeletal maturity estimation systems using routine knee radiographs and MRI are described for planning surgeries about the knee, allowing orthopaedic surgeons to inform preoperative workups without requiring additional hand radiographs [104].

MRI: Magnetic resonance imaging is recommended as a routine imaging method for accurate diagnosis and appropriate treatment of bone stress injuries causing exercise-induced knee pain [40]. MRI is the diagnostic procedure of first choice for synovial hemangioma of the knee joint with cystic invasion of the femur [45]. MR imaging is the imaging technique of choice for a complete supra-patellar plica, although it has limitations [46]. MRI is of crucial significance for operative planning and distinguishing benign from malignant soft-tissue tumors in cases of ganglion of the superior tibiofibular joint [94]. Three-dimensional imaging of the posteromedial corner of the knee aids in understanding its anatomy [1]. The integrity of Kaplan fibers should be routinely reviewed on MRI scans [77]. Anatomical, MRI-based parameters such as increased tibial tubercle-trochlear groove and patellar height indicate a higher risk of recurrent patellar dislocation following medial reefing [73].

CT: Advanced imaging such as CT, MRI, and nuclear medicine provide enhanced detail for specific soft tissue, bone, and implant assessments [41].

Bone scan: Diagnosis of idiopathic osteonecrosis of the patella was confirmed with radiographs, a radioisotopic bone scan, conventional tomograms, and histological examination after excision [10].

Tomosynthesis: Diagnosis of idiopathic osteonecrosis of the patella was confirmed with radiographs, a radioisotopic bone scan, conventional tomograms, and histological examination after excision [10].

Aspiration: Diagnosis of idiopathic osteonecrosis of the patella was confirmed with radiographs, a radioisotopic bone scan, conventional tomograms, and histological examination after excision [10].

Laboratory: Diagnosis of idiopathic osteonecrosis of the patella was confirmed with radiographs, a radioisotopic bone scan, conventional tomograms, and histological examination after excision [10].

Other Considerations: MR imaging presents characteristic features of common and uncommon disorders causing anterior knee pain to aid radiologists in identifying typical imaging patterns for accurate diagnosis and appropriate therapy [8]. A thorough understanding of anatomy, physical examination findings, and imaging characteristics aids in the management of posteromedial corner injuries [5]. Advanced imaging should be used to augment a history and examination when necessary but should not replace a thorough history and physical examination [18]. Selective magnetic resonance imaging does not provide enhanced diagnostic utility over clinical examination in children and adolescents, particularly when the clinical diagnosis is uncertain and MRI input will alter the treatment plan [83].

Treatment

Non-Operative Management

Functional management is recommended for non-athletic patients with partial anterior cruciate ligament (ACL) tears who do not have a meniscal lesion [21]. Nonoperative treatment options are highlighted for hamstring injuries, with surgical decision-making based on patient presentation and injury patterns [114]. For neonatal leg fracture and constriction ring syndrome, nonoperative treatment may allow the fracture to heal but requires close monitoring of limb vascularisation [109]. Moderate nonprogressive coxa vara in childhood often does not require surgery [110]. Conservative management is adopted for anomalous insertion of anterior and posterior horns of the medial meniscus in patients with mild complaints, skeletal immaturity, and remaining growth [103]. Nonoperative treatment for apophysitis of the proximal patella should be the initial management approach [97].

Conversely, non-operative treatments for lower-extremity rotational problems in children are usually ineffective [71]. Nonoperative management of proximal rectus femoris avulsion injuries is associated with highly variable periods of convalescence, poor return to preinjury level of function, and high risk of injury recurrence [107]. Conservative management failure to ameliorate symptoms in patients with a subchondral cyst in the lateral condyle of the femur is an indication for intraosseous bioplasty [111].

Operative Management

Indications: Surgical treatment may be recommended for partial ACL tears in patients other than non-athletic patients without meniscal lesions [21]. Surgery is indicated for apophysitis of the proximal patella when the diagnosis is in doubt [97]. Surgical management is indicated for progressive, painful, unilateral coxa vara deformity or leg-length discrepancy in childhood [110]. An algorithmic approach to diagnosis and treatment is important for avulsions of the distal femur and proximal tibia in children and adolescents due to the heterogeneity of treatment and outcomes [68]. Proximal femoral focal deficiency/congenital femoral deficiency is best treated by clinicians with considerable deformity treatment experience to maximize functional outcomes [80].

Surgical Approach / Technique: Anatomical anterior cruciate ligament reconstruction results in fewer rates of atraumatic graft rupture and higher rates of rotatory knee stability compared to non-anatomical approaches, although overall failure rates are similar [50]. Conventional non-anatomic anterior cruciate ligament reconstruction techniques do not prevent early osteoarthritis nor restore normal dynamic knee function [87]. Trochleoplasty should be performed as a primary procedure with clear indications rather than as a secondary or revision procedure [20]. Repair of horizontal cleavage meniscus tears results in substantial improvements in patient-reported outcomes, acceptable midterm clinical healing rates, and low reoperation/failure rates [62]. Debridement of mucoid tissue is a safe and effective treatment method for mucoid degeneration of the posterior cruciate ligament [63]. Single soft tissue graft reconstruction of the fibular collateral ligament and posterolateral corner demonstrates satisfactory clinical and functional outcomes [90]. Surgical release is effective for innervation supply issues of the vastus medialis muscle in cases where nonoperative treatment failed [105]. Surgical correction can be effective for subluxating biceps femoris tendon if patient symptoms are unresponsive to nonoperative treatment [112].

Implant Selection: Clinical results for total knee arthroplasty using hinge joints generally depend on implant design, appropriate technical use, and adequate indications [16]. The use of nonorthotopic osteochondral allografts is an acceptable practice that can reliably restore the articular surface within a suitable range [3]. Advanced microfracture techniques for cartilage restoration in isolated patellar chondral defects show promise, but indications and variability in techniques need elucidation in higher-level studies [13].

Alignment / Balancing Strategy: Kinematic alignment for total knee arthroplasty requires further evaluation to specify thresholds for acceptable alignment [2]. Modern studies are needed to evaluate clinical outcomes for medial closing-wedge proximal tibia osteotomy in the valgus knee, though the procedure is considered a reproducible and effective treatment option to reduce pain and improve function in younger patients [57]. Lateral unicondylar knee arthroplasty is technically more challenging than medial unicondylar knee arthroplasty due to the lower number of indications and the functional anatomy of the lateral compartment [12].

Other Considerations: Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [14]. Anatomic anterolateral ligament reconstruction of the knee leads to overconstraint at any fixation angle, and the surgical technique and indications should be investigated further with caution [81].

Complications

Other Considerations: Kinematic alignment for total knee arthroplasty requires further evaluation to specify thresholds for acceptable alignment [2]. Most studies have failed to show improved short-term clinical outcomes when adding cartilage restoration procedures to high tibial osteotomy, raising questions about whether longer-term studies will show improved efficacy [113]. More trials and long-term evidence are needed for anterior knee pain and patellofemoral osteoarthritis [108].

Nonorthotopic Osteochondral Allografts: The long-term effects of nonorthotopic osteochondral allografts on graft survivorship and clinical outcomes require further clinical investigation [3]. High-quality prospective studies are needed to evaluate the efficacy and long-term outcomes of nonorthotopic osteochondral allografts [4].

Autologous Matrix-Induced Chondrogenesis: Further studies with long-term follow-up are needed to determine whether the grafted area in Autologous Matrix-Induced Chondrogenesis maintains structural and functional integrity over time [11].

Adamantinoma: Early aggressive treatment and long-term follow-up are mandatory for metastasis of adamantinoma after knee disarticulation [24].

Myositis Ossificans: Myositis ossificans in the newborn can undergo extensive remodeling with almost normal bone morphology at follow-up despite an atypical anatomical site and rapid course [27].

Recovery

The evidence base for recovery trajectories and long-term outcomes is heterogeneous, spanning various pathologies and surgical interventions. While specific functional milestones and validated PROM trajectories are not detailed in the current data, several studies provide insight into outcome plateaus and prognostic factors.

Light activity (weeks): Specific timelines for light activity, such as desk work or driving, are not defined in the provided evidence.

Full activity (months): Long-term follow-up data indicates that computer navigated lateral opening wedge distal femoral osteotomy yields satisfactory clinical outcomes and 79% survivorship [22]. In contrast, the natural course of chronic exertional compartment syndrome of the lower leg appears to involve persistent symptoms over time [118].

Complete recovery / outcome plateau (months): Prognostic stability varies by pathology. The prognosis after excision of localized pigmented villonodular synovitis of the knee is excellent, with no recurrences observed [122]. For patellar instability in patients with low-grade trochlear dysplasia, MPFL reconstruction provides satisfactory outcomes without remarkable arthritic changes at mid-term follow-up [106]. However, although there is favorable initial evolution at 30 months after a complete ACL lesion, the re-rupture rate or 'scar tissue' rupture is 40% at a mean follow-up of 8 years [125]. In the late multiple ligament and posterolateral corner-reconstructed knee, the presence of chondrosis at the time of surgery is an important prognosticator of functional outcome at intermediate follow-up [123]. At 2-year follow-up, no clinically significant differences are observed between different CPAK phenotypes after medial opening-wedge high tibial osteotomy [124]. Despite progressive radiological grading of osteoarthritis at long-term follow-up, functional outcomes after surgical treatment of intra-articular tibial plateau fractures in skiers are very satisfactory [98].

Rehabilitation protocol: Specific rehabilitation protocols, including PT phasing, immobilisation duration, and weight-bearing progression, are not specified in the available evidence.

Functional milestones: Validated PROM trajectories or outcome-measure benchmarks are not explicitly reported in the provided data.

Other Considerations: Several areas require further investigation to define recovery parameters. Kinematic alignment for total knee arthroplasty requires further evaluation to specify thresholds for acceptable alignment [2]. High quality prospective studies are needed to evaluate the efficacy and long-term outcomes of nonorthotopic osteochondral allografts [3, 4]. Further studies with long-term follow-up are needed to determine whether the grafted area maintains structural and functional integrity after Autologous Matrix-Induced Chondrogenesis [11]. Further studies are required to understand if two incision technique femoral tunnel placement in anterior cruciate ligament reconstruction can ameliorate proprioception and clinical outcome at long-term follow-up [100]. The heterogeneity of pathology treated, follow-up time, and outcome measures limits comparison between studies on clinical outcomes of high tibial osteotomy for knee instability [119].

Additional prognostic and anatomical context includes: Femoral component coronal alignment in fixed-bearing unicompartmental knee arthroplasty may affect long-term clinical outcomes but does not affect short-term clinical outcomes or 10-year survivorship [19]. The bone microstructure from anterior cruciate ligament footprints is similar after ligament reconstruction and does not affect long-term stability of the operated knee joint [23]. Early aggressive treatment and long-term follow-up are mandatory for metastasis of adamantinoma [24]. The article examines the evolution of the anatomical description of the ulnar tunnel and its relevant clinical associations [25]. Histological evolution of the synovial membrane and synovial fluid by disease progresses from slight activity and vascularization in early stages to marked fibrosis, multistratified intima, and vascular proliferation in chronic cases [26]. Myositis ossificans in the newborn underwent extensive remodeling with almost normal bone morphology at follow-up [27]. Paget's disease in the tibia showed faster longitudinal growth during the first six years before slowing as the disease extended to involve the entire bone [120]. The prognosis for spontaneous recovery without specific treatment is relatively good in most instances, but permanent epiphyseal growth changes may take place occasionally [121].

Key Evidence

• [L5] Three-dimensional images of these structures can help better understanding its anatomy. (10.1007/s00167-011-1615-9)
• [Paper] While its short-term clinical results are encouraging, it must be evaluated further and the thresholds for acceptable alignment still need to be specified. (10.1016/j.otsr.2020.102773)
• [L5] The use of nonorthotopic osteochondral allografts is an acceptable practice that can reliably restore the articular surface within a suitable range, though further clinical investigation is necessary to determine long-term effects on graft survivorship and clinical outcomes. (10.1016/j.arthro.2018.08.009)
• [L5] High quality prospective studies are needed to evaluate efficacy and long-term outcomes. (10.1016/j.arthro.2017.01.005)
• [L5] A thorough understanding of the anatomy, physical examination findings, and imaging characteristics will aid the physician in the management of these injuries. (10.5435/jaaos-d-16-00020)
• [L5] A knowledge base of the anatomy and function is essential to treat all different pathologies appropriately. (10.1007/s00167-005-0683-0)
• [L3] Anatomic variants with a PTS ≥12° were very uncommon (≤3%) and could be considered pathological. (10.1177/2325967119895258)
• [L4] This pictorial essay presents the characteristic MR features of common and uncommon disorders causing anterior knee pain to aid radiologists in identifying typical imaging patterns for accurate diagnosis and appropriate therapy. (10.1007/s00167-012-1976-8)
• [L4] The anomaly represents an anatomic variant that has not been previously described. (10.1016/j.jse.2011.01.036)
• [L4] However, further studies with long-term follow-up are needed to determine whether the grafted area will maintain structural and functional integrity over time. (10.1007/s00167-010-1042-3)
• [L4] Lateral UKA is technically more challenging than medial UKA due to the lower number of indications and the functional anatomy of the lateral compartment. (10.1007/s00264-013-2222-9)
• [L4] Advanced microfracture techniques showed promise, but indications and variability in techniques need to be elucidated in higher-level studies. (10.1177/23259671231153422)
• [L5] Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques are essential for safe and effective aspiration and injection. (10.5435/jaaos-d-16-00762)
• [L5] The topographical alignment of the separate bundles is varied on a very wide range, suggesting that the historical anteromedial and posterolateral terminology should not be used routinely. (10.1007/s00167-008-0552-8)
• [L4] Clinical results generally depend on implant design, appropriate technical use, and adequate indications. (10.1302/2058-5241.4.180056)
• [L5] This anatomic study clearly identified 2 structures, described as the superficial and deep ALL, which were consistent with previous but conflicting descriptions of the ALL. (10.1177/2325967116675604)
• [L5] Advanced imaging should be used to augment a history and examination when necessary but should not replace a thorough history and physical examination. (10.5435/jaaos-d-15-00463)
• [L3] Femoral component coronal alignment may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. (10.1016/j.arth.2020.07.070)
• [L5] Trochleoplasty should not be performed as a secondary or revision procedure but rather as a primary procedure with clear indications. (10.1016/j.arthro.2020.05.050)
• [L1] Functional management may be recommended in non-athletic patients without meniscal lesion, but surgical treatment may be recommended in other patients. (10.1016/j.otsr.2012.09.013)
• [L4] Computer navigated DFLOWO has satisfactory clinical outcomes and 79% survivorship in long-term follow-up. (10.1177/2325967120s00527)
• [L2] The bone microstructure is not dependent on the time from injury to surgery and has no impact on the long-term stability of the operated knee joint. (10.1007/s00167-021-06493-z)
• [L4] Early aggressive treatment and long-term follow-up are mandatory. (10.2106/00004623-198668050-00023)
• [L5] This article examines the evolution of the anatomical description of the ulnar tunnel and its relevant clinical associations, casting light on the life and contributions of Guyon. (10.1016/j.jhsa.2014.09.026)
• [L4] It describes histological evolution from slight activity and vascularization in early stages to marked fibrosis, multistratified intima, and vascular proliferation in chronic cases. (10.2106/00004623-196446040-00026)
• [Case_report] Despite the atypical anatomical site and rapid course, the lesion underwent extensive remodeling with almost normal bone morphology at follow-up. (10.2106/00004623-198668030-00023)
• [L4] This ligamentous structure is an important differential diagnosis to symptoms usually referred to as meniscus pathology. (10.1016/j.arthro.2005.12.023)
• [Case_report] Ultrasound is able to localize the site of nerve lesion and characterize it from a morphological point of view, adding information about nerve involvement to improve diagnostic ability and therapeutic decision-making. (10.1007/s00167-017-4601-z)
• [L4] This anomaly is not usually associated with clinical symptoms and should not be routinely excised when encountered. (10.1177/0363546503261712)
• [L5] Instability of the proximal tibiofibular joint is rarely reported and often missed; understanding its etiology, symptoms, and anatomic variations is essential for evaluating symptomatic patients. (10.5435/00124635-200303000-00006)
• [L3] The patient's morphotype did not influence its presence, the lumen diameter is highly variable and its clinical impact has yet to be determined. (10.1002/ksa.12435)
• [L5] Knowledge of its prevalence, size, shape, and location aids in the differential diagnosis of medial knee pain. (10.2106/00004623-199409000-00007)
• [L4] These distinct malformations are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology essential in treatment. (10.1302/0301-620x.98b4.37025)
• [L4] The case represents a definite clinical syndrome associated with a specific anatomical lesion that is amenable to surgical repair. (10.2106/00004623-197355060-00016)
• [L4] Magnetic resonance imaging is recommended as a routine imaging method for accurate diagnosis and appropriate treatment. (10.1177/0363546505278699)
• [L5] The anterolateral ligament is consistently present. (10.1007/s00167-011-1580-3)
• [L3] The classification system is a repeatable and reliable tool, and consideration of individual shape is required to prevent iatrogenic damage and ensure proper footprint restoration. (10.1007/s00167-015-3891-2)
• [L4] In kneeling, there was a difference in the rotational kinematics between the flexion phase and the extension phase. (10.1186/s13018-022-03080-x)
• [Case_report] MRI is the diagnostic procedure of first choice, and surgical resection with bone grafting is an effective treatment. (10.1007/s00402-008-0690-y)
• [L4] Although MR imaging is the imaging technique of choice, it still has limitations as demonstrated in this case. (10.1007/s00167-006-0037-6)
• [L5] However, neither restored the contact mechanics and kinematics of the ACL-intact knee. (10.1177/0363546513483269)
• [Paper] This finding seems to show that more sophisticated imaging techniques can improve the reliability of fracture classification systems. (10.1016/j.injury.2009.02.015)
• [L4] This classification system allows for the ability to evaluate differing repair patterns and their effects on postoperative clinical outcomes. (10.1177/2325967125s00101)
• [L1] The overall failure rate was similar between the anatomical and non-anatomical approaches. (10.1136/jisakos-2020-000476)
• [L5] The study concludes that the fibula is a dynamic bone important for the kinematics and kinetics of the knee and ankle joints. (10.1007/s00402-005-0054-9)
• [L5] Standardized testing protocols and techniques are proposed to characterize the biomechanical behavior of the knee and cruciate ligaments to allow comparisons between investigations. (10.1007/s001670050226)
• [L4] The results of the current study may be helpful to improve the understanding of the knee kinematics and develop the physiological knee prostheses. (10.1007/s00167-011-1679-6)
• [L5] The planning of surgical procedures may be improved by the proposed classification. (10.1007/s00167-018-5318-3)
• [L5] The study delineated a consistent three-layered anatomical pattern of the medial knee, suggesting the use of specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament'. (10.2106/00004623-197961010-00011)
• [L4] Knee alignment is different in different individuals and is dynamic in nature, changing with different postures. (10.1302/0301-620x.97b4.33740)
• [Paper] Although modern studies are needed to evaluate the clinical outcomes using this technique, the authors believe this procedure is a reproducible and effective treatment option to reduce pain and improve function in a younger patient population in whom arthroplasty is less desirable. (10.1016/j.eats.2020.03.008)
• [L3] In order to improve knowledge on the physiological kinematics of the knee joint and to improve the concept of kinematic knee replacement, the proximal femur seems to be a factor of clinical importance. (10.1007/s00167-014-3343-4)
• [L5] Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics. (10.1177/03635465030310040901)
• [L3] Existing arthroplasty techniques are based on assumptions that may not adequately address the anatomy of morphologic outliers and could lead to dissatisfaction. (10.1007/s00167-021-06725-2)
• [L5] No statistically significant differences were found between the two constructs regarding restoration of knee kinematics, mean failure loads, or stiffness. (10.1177/23259671251385225)
• [L3] There were substantial improvements in patient-reported outcomes, showing acceptable midterm clinical healing rates and low reoperation/failure rates. (10.1016/j.arthro.2020.12.150)
• [Case_report] Debridement of the mucoid tissue is a safe and effective treatment method. (10.1007/s00167-009-0885-y)
• [L4] The classification of developmental patterns illustrates the varying directional changes that can occur in lower-extremity length discrepancies and their dependence on underlying biological phenomena. (10.2106/00004623-198264050-00001)
• [L4] The review examines indications, surgical techniques, and outcomes for correcting coronal, sagittal, and axial plane deformities around the knee. (10.1016/j.jisako.2024.04.002)
• [L4] Most commonly utilized radiographic measures were consistent between sexes, across the adolescent age group, and between adolescents and young adults. (10.1016/j.jse.2011.10.026)
• [L4] The heterogeneity of the treatment and outcomes highlights the importance of developing an algorithmic approach to diagnosis and treatment. (10.1177/2325967119s00068)
• [L5] A thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs despite careful planning and adherence to proper surgical technique. (10.1177/2325967116652122)
• [L4] Non-operative treatments are usually ineffective, and while rotational osteotomies are effective, they are associated with significant complication rates. (10.2106/00004623-198567050-00027)
• [L1] The range of knee anatomy in patients scheduled for TKA is wide. (10.1016/j.arth.2017.02.028)
• [L3] Anatomical, MRI-based parameters should be considered before indicating medial reefing. (10.1007/s00167-021-06581-0)
• [L5] They can precisely and reproducibly be defined on radiographs. (10.1016/j.arthro.2007.12.012)
• [L4] Posterolateral rim morphology can be delineated on lateral plain film images, with radiographic type 1 rims correlating with distinct anatomic morphology and radiographic type 2 rims correlating with indistinct morphology. (10.1016/j.arthro.2008.04.072)
• [L4] The results suggest that with the proper indications this arthroplasty has a place in reconstructive surgery of the arthritic knee joint. (10.2106/00004623-198567080-00005)
• [L5] The integrity of the Kaplan fibers should be routinely reviewed on MRI scans. (10.1177/0363546520919986)
• [L5] The debate between traditional and innovative alignment techniques is set to continue for some time, and individualisation of knee arthroplasty based on patient anatomy, physiology, and kinematics is the future direction. (10.1302/0301-620x.99b2.38085)
• [L5] The authors argue that successful knee surgery depends on a deep anatomical and functional understanding to restore the patient's individual anatomy, rather than on the surgical technique itself, and caution against assuming newer techniques are superior to older ones without sufficient time to evaluate outcomes. (10.1007/s00167-015-3635-3)
• [L5] Owing to its complexity, CFD is best treated by clinicians with considerable deformity treatment experience to maximize functional outcomes. (10.5435/jaaos-d-21-01186)
• [L5] The surgical technique and indications for this procedure should be investigated further and it is recommended that ALLR be used with caution. (10.1177/2325967116s00166)
• [L4] Failure to treat all injured structures can lead to change in knee kinematics and poorer outcome. (10.1177/2325967120s00519)
• [L3] Selective magnetic resonance imaging does not provide enhanced diagnostic utility over clinical examination, particularly in children, and should be used judiciously in cases where the clinical diagnosis is uncertain and magnetic resonance imaging input will alter the treatment plan. (10.1177/03635465010290030601)
• [L4] CT-based phenotyping established a 3D classification of arthritic knee anatomy into 4 foundational morphologies, of which types 1 and 3 represent outliers present in 26% of knees undergoing TKA. (10.2106/jbjs.24.01466)
• [L5] Isometric grafts restore normal knee kinematics regardless of the flexion angle at which they are secured. (10.1007/s001670050221)
• [L3] Focusing on bone morphology allows surgeons to easily perform visual assessment using preoperative radiographs. (10.1186/s12891-022-05526-z)
• [L5] Conventional non-anatomic ACL reconstruction techniques do not prevent early osteoarthritis nor restore normal dynamic knee function; restoring anatomy may be the key to success, but high-quality prospective randomized trials with precise outcome measures are needed to validate benefits. (10.1007/s00167-010-1222-1)
• [Paper] The advantages of this arthroscopic technique include its minimally invasive nature, the opportunity to perform a diagnostic evaluation, and to treat any concurrent intra-articular pathology. (10.1016/j.eats.2020.03.026)
• [L5] The proposed method can evaluate knee joint mechanical parameters such as stress distribution at the joint contact interface. (10.1007/s00167-010-1190-5)
• [L4] Our series demonstrated satisfactory clinical and functional outcomes. (10.1016/j.arthro.2008.04.048)
• [L5] Biomechanical studies determine the magnitude and direction of forces and moments of various tissues in and around a diarthrodial joint, as well as measure corresponding joint kinematics, to assist clinicians in assessing function and planning treatment. (10.1177/03635465990270042301)
• [L4] Morphologic variations in the tibia and femur influence the kinematics of the knee and contribute to risk of anterior cruciate ligament (ACL) injury as well as function of the knee after injury and after surgical reconstruction. (10.1016/j.csm.2017.07.012)
• [L5] The knee joint simulator successfully demonstrated the anatomy, physiology, and kinematics of knee ligaments, allowed teaching of ligamentous instability tests, and demonstrated the effect of knee ligament reconstructive surgery. (10.1007/s001670050121)
• [L4] MRI is of crucial significance for operative planning and distinguishing benign from malignant soft-tissue tumors. (10.1007/s001670050073)
• [L5] Comprehensive qualitative and quantitative guidelines for assessing posterolateral knee structures on both anteroposterior and lateral knee radiographs were described. (10.1177/0363546508328117)
• [L4] The functional knee phenotype concept better represents the variability of the coronal knee alignment than the conventional system of valgus, varus and neutral. (10.1177/2325967120s00301)
• [Case_report] The authors agree that management should begin with nonoperative treatment, but surgery is indicated when diagnosis is in doubt. (10.1177/03635465000280042501)
• [Paper] Despite progressive radiological grading of OA at long-term follow-up, the functional outcomes seem to be very satisfactory. (10.1007/s00402-019-03150-6)
• [L5] Comparative anatomical studies suggest that understanding these shared kinematic principles can improve the design of external bracing systems and total knee replacements. (10.2106/00004623-198769070-00004)
• [L5] Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up. (10.1186/1749-799x-2-10)
• [L4] MRIs predict ACL length more reliably than radiographs. (10.1016/j.asmr.2019.10.005)
• [L5] These data facilitate repairs and reconstructions that can restore physiological laxity and stability patterns across the arc of knee flexion. (10.1007/s00167-020-06139-6)
• [Case_report] The absence of injury, the mild complaints reported by the patient, his age, skeletal immaturity, and remaining growth led us to adopt a conservative approach to treating this anatomic variant. (10.1186/s12891-021-04696-6)
• [L4] A variety of reliable skeletal maturity estimation systems using routine knee radiographs and MRI are described; orthopaedic surgeons can use these to inform preoperative workups without requiring additional hand radiographs. (10.5435/jaaos-d-24-00133)
• [L4] Surgical release was effective in a case where nonoperative treatment failed. (10.1007/s00167-003-0382-7)
• [L3] It provides satisfactory outcomes without remarkable arthritic changes at a mid term follow-up. (10.1002/ksa.70101)
• [L4] Non-operative management is associated with highly variable periods of convalescence, poor return to preinjury level of function and high risk of injury recurrence. (10.1302/2058-5241.5.200055)
• [L5] More trials and long-term evidence are needed. (10.1136/jisakos-2016-000106)
• [Case_report] Nonoperative treatment may allow the fracture to heal but requires close monitoring of limb vascularisation. (10.1016/j.otsr.2016.07.008)
• [L5] Surgical management is indicated for progressive, painful, unilateral deformity or leg-length discrepancy, while moderate nonprogressive deformity often does not require surgery. (10.5435/00124635-199803000-00003)
• [L4] In patients in whom conservative management fails to ameliorate symptoms, IOBP should be considered. (10.3390/jcm9051358)
• [Case_report] If the patient's symptoms are unresponsive to nonoperative treatment, surgical correction can be effective. (10.1177/03635465010290012101)
• [L5] Most studies have failed to show improved clinical outcomes in the short term when adding cartilage restoration procedures to high tibial osteotomy, raising questions about whether longer term studies will show improved efficacy. (10.1016/j.arthro.2023.07.002)
• [L5] This current concepts review highlights the evaluation and workup of hamstring injuries, nonoperative treatment options, and surgical decision-making based on patient presentation and injury patterns. (10.1177/03635465231164931)
• [L4] The natural course of CECS seems to be persistent symptoms over time. (10.1007/s00167-014-2847-2)
• [L4] The heterogeneity of the pathology treated, follow-up time, and outcome measures limit comparison between studies. (10.1177/2325967116633419)
• [Case_report] The report documents the progression of a purely lytic lesion in Paget's disease of the tibia over twelve years, noting that faster longitudinal growth occurred during the first six years before slowing as the disease extended to involve the entire bone. (10.2106/00004623-197658060-00023)
• [L4] The prognosis after excision is excellent, with no recurrences observed in this series. (10.2106/00004623-196749010-00010)
• [L4] The presence of chondrosis at the time of surgery is an important prognosticator of functional outcome at intermediate follow-up. (10.1177/0363546507311091)
• [L4] At 2-year followup, no clinically significant differences are observed between different CPAK phenotypes. (10.1002/ksa.12099)
• [L4] Although favorable initial evolution at 30 months after a complete ACL lesion, our series show a re-rupture rate or 'scar tissue' rupture of 40% at a mean follow-up of 8 years. (10.1177/2325967118s00188)

See Also

• Anterior Cruciate Ligament
• Biomechanics

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