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Hip instability and microinstability

174 citationsUpdated Oct 2026

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Overview¶

Hip instability and microinstability are frequently associated with femoroacetabular impingement (FAI) morphologic characteristics [1]. The dominant deformity in developmental hip dysplasia is deficient anterolateral acetabular coverage, which results in structural instability and acetabular rim overload [29]. Hips at greatest risk of failure present with advanced arthrosis or a combination of impingement and instability preoperatively [3]. Evaluation of the patient with recurrent hip instability requires a systematic approach involving a thorough history, physical examination, and targeted radiographic evaluation [2]. The long-term prognosis for the symptomatic hip with moderate dysplasia (lateral center-edge angle <15°) treated nonsurgically is very poor [29].

Surgical management ranges from hip arthroscopy to open reconstructive procedures. Hip arthroscopy addresses peripheral compartment pathology, including capsular laxity [23], and is a successful treatment for symptomatic FAI, even in the presence of dysplasia, with a high survivorship rate of 91% at minimum 10-year follow-up [39]. In patients with borderline dysplasia, arthroscopy yields favorable long-term outcomes with low revision rates [17, 20], though indications are narrow and instability-driven symptoms primarily indicate periacetabular osteotomy [74]. For developmental hip dysplasia with deficient acetabular coverage, a reconstructive acetabular osteotomy is the treatment of choice [29], with the Bernese periacetabular osteotomy serving as a mainstay for acetabular reorientation [29]. Concomitant hip arthroscopy and PAO is safe and effective [21], and PAO used as a salvage procedure for instability recalcitrant to prior arthroscopy demonstrates substantial improvement in patient-reported outcome measures and radiographic correction [81].

Headline outcomes indicate that hip arthroscopy for all indications has a complication rate generally less than 1.5% [15]. Routine intraoperative repair of the articular capsule is recommended to positively influence functional results [198], and capsular preservation and closure should remain universal, particularly for patients requiring maximum surgical stability [4]. In patients aged ≥40 years, arthroscopic management of FAI results in significant and durable improvements in pain and function, with conversion to total hip arthroplasty ranging from 2.9% to 13.2% [199]. Primary hip arthroscopy with labral repair in patients 40 years old demonstrates a hip preservation rate of 78% at minimum 10-year follow-up [204]. While additional studies are needed to determine protective factors in patients with abnormal anatomy who do not develop early osteoarthritis [6], current evidence supports ligamentum teres reconstruction predominantly for patients experiencing refractory instability following previous hip preservation procedures [75].

Anatomy & Pathophysiology¶

Bony Anatomy and Morphology¶

The hip is a multiaxial joint formed by the articulation between the pelvis and femur, connecting the axial skeleton and the lower extremity [99]. The hemipelvis comprises the ilium, ischium, and pubis, which unite at the triradiate cartilage within the concave acetabulum [99]. The acetabulum consists of an articular crescent-moon–shaped lunate surface and a nonarticular central fossa that serves as the attachment point for the ligamentum teres [99]. Inferiorly, the acetabulum is incomplete, forming a notch through which vital blood vessels and nerves pass to supply the joint [99]. The femoral head forms two-thirds of a sphere, featuring a small central depression from which the ligamentum teres extends to connect to the acetabular notch [99].

The neck-shaft angle of the femur averages 125°, placing the head and neck more perpendicular to the acetabulum in a neutral position to allow for greater mobility [99]. Normal version, defined as the head-neck angle in the frontal plane, averages 15 to 20° [99]. This angular projection of the femoral head and neck relative to the obliquely placed acetabulum permits rotary movements at the hip and prevents impingement [99]. Acetabular dysplasia is defined by a lateral center-edge angle (LCEA) of <25° on the AP pelvic radiograph, with an LCEA between 20° and 25° considered borderline dysplasia [147]. In dysplasia, the lack of acetabular coverage can lead to excessive femoral head micromotion against the acetabulum, resulting in hip microinstability [147]. This microinstability may cause an overload on acetabular structures, leading to compensatory labral hypertrophy and sometimes rim fractures [147]. A lower center-edge angle or larger Tönnis angle increases the risk for severe cartilage damage to the femoral head; specifically, patients with a lateral center-edge angle of 25° were 3.57 times more likely to have severe cartilage damage to the femoral head [147].

Femoroacetabular impingement (FAI) involves specific morphologic deformities. Cam impingement refers to femoral-based deformities, such as an aspherical femoral head or reduced head-neck offset, that result in repetitive abutment of the acetabular rim and femoral head-neck junction [9]. Pincer impingement describes acetabular-based deformities, such as acetabular retroversion or acetabular protrusio, that create abnormal abutment of the acetabular rim and femoral head-neck junction [9]. Combined cam/pincer deformities are common in femoroacetabular impingement [24]. High rates of FAI morphologic characteristics are present in patients with hip instability [1]. Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness [5]. Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions [63]. Increased cam morphology remained a significant contributor to reduced internal rotation but did not affect hip flexion [130]. Hip impingement in patients with FAIS may routinely occur at hip flexion angles below 90° in neutral rotation, with males engaging at higher flexion angles than females [163]. Age-related differences exist in the morphology and kinematics of the native hip, specifically regarding the position of the femoral head within the acetabulum [95].

Soft Tissue Anatomy and Biomechanics¶

The acetabular labrum is a triangular fibrocartilaginous ring attached firmly to the acetabular rim, encompassing nearly the entire acetabulum except for the most inferior aspect bridged by the transverse acetabular ligament [59]. The labrum deepens the acetabulum, increases coverage of the femoral head, and plays a role in shock absorption, joint lubrication, and pressure distribution [59]. Its most critical role is the creation of a negative pressure seal with the femoral head, which aids in joint stability [59]. Removal of the labrum leads to a shift in the femoral contact point toward the acetabular rim, a decrease in intra-articular fluid pressurization, and a loss of lateral restraint to femoral head motion [59]. Labral removal has been shown to increase contact stresses between the articular cartilage of the femoral head and the acetabulum by 92% [59]. Only the external one-third of the labrum contains blood vessels, leaving the majority of the structure avascular and limiting its healing ability following injury [99]. The labrum is highly innervated, with the presence of both mechanoreceptors and nociceptors [99].

The hip is surrounded by a dense fibrous capsule extending from the periphery of the acetabulum to the intertrochanteric line of the femoral neck [99]. The capsule enhances joint stability by preventing translation of the femoral head in the acetabulum [99]. The hip joint capsule extends anteriorly to the intertrochanteric crest but posteriorly only partially across the femoral neck, leaving the basicervical and intertrochanteric crest regions extracapsular [96]. The capsule is tight in extension and internal rotation, and relaxed in flexion and external rotation [96]. Three main ligaments support the hip: * Iliofemoral ligament: The thickest and strongest of the three main ligaments, originating at the AIIS and inserting at the intertrochanteric line [99]. It functions to limit external rotation, while its lateral arm limits extension of the joint [99]. It becomes taut in full extension, preventing anterior dislocation and hyperextension of the hip [100]. * Ischiofemoral ligament: Extends from the ischial margin of the acetabulum to the greater trochanter of the femur, providing support posteriorly and restricting internal rotation motion [99]. It reinforces the posterior capsule and provides a check to internal rotation of the hip [100]. * Pubofemoral ligament: Extends from the obturator crest of the pubic bone to the femoral neck and acts to limit abduction of the joint [99]. It attaches to the inferior and medial part of the capsule and may cause a hip adduction contracture [100].

Deep fibers from the iliofemoral, ischiofemoral, and pubofemoral ligaments merge to form the zona orbicularis, which circumvents the femoral neck [99]. The twisted orientation of the hip ligaments provides a screw mechanism for the hip in full extension [100]. The ligamentum teres originates in the cotyloid fossa and attaches on the fovea of the femoral head [100]. It transmits an arterial branch of the posterior division of the obturator artery to the femoral head, which is less significant in adults [96]. The ligamentum teres appears to play a secondary role to other soft-tissue restraints, having been shown to restrict the motion of the femoral head [182]. Isolated tears of the ligamentum teres have been found in hip dysplasia, where it may play a more prominent role in stabilization [182].

The average range of motion of a normal hip is approximately 120° of flexion, 30° of extension, 45° of abduction, 20° to 30° of adduction, 35° of internal rotation, and 45° of external rotation [103]. Normal gait function requires hip flexion of 30°, hyperextension of 10°, abduction and adduction of 5°, and internal and external rotation of 5° [103]. The primary hip flexor muscles are the iliopsoas, rectus femoris, and sartorius muscles [103]. The gluteus medius and minimus muscles function together to maintain and abduct the femur during the stance phase of gait [103]. The external rotators of the hip include the obturator internus and externus, superior and inferior gemelli, quadratus femoris, and piriformis muscles [103]. The most consistent internal rotators of the hip joint are the gluteus medius and tensor fascia latae muscles [103].

Pathophysiology of Instability and Microinstability¶

Hip microinstability refers to the femoral head micromotion within the acetabulum, which is a prolonged phenomenon that leads to cartilage damage and eventually osteoarthritis of the hip [44]. The definition of microinstability remains controversial, but recent studies describe it as an abnormal femoral head micromotion within the acetabulum with a negative effect on the articular cartilage [51]. Hip microinstability is characterized by a progressive onset with pain, disability, and a feeling of giving way in the hip [51]. Motion of the femur relative to the acetabulum is the result of the absolute biomechanical force acting on the hip joint, which is affected by numerous factors including the bones (acetabulum, femur) and soft tissues (labrum, capsule, ligamentum teres, muscles) [44].

Both bony and soft-tissue dearrangements of the hip joint and/or the surrounding tissues have been associated with hip microinstability [147]. The major stabilizers in the hip are the static restraints, which include both osseous and soft-tissue structures [182]. The degree of acetabular coverage and the femoral and acetabular version are key determinants of stability [182]. In the setting of diminished acetabular coverage and alterations in normal version, the hip joint increasingly relies on soft-tissue structures to maintain stability [182]. In the setting of hip dysplasia, the individual is much more reliant on soft-tissue structures to stabilize the hip [182]. Hip microinstability can occur in athletes with mild osseous hip dysplasia superimposed on ligamentous laxity during sports requiring high degrees of hip motion [182].

Femoroacetabular impingement can contribute to the development of hip microinstability due to the altered relationship between the femoral head and acetabulum [147]. Pincer and/or cam impingement with or without additional morphologic alteration can lead to levering of the femoral head posteriorly, resulting in hip microinstability and, in extreme cases, posterior hip dislocation [147]. A sequela of a large cam-based deformity in FAI is impingement of the cam lesion inside the acetabulum in flexion, which levers the femoral head posteriorly and can cause a posterior contrecoup cartilage lesion, with posterior subluxation and instability [182]. FAI-related damage to the labrum and loss of the seal between the labrum and the femoral head might generate microinstability pathology [51]. In patients without dysplasia, chondral damage may be due to excess abnormal femoral micromotion, leading to uneven loading of the chondral surfaces in the hip joint [147].

Damage to the hip capsule may cause instability of the hip; however, loss of the seal between the labrum and the femoral head may cause increased movement of the femoral head or microinstability [51]. Current evidence supports that the hip capsule is the structure that is mainly implicated in hip microinstability [51]. Capsular stretching can be the result of inherent tissue laxity or anatomic stretching due to pathologic motion of its bony attachment sites on the femoral bone and the acetabular rim, such as in hips with FAI or dysplasia [179]. The capsulotomy performed during hip arthroscopy disrupts the fibers of the iliofemoral ligament [179]. The iliofemoral ligament has been reported to resist external rotation in hip flexion and both external and internal rotation in hip extension [179]. The pubofemoral ligament resists external rotation in extension or abduction, and the ischiofemoral ligament resists internal rotation in flexion or extension [179]. Damage to any aspect of the capsular complex may result in increased microinstability [179]. Capsular laxity leads to microinstability, demonstrated by a significant increase in femoral head translation when incisions are made in the capsule complex [179]. Stretching of the capsule may contribute to microinstability, with a significant increase in femoral head displacement following cyclical stretching of the capsule [179].

Sports with repetitive torsional movements can produce soft-tissue attenuation because of repetitive microtrauma to the capsule and ligaments [182]. Atraumatic origins of hip instability can be seen in patients with congenital soft-tissue deficiency or laxity, such as the capsular and ligamentous laxity seen in Ehlers-Danlos syndrome, Marfan syndrome, and Down syndrome [182]. Hip instability has been increasingly recognized as a pathologic entity and a source of chronic pain and disability over the past decade, especially in cases of more subtle atraumatic instability [182]. Athletes with hip microinstability may report mechanical symptoms and feelings of instability, especially in hip positions that rely more on soft-tissue restraint such as hip extension and external rotation [182]. Secondary iliopsoas tendinitis from strain on the iliopsoas as it attempts to stabilize the anterior hip joint can develop in patients with hip microinstability [182]. The log-roll external rotation test may show capsular laxity, with diminished spring back during external rotation [182].

The diagnosis of microinstability without the presence of bony abnormality is described as difficult because signs and symptoms may be subtle, and there is no definitive preoperative diagnostic test, examination finding, or imaging modality that is pathognomic for hip microinstability [26]. Hip microinstability is not well defined, and patients commonly present with pain with progressive onset [44]. There has been significant growth in evidence to support hip microinstability as a real entity, even without the presence of bony deficiency [26].

Management of microinstability may start with physical therapy, and if improvement is not seen, hip arthroscopy may include thermal capsulorrhaphy or plication with absorbable sutures and reestablishment of the seal between the labrum and the femoral head [51]. Hip arthroscopy can be used to treat microinstability by reestablishing the labral-femoral head seal and addressing any capsular looseness or damage [51]. Biomechanical evidence supports closure of the capsule after hip arthroscopy to reverse the significant effects of capsulotomy [135]. The puncture capsulotomy technique preserves the native anatomy and biomechanics of the hip joint by leaving the iliofemoral ligament intact, thereby eliminating the risk of gross anterior dislocation and avoiding postoperative range-of-motion restrictions associated with traditional capsulotomy [145]. The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip [8].

Following a diagnosis of hypermobility/microinstability or structural instability of the hip joint, patient education and counseling regarding activity modification is of primary concern to protect and/or avoid further injury in the region [26]. Nonsurgical management of individuals with hip hypermobility/microinstability should focus on the strengthening of periarticular musculature, particularly the iliopsoas, gluteals, adductors, and rotators, in addition to the core musculature [26]. Strength of the abductor and external rotator groups is of particular importance in controlling lower extremity alignment during functional activities [26]. Individuals with excessive hip external rotation ROM have decreased strength of the hip internal rotators, and those with excessive internal rotation ROM have decreased strength of the hip external rotators [26]. The development and maintenance of sufficient strength to limit and/or control excessive hip ROM is essential in the nonsurgical management of this population [26]. In the presence of joint hypermobility, neuromuscular reeducation including proprioceptive and perturbation training may be beneficial [26]. Individuals with labral pathology and compromised hip stability may benefit from the inclusion of dynamic stabilization and/or perturbation training to increase the efficiency of the surrounding musculature [26]. Lumbopelvic stability and restoring appropriate hip biomechanics and muscle firing patterns are key to successful return to activity and sport [137].

Hip-combined rotational morphology has little short-term impact on clinical outcomes after hip arthroscopy in FAIS patients [31]. Hip arthroscopic surgery yields meaningful improvements in hip function in the majority of patients, regardless of sex [172]. Gait analysis of FAIS patients after hip arthroscopy demonstrated small, albeit significant, changes in postoperative hip kinetics and kinematics; however, these changes did not correlate with the large, clinically significant improvements in PROs at 1 year after surgery [150]. Patients reported significant improvement in function and pain at 1 year postoperatively after arthroscopy for

Classification¶

Clinical Definitions and Diagnostic Criteria¶

FAI syndrome is defined as a motion-related clinical disorder of the hip characterized by a triad of symptoms, clinical signs, and imaging findings [49]. The diagnosis of pincer- and cam-type FAI relies on history, positive impingement signs on examination, and radiographic evidence for pincer-type FAI [231]. Inclusion criteria for FAIS diagnosis in the HAFAI cohort required an α angle ≥ 55° on an anteroposterior standing pelvis radiograph or axial view for cam impingement, and a lateral centre edge angle > 25° on an AP radiograph for pincer impingement [251]. The exact definition of 'impingement' eludes the current literature; while dynamic MRI has potential to better define hip impingement, it is not yet optimized for widespread clinical use [89].

Radiographic and Morphologic Classification¶

An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability [61]. For determining the presence of a crossover sign, advanced 3D CT-generated hip models improve inter- and intra-observer agreement compared to plain radiographs [34]. Unstable hips demonstrated a more recessed acetabular dome when compared to stable hips [248]. Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of PAO by giving a better understanding of the 3-dimensional deformity [222].

Soft Tissue and Chondrolabral Classification¶

Acetabular labral tears are significantly associated with structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs [11]. The acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability [87]. Understanding of hip disorder-specific chondral damage patterns may be useful for the development of arthroscopic classification of hip disorders and may lead to the establishment of treatment guidelines [178]. The New Bern Chondrolabral Classification was developed to address inadequate reliability and incomplete characterization of lesions in existing systems for early chondrolabral degeneration in young adults with hip pain [229]. In joint-preserving hip surgery, lesions of the ligamentous-fossa-foveolar complex (LFFC) are very common, with 65% of hips showing substantial damage [241].

Labral Tear Grading: Acetabular labrum tears were categorized into 5 grades from mild to severe: (1) no lesions, (2) partial tear, (3) full tear, (4) intrasubstance tear, and (5) hypoplastic labrum [208]. A partial tear is defined as a hyperintense signal extending between the labral base and acetabular rim [208]. A full tear is defined as complete interposition of a hyperintense signal between the labral base and acetabular rim [208]. An intrasubstance tear is defined as a focal, hyperintense signal extending into the labral surface [208]. Hypoplastic labrum is used to describe a nearly absent labrum [208].

Chondrolabral Junction Grading: The Beck classification of transition zone cartilage was used to grade chondrolabral junction (CLJ) damage, with grades 0 to 2 stratified into the mild CLJ damage cohort and grades 3 and 4 stratified into the severe CLJ damage cohort [242].

Evaluation and Imaging Protocols¶

A thorough evaluation of the hip must include a comprehensive medical and surgical history focused on the hip joint, surrounding soft tissues, and associated structures, followed by a physical examination in multiple positions and gait assessment to distinguish between intra-articular and extra-articular contributors to hip pain [13]. A comprehensive approach to interpretation of magnetic resonance examination of the hip includes optimal sequences and planes for identifying key pathology and quantifying bony morphology [10].

QUADAS Tool: The QUADAS tool consists of 14 items that can be scored yes, no, or unclear for the quality assessment of diagnostic accuracy studies [41]. In the QUADAS assessment, if half of the items or fewer scored yes, a study was graded “poor,” and studies that scored yes for three-fourths of items or more were graded “good” [41].

Microinstability and Phenotypic Considerations¶

Hip microinstability is a newly defined hip pathology in young athletes [25]. Management of hip microinstability focuses on strengthening the dynamic stabilizers of the hip through focused physical therapy [25]. Hip capsular preservation and closure should remain universal, particularly for patients with specific phenotypes requiring maximum surgical stability [4]. Patients with borderline hip dysplasia and radiographic evidence of hip instability, as measured by the FEAR index (≥2), may achieve similar improvement in 2-year outcomes compared to those with radiographically stable hips after arthroscopic treatment of FAIS [245]. Concomitant procedures represent a powerful solution for the treatment of severe hip dysplasia and intra-articular pathologies resulting from instability or combined FAIS [88].

Clinical Presentation¶

History and Symptoms¶

Symptomatic femoroacetabular impingement (FAI) typically presents with activity-related groin pain exacerbated by hip flexion, such as prolonged sitting [24, 50]. Patients frequently report difficulty with walking, running, or pivoting, and the onset is often insidious or follows minor trauma [24]. Mechanical symptoms secondary to labral and articular cartilage disease are common [24]. Pain may radiate laterally toward the trochanteric region, medially into the adductor region, and rarely into the buttocks or down to the knee [50]. Acetabular labral disease similarly presents with groin pain worsened by prolonged sitting, walking, running, or pivoting [9].

Hip microinstability is characterized by anterior hip pain accompanied by a sense of the joint giving way or dislocating during activity [45, 54]. This condition is often seen in athletes requiring extreme range of motion, such as dancers, or those participating in sports involving hyperextension [44, 54]. Patients often describe hip or groin pain that has increased over time [54]. Hip dysplasia may present with lateral hip pain attributed to decreased abductor strength, which is often the initial symptom and worsens later in the day as fatigue develops [138]. Deep anterior groin pain in dysplasia indicates joint-originating pain from overload, edge-loading, or labral injury, and is activity-related, improving with restriction [138]. Hip instability may also present with pain of progressive onset [44]. Notably, a clinical diagnosis of hip osteoarthritis was found in approximately 22% of young patients undergoing hip arthroscopy within 2 years [53].

Physical Examination¶

A thorough hip evaluation requires a comprehensive medical and surgical history focused on the joint, surrounding soft tissues, and associated structures [13]. Physical examination should be performed in multiple positions and include gait assessment to distinguish intra-articular from extra-articular pain contributors [13]. In FAI, restricted hip internal rotation in 90° of flexion is characteristic [24]. The impingement test (flexion, adduction, internal rotation) elicits pain but is not specific for FAI [24]. Hip strength deficits are common in unilateral symptomatic FAI, occurring most frequently in abduction and flexion [139]. Excessive hip external rotation range of motion is associated with decreased internal rotator strength, while excessive internal rotation range of motion is associated with decreased external rotator strength [26]. Pathologic thickening of the hip capsule may contribute to restricted mobility [65].

For hip microinstability, examination focuses on stressing the anterior or posterior capsule to reproduce symptoms [45]. The abduction-hyperextension-external rotation test, prone instability test, and hyperextension-external rotation test aid in diagnosis [45]. Patients often present with a positive anterior impingement sign and/or a positive labral stress test [45]. There is no definitive preoperative diagnostic test, examination finding, or imaging modality pathognomic for hip microinstability [26]. Diagnosis without bony abnormality is difficult due to subtle signs and symptoms [26]. The clinical impingement sign is challenged as a specific diagnostic test for hip pathology in athletes [129]. Until radiologic criteria are confirmed, surgeons must rely on expert clinical examination, as sensitivity, specificity, and observer consistency for radiographic FAI diagnosis require confirmation [72].

In infants with developmental dysplasia of the hip (DDH), the patient must be relaxed, warm, and well fed [55]. A decrease in abduction is the most sensitive test result [55]. The Galeazzi test is positive when the knee on the involved side is lower than the contralateral knee in unilateral subluxation or dislocation [55]. The Barlow test is positive when the affected hip subluxates or dislocates, and the Ortolani test is positive when a dislocated hip is reducible, often with a palpable clunk [55]. Asymmetric skin folds and hip clicks are unreliable and nonspecific findings [55]. In toddlers, restricted motion may accompany limb-length discrepancy, limp, or waddling gait; bilateral dislocations often present with lumbar hyperlordosis [55]. Adolescents may manifest fatigue and pain in the hip, thigh, or knee [55].

Ligamentum teres tears require a high degree of suspicion for clinical diagnosis, with preoperative diagnosis rates as low as 4% or 5% [117]. Specific physical tests for these tears have sensitivity and specificity values of 90% and 85%, respectively [117].

Imaging and Diagnostic Findings¶

Radiographic evidence of FAI is common in active patients with hip complaints [57]. The overall prevalence of radiographic findings consistent with FAI in young patients with hip pain was 60.5% [62]. A significant association exists between acetabular labral tears and structural abnormalities, with 87% of patients having at least one abnormality detectable on conventional radiographs [11]. Acetabular and femoral osseous abnormalities are commonly associated with labral tears [170].

Imaging Modalities: * AP Pelvis View: Assesses acetabular anatomy, including version, coverage, and femoral head sphericity [24]. * Lateral Views: The 45° Dunn view and frog-leg lateral assess femoral head sphericity and head-neck offset [24]. * MRI/MRA: Provides information on labral and cartilage integrity, proximal femur anatomy, and acetabular/femoral version; however, sensitivity to acetabular rim chondral lesions is limited [24]. * Low-dose CT: With three-dimensional reformats, is particularly useful for surgical planning of complex or borderline deformities [24].

An isolated assessment of the lateral center-edge angle (LCEA) is an oversimplistic approach that may jeopardize appropriate classification and provide insufficient data for hips with additional features of dysplasia and instability [61]. The presence of apparently abnormal imaging findings in asymptomatic patients is well-known, with a 21% risk of developing symptoms from labral tears [67]. Approximately one in four patients with FAI presents with symptoms in the contralateral hip, and 16% of initially asymptomatic contralateral hips will develop symptoms during the next several years [69]. The prevalence of radiographic hip findings reminiscent of FAI is high in asymptomatic Asian populations [165].

Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes in FAI studies, while measures of hip strength and range of motion are underreported [7]. Current surgical outcomes for FAI are limited to mid-term follow-up time frames with inconsistent reporting [7]. Due to a high percentage of overlapping questions between commonly used hip-specific patient-reported outcome measures, multiple tests may be appropriate for use [28].

The "windshield wiper sign," an osteochondral defect of the anterolateral femoral head, predicts instability and allows planning of combined arthroscopic cartilage therapy and periacetabular osteotomy [48]. Decreased hip ligament thickness in patients with dysplasia may contribute to hip instability above and beyond associated acetabular under-coverage [5]. Both acetabular and femoral morphology are critical to understanding FAI and developing patient-specific treatments, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions [63].

The Warwick Agreement defines FAI syndrome as a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs, and imaging findings [49]. The definition includes five essential elements: abnormal morphology of the femur and/or acetabulum, abnormal contact between these structures, vigorous supraphysiologic motion resulting in abnormal contact, repetitive motion resulting in continuous insult, and the presence of soft-tissue damage [50]. The presence of FAI morphology does not necessarily mean FAI is the primary source of hip pain; other less common causes, such as osteoid osteoma, should be included in the differential diagnosis when atypical clinical and radiological signs are found [151]. Extraarticular FAI is an uncommon source of impingement symptoms, often missed due to prior hip surgery, and seems more common in younger, female patients [169].

The incidence of labral pathology in patients with hip dysplasia is reported to occur in two-thirds of patients [138]. The incidence of labral pathology in asymptomatic young adults is approximately 40% [138]. Acetabular cartilage lesions are present in 69% of adult hip dysplasia cases, and combined labral/cartilage lesions are present in 59%, most commonly seen on the anterior and superolateral acetabulum [138]. A 93% incidence of labral tears has been reported in patients with persistent pain or mechanical symptoms after hip dislocation with negative plain radiographs or computed tomography [177]. Magnetic resonance imaging or arthrography has shown an accuracy of 91% in detecting pathology in patients with persistent pain after hip dislocation, though 15% of patients had loose bodies not detected on imaging [177]. Arthroscopy is indicated as a diagnostic tool when imaging is equivocal for hip dislocation complications [177].

The Beighton score and additional radiographic factors suggestive of instability should be evaluated in patients with combined borderline hip dysplasia and excessive femoral anteversion, as these findings may portend inferior outcomes after arthroscopic treatment in isolation [168]. Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes [148]. Future studies should develop an algorithm combining symptoms, clinical examination, and radiological signs to determine whether borderline dysplastic hips require arthroscopy or bony correction [164].

Investigations¶

Clinical Evaluation and History: A thorough history is essential to differentiate between common causes of hip pain, with clinical examination tests and imaging findings used to confirm a suspected diagnosis [22]. Evaluation of the patient with recurrent hip instability should be approached systematically with a thorough history and physical examination [2]. Patients with symptomatic femoroacetabular impingement (FAI) frequently present with activity-related groin pain exacerbated by hip flexion activities [24]. These patients frequently report difficulty with prolonged sitting, walking, running, or pivoting [24]. The onset of symptoms in symptomatic FAI is often insidious or follows minor trauma [24]. Mechanical symptoms secondary to labral and articular cartilage disease are frequently reported by patients with symptomatic FAI [24]. The impingement test (flexion, adduction, internal rotation) elicits pain in patients with FAI but is not specific for the condition [24].

Plain radiography: Conventional radiographs remain critical in the initial imaging evaluation of the hip [43]. A complete hip series usually consists of an anterior-posterior (AP) pelvis, a centered AP hip, a lateral view (frog-leg, cross-table, Dunn 45° or 90°), and a false-profile (Lequesne) view [43]. Various lateral views, most commonly the 45° Dunn view and frog-leg lateral, are used to assess femoral head sphericity and head-neck offset [24]. The femoral head-neck junction morphology is often assessed using the alpha angle [43]. Some studies have shown that radiographs, in particular the Dunn 45° view, may be more accurate for determining the alpha angle measurement than CT or MRI [43]. The "crossover" sign on an AP pelvis radiograph indicates acetabular retroversion related to lateralization of the anterior acetabular wall relative to the posterior acetabular wall [43]. Pelvic tilt or rotation may lead to false-positive and false-negative "crossover" signs on AP pelvis radiographs [43]. For neutral pelvic tilt, the sacrococcygeal joint should be between 3 and 5 cm above the superior border of the symphysis pubis [43]. The Tönnis angle is defined by the angle of the acetabular sourcil and a line parallel to the transverse pelvis axis, with values between 0° and 10° considered normal [43]. The lateral center-edge angle of Wiberg is the angle between a line from the center of the femoral head perpendicular to the transverse pelvis axis and a second line from the center of the femoral head to the superolateral most point of the acetabulum [43]. Center-edge angles of 20°–40° are considered normal, while angles from 20° to 25° are considered borderline [43]. The femoral head extrusion index is defined by the length of the femoral head that lies beyond the acetabulum as a percentage of the total horizontal width of the femoral head, with values greater than 25% considered abnormal [43]. Coxa profunda is diagnosed when the fossa line touches or is medial to the ilioischial line on an AP pelvis radiograph [43].

MRI: The anatomy of the proximal femur as well as the version of the acetabulum and femur may be assessed using MRI or magnetic resonance arthrography [24]. Sensitivity to acetabular rim chondral lesions is limited in MRI or magnetic resonance arthrography [24]. For patients suspected of soft tissue or intra-articular pathology, MRI is the modality of choice, given its superior sensitivity and specificity [111]. Conventional MRI is effective at identifying osteochondral injuries, musculotendinous pathologies, and inflammation [111]. Magnetic resonance arthrography (MRA) is more appropriate to determine injuries to the labrochondral structures and the ligamentum teres and identify the presence of loose bodies and synovial chondromatosis [111]. In the accurate detection and staging of articular cartilage lesions, the utility of MRA is reduced, with sensitivity reported to be less than 50% compared with arthroscopic findings [111]. Recent advances in MRI imaging techniques, such as delayed gadolinium-enhanced MR imaging and T2 mapping, allow for a more in-depth analysis of the structure of articular cartilage [111]. Delayed gadolinium-enhanced MR imaging and T2 mapping were effective at detecting early changes to the articular cartilage surfaces of patients with hip dysplasia and femoroacetabular impingement [111]. Noncontrast MRI at 3T is generally adequate for diagnosing intra-articular pathology [119]. If 3T imaging is unavailable, MRA can be considered at 1.5T for increased diagnostic accuracy [119]. MRI is also helpful in identifying femoral neck stress fracture in athletes and predicting patients that may require surgical intervention [119]. This article describes a comprehensive approach to interpretation of magnetic resonance examination of the hip, including optimal sequences and planes for identifying key pathology and quantifying bony morphology [10]. In patients with FAIS, both MRI and MRA have excellent reliability for quantifying hip capsular thickness [244]. Significant agreement of angular measurements for hip morphology exists between Zero Echo Time (ZTE) MRI and CT imaging [254]. Preoperative MRI did not alter indications for primary hip arthroscopy in patients aged 40 years and younger with a history, physical examination findings, and radiographs concordant with FAIS [227]. Preoperative MRI for patients with FAIS aged 40 or under undergoing primary hip arthroscopy provides little to no actionable clinical information with respect to the labrum or cartilage and may negatively impact outcomes by delaying access to care unnecessarily by at least two weeks [265]. MRI is useful to diagnose or rule out non-FAI pathology, ascertain labral pathology, and outline hip alignment [239]. Clinicians must 'treat the patient, not the MRI' regarding dynamic MRI for impingement [89].

CT: CT scans are effective for examining cortical and cancellous bone and can be used to create three-dimensional reconstructions of the hip for use in surgical planning [111]. Measurements of femoral head coverage and acetabular and femoral impingement can also be performed reliably using CT images [111]. The multiplanar and 3D capabilities of CT make it an invaluable tool for assessing bone morphology, but at higher cost and radiation dose [119]. 3D volume renderings are useful to aid in preoperative planning in FAI and subspine impingement [119]. For determining the presence of a crossover sign, advanced 3D CT-generated hip models improve inter- and intra-observer agreement [34]. Plain radiographs are key in the initial assessment of patients suspected of femoroacetabular impingement, while computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy [237]. Multidirectional CT arthrography demonstrated promising diagnostic strength for hip lesions such as labral tears and chondral defects [246].

Ultrasonography: Ultrasonography provides real-time dynamic assessment of the hip and is useful in diagnosing soft-tissue abnormalities about the hip joint [101]. Ultrasonography is particularly useful in providing real-time guidance during diagnostic and therapeutic procedures [101]. Although ultrasonography is a valuable tool to examine pediatric hip conditions, its utility in evaluating the adult hip is limited [111]. Ultrasonography can be an effective modality to identify musculotendinous disruptions, effusions associated with intra-articular pathology, or inflammatory conditions, such as bursitis [111]. Ultrasonography is also being increasingly used for targeted injections into muscles, tendons, or intra-articularly around the hip [111]. Ultrasonography allows bedside evaluation of the hip and can be used to guide interventions in the office setting [119].

Other Considerations: Radiographic indicators of FAI are very common among athletes evaluated at the National Football League Scouting Combine subjected to radiographic examination for the clinical suspicion of hip disease [263]. Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in Japanese patients with hip pain, with cam deformity findings being the most common [252]. A narrow posterior joint space on a False Profile radiograph does not correlate with posterior joint cartilage degeneration in hip preservation patients [255]. Sensitivity, specificity, and intraobserver and interobserver observational consistency for femoroacetabular impingement radiographic diagnosis require confirmation [72]. Until radiologic criteria are confirmed, hip arthroscopic surgeons must rely on expert clinical examination [72]. A computer-assisted analysis of young adult hip radiographs generally demonstrates substantial to excellent levels of interobserver reliability for most parameters [234]. Surgeons experienced in FAI/Dysplasia have higher interrater agreement in making a diagnosis of such hip disorders than other hip surgeons, however, this remains only fair when based on x-rays and moderate when other imaging is included [264]. The study showed a significant association between acetabular labral tears and structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs [11]. Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability [87]. Small changes in acetabular rim morphology on the order of 0.5 mm may be the difference between symptomatic FAIS and the unaffected hip [257]. The presence of apparently abnormal imaging findings in asymptomatic patients is well-known, and while preventive treatment cannot be justified for labral tears in the hip, patients should be informed that there is a 21% risk of developing symptoms [67]. Most patients with unilateral symptomatic FAI and radiographic diagnosis of bilateral FAI became symptomatic relatively quickly and most of them underwent subsequent surgical intervention in the contralateral hip [253]. Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes, while measures of hip strength and range of motion are underreported [7]. As there is a high percentage of overlapping (identical or similar) questions between the most commonly used hip-specific PROs for FAIS, multiple tests may be appropriate for use [28].

Treatment¶

Non-Operative¶

Physical therapy serves as the first-line treatment for hip microinstability, prioritizing the strengthening of dynamic stabilizers [25]. Nonsurgical management of hip hypermobility or microinstability targets periarticular musculature, specifically the iliopsoas, gluteals, adductors, rotators, and core [26]. Strength in the abductor and external rotator groups is particularly important for controlling lower extremity alignment during functional activities [26]. Neuromuscular reeducation, including proprioceptive and perturbation training, may benefit individuals with joint hypermobility [26]. Flexibility exercises are prescribed with caution only after end-feels have been assessed and are discouraged in patients with excessive range of motion [26]. For hip dysplasia, a trial of conservative management involving anti-inflammatory medications, activity modification, physical therapy, and intra-articular injections should precede surgical consideration [142]. Nonoperative treatment remains the first line for most femoroacetabular impingement (FAI) patients and should not be abandoned for early surgery [215]. Hip arthroscopy is appropriate only after failure to improve following a full course of physical therapy [215]. A four-stage conservative program involving anti-inflammatories, rest, guided stretching, and avoidance of provocative hip motions led to significantly improved patient-reported outcomes in a small cohort [190]. There is no agreed-upon conservative care treatment protocol for FAI [190]. Hyaluronic acid injections appear to confer reliable short-term improvements in hip pain and function for symptomatic FAI, but potential intermediate-term and long-term benefit has not yet been demonstrated [202]. Hip-related quality of life improved by clinically meaningful amounts in both surgical and non-surgical groups in a randomized controlled trial comparing arthroscopy to physical therapy [192]. In a meta-analysis, hip arthroscopy was statistically superior to conservative treatment in both long-term and short-term effects [228]. No evidence exists on outcomes following non-operative management of FAI with concomitant Tönnis Grade 2 or more osteoarthritis of the hip [216]. Patients with FAI syndrome and concomitant hip osteoarthritis of Tönnis grade 2 or greater benefit from operative management rather than nonoperative management if they are younger and/or have a normal body mass index [191]. Patients with FAI syndrome and concomitant hip osteoarthritis of Tönnis grade 3 are poor candidates for hip preservation surgery [191]. The indication for surgery should be established cautiously when degenerative changes are present [185]. Careful evaluation of symptoms, hip disease, and expectations is needed before proceeding with surgery in patients at least 50 years of age [38]. Age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair [193]. When surgery is indicated, age 40 years should not be considered an independent contraindication to arthroscopic acetabular labral repair [171]. Prehabilitation intervention development for FAI syndrome is being defined using the Medical Research Council framework, informed by systematic reviews and international expert consensus [184]. Targeted rehabilitation for FAI should integrate hip-centric and core stabilization exercises, though longitudinal studies are needed to validate therapeutic efficacy [213].

Operative¶

Indications: Hip arthroscopy is a safe procedure with a reported complication frequency generally less than 1.5% for all indications [15]. Early functional improvements after hip arthroscopy, assessed by 6-month minimal clinically important difference, predicted clinically meaningful outcomes at 5-year follow-up [77]. Hip arthroscopy for FAI in patients aged less than 50 demonstrates favorable and safe mid-term outcomes [205]. Hip arthroscopy for FAI shows persistent clinical improvement in the mid-term [185]. Both hip arthroscopy and open surgical hip dislocation showed excellent and equivalent hip survival rates at medium-term follow-up [80]. Hip arthroscopy for FAI in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups [226]. In a small sample, simultaneous bilateral hip arthroscopy is safe and effective, resulting in similar improvements in patient-reported outcomes at 1-year follow-up compared with staged bilateral procedures [200]. Hip arthroscopy can be cost-effective given a long enough duration of benefit and appropriate patient selection [73]. A positive response to preoperative intra-articular anesthetic injection suggests favorable outcomes after hip arthroscopy in patients with FAI syndrome [212]. There are both modifiable and non-modifiable pre-operative factors that have the potential to predict a return to high functional status after hip arthroscopy for FAI [206]. There is a severe lack of evidence on the athlete characteristics and clinical course of nonreturning athletes after hip arthroscopy for FAI syndrome [35]. The leading cause of failure after hip arthroscopy is inadequate bony resection of cam (majority) or pincer deformities [142]. Excessive resection has recently been proposed as a potential reason for failure after hip arthroscopy [142]. Iatrogenic chondrolabral injury is the most reported complication in hip arthroscopy [23]. Neurapraxia is a common but transient complication following hip arthroscopy, with an incidence approaching 50% in one series [23]. Permanent nerve injury following hip arthroscopy is less than 5% [23]. Inadequate resection in FAI surgery, more commonly on the femoral side, is the most common reason for revision hip preservation surgery [23]. Hip arthroscopy for symptomatic FAI is a successful treatment in cases where dysplasia is present, demonstrating low complication rates, comparable outcomes to nondysplastic cases, and a high survivorship rate of 91% at minimum 10-year follow-up [39]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy for FAI syndrome with minimum 10-year follow-up [40]. Hip arthroscopy for borderline hip dysplasia has a role with narrow indications, particularly in revision settings where the root cause of failure must be identified [74]. Instability-driven symptoms in borderline dysplasia primarily indicate periacetabular osteotomy rather than arthroscopy [74]. Arthroscopic treatment of mild hip dysplasia can result in excellent outcome and avoid more invasive periacetabular osteotomy [88]. Concomitant procedures represent a powerful solution for the treatment of severe hip dysplasia and intra-articular pathologies resulting from instability or combined FAI syndrome [88].

Surgical Approach / Technique: During hip arthroscopy for microinstability, it is important to determine whether the labral-femoral head seal is reestablished following labral repair by visualization on dynamic examination [159]. If the hip capsule is felt to be loose during arthroscopic examination with a probe, thermal capsulorrhaphy may help shrink the redundancy or absorbable sutures may be used to plicate the capsule [159]. A capsulotomy performed during hip arthroscopy can cause damage to the iliofemoral ligament [159]. At least 50% of the iliofemoral ligament is damaged when performing a subspine trimming using a transverse interportal capsulotomy [159]. Care should be taken when performing an intraportal capsulotomy to preserve as much of the iliofemoral ligament as possible [159]. Following completion of hip arthroscopy, the capsule should be repaired to avoid any instability due to the capsulotomy [159]. In patients who previously underwent hip arthroscopy and present with symptomatic defects on the hip capsule, a reconstruction procedure should be considered [159]. Capsular reconstruction is a technically demanding procedure that requires advanced skills in hip arthroscopy [159]. Patients undergoing capsular reconstruction should be informed about the complexity of the procedure and the need for prolonged physical therapy to adequately restore hip function [159]. Data from a large sample confirm that hip microinstability can be successfully treated with plication, particularly in reducing unwanted symptoms and improving overall quality of life [79]. Short-term outcome studies suggest that capsular closure is safe and effective in nonarthritic patients undergoing hip arthroscopic procedures and may yield superior outcomes compared with unrepaired capsulotomy [233]. An iliofemoral ligament-preserving skip capsulotomy technique may reduce the risk of postoperative instability and pain, particularly in patients with borderline hip stability [235]. The acetabular labrum is a critical structure and should be repaired or reconstructed whenever possible to preserve its function, especially the negative suction seal function [52]. Acetabular labral tears are the most commonly noted pathology at hip arthroscopy and should be repaired or reconstructed whenever possible to restore the labral function of creating a negative pressure seal to the femoral head [52]. Removal of the acetabular labrum has been shown to lead to a shift in the femoral contact point toward the acetabular rim, a decrease in intra-articular fluid pressurization, and a loss of lateral restraint to femoral head motion [59]. Removal of the acetabular labrum has been shown to increase contact stresses between the articular cartilage of the femoral head and the acetabulum by 92% [59].

Other Considerations: This annotation outlines major current controversies relating to decision-making in hip arthroscopy for FAI, including preoperative and intraoperative imaging, labral management, capsular repair, and the diagnosis and treatment of hip instability [14]. The Warwick Agreement on femoroacetabular impingement syndrome is an international consensus statement on the diagnosis, treatment principles, and key terminology relating to FAI syndrome [141]. A physiotherapist-prescribed rehabilitation program may augment improvements in patient-reported outcomes following arthroscopy for FAI syndrome [141]. Significant variability exists in return-to-play protocols among institutions because of a lack of standardization [141]. Most rehabilitation protocols for hip arthroscopy are not evidence-based and rely on expert opinion [141]. A FAI syndrome-specific physical therapy program has the potential for a moderate to large positive effect on hip pain, function, and hip adductor strength [141]. Persons with chronic hip joint pain exhibit reduced hip muscle strength [141]. Patients with FAI demonstrate decreased hip flexion and extension strength when compared with reference persons and their contralateral hip [141]. Hip strength deficits are common in patients presenting with unilateral symptomatic FAI and occurred most commonly in hip abduction and flexion [141]. Strength deficits in hip flexion were associated with decreased function, loss of motion, and larger labral tears in patients with FAI and labral tears [141]. Persons with FAI syndrome exhibit altered pelvifemoral coordination regardless of weight-bearing status [141]. Decreased hip and/or lumbopelvic mobility may contribute to altered movement patterns at the hip in patients with FAI syndrome [141].

Osteotomy and Arthrodesis: A reconstructive acetabular osteotomy is the treatment of choice for deficient (anterolateral) acetabular coverage of the femoral head resulting in structural hip instability and acetabular rim overload [29]. The Bernese periacetabular osteotomy (PAO) has been popularized for acetabular reorientation and is now a mainstay of surgical treatment for hip dysplasia [29]. PAO is increasingly combined with hip arthroscopy in a single setting when labral pathology is present, with hip arthroscopy performed first [29]. Reported survival for PAO is 60% at 20-year follow-up [29]. Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) assessment of the glycosaminoglycan (GAG) content of the articular cartilage is predictive of outcome after PAO [29]. Low GAG content is associated with increased risk of failure of PAO [29]. Anterior overcorrection during PAO can produce acetabular retroversion and associated secondary FAI [29]. Hip arthrodesis is uncommonly used; it can be used to treat advanced hip degeneration (often posttraumatic) in a very specific patient population [9]. Indications for hip arthrodesis include being younger than 30 years, high activity level (e.g., manual labor), severe pain and stiffness, and normal adjacent joints (lumbar spine, contralateral hip, ipsilateral knee) [9]. Contraindications for hip arthrodesis include disease of the adjacent joints (lumbar spine, contralateral hip, ipsilateral knee), major limb-length discrepancy (>2.0 cm), and active infection [9]. The goals of surgical treatment for hip arthrodesis are to achieve bone apposition at the fusion site, rigid internal fixation, and early mobilization [9]. The most popular surgical techniques for hip arthrodesis include cobra plating through a lateral approach with a trochanteric osteotomy or plating through an anterior approach [9]. The preferred position for hip arthrodesis is 25° to 30° of hip flexion, 0° to 5° of adduction, and 5° to 10° of external rotation [9]. Hip arthrodesis achieves lasting pain relief and satisfactory clinical results in most patients [9]. The survivorship of hip arthrodesis can be limited by symptomatic degenerative disease of the adjacent joints [9]. Low back pain and osteoarthritis of the ipsilateral knee are the most common problems limiting hip arthrodesis survivorship [9]. Occasionally, conversion of hip fusion to total hip arthroplasty is needed [9]. The status of the hip abductor muscles should be determined preoperatively before converting hip fusion to total hip arthroplasty [9]. Trochanteric osteotomy is frequently needed for surgical exposure when converting hip fusion to total hip arthroplasty [9]. Rehabilitation after conversion of hip fusion to total hip arthroplasty is prolonged because of profound hip abductor weakness and associated limp [9]. Good clinical results are seen in most patients after conversion of hip fusion to total hip arthroplasty [9].

Total Hip Arthroplasty: Acetabular implant orientation targets for total hip arthroplasty are an abduction target of 30° to 50° and an anteversion target of 5° to 25° [30]. High abduction combined with high anteversion results in anterior instability with hip extension [30]. Low abduction combined with low anteversion results in posterior instability with hip flexion [30]. Combined acetabular and femoral implant anteversion targets are 35° to 40° for females and 30° to 35° for males [30]. Decreased femoral offset and inadequate leg length restoration can result in femoral neck imping

Complications¶

Iatrogenic Instability and Dislocation¶

Arthroscopic surgery performed without correction of underlying dysplasia is associated with poor clinical results due to persistent structural instability [194]. Patients with capsular laxity or surgical compromise of the capsule during peripheral component exposure are at risk for persistent symptoms from capsular incompetency [194]. Subtle postoperative instability may contribute to prolonged recovery and negatively influence outcomes [194]. Specific iatrogenic events include hip subluxation following arthroscopic debridement [33], anterior dislocation in patients with capsular laxity [34], and acute iatrogenic dislocation following hip impingement arthroscopic surgery [12].

General Arthroscopic Complications¶

Nerve dysfunction symptoms are considered an under-reported complication of hip arthroscopy [12]. Rare but serious systemic and local complications include abdominal compartment syndrome [12], venous thromboembolic disease [12], and fatal pulmonary embolism in a polytraumatized patient [12]. Femoral neck fracture has also been reported following arthroscopic management of femoroacetabular impingement [12].

Long-Term Failure and Revision¶

Persistent structural disease is the most common cause of repeat hip preservation surgery [12]. Inadequate femoral osteochondroplasty resulting in residual femoroacetabular impingement is a leading cause of failure after arthroscopy [223]. Capsular deficiency may be an increasingly common cause of pain, particularly in patients operated on with techniques that did not emphasize capsular closure [223]. Labral resection may place the hip at risk for early deterioration compared to labral reattachment [259]. At a minimum of 10-year follow-up, the total hip replacement conversion rate was 24.2% (23 patients) following hip arthroscopy for femoroacetabular impingement syndrome [225]. In the same cohort, 3 patients (3.2%) underwent hip arthroscopy revision for recurrent labral tears [225]. A second surgical procedure was required in 16 patients (16.8%) in less than 3 years following hip arthroscopy for femoroacetabular impingement syndrome [225]. The cumulative survival probability 10 years after hip arthroscopy surgery was 72.6% [225].

Periprosthetic Instability (Total Hip Arthroplasty Context)¶

Dislocation is the most common reason for revision surgery after arthroplasty within 2 years of injury [197]. The dislocation rate following total hip arthroplasty has declined steadily, with recent randomized trials reporting an incidence of 8% [197]. Use of a posterior approach increases the dislocation rate by a relative risk of 1.3 compared to other approaches [197]. High abduction combined with high anteversion is associated with anterior instability with hip extension [30], while low abduction combined with low anteversion is associated with posterior instability with hip flexion [30]. Decreased femoral offset and inadequate leg length restoration can result in femoral neck impingement against the pelvis or acetabular implant [30]. Risk factors for increased dislocation include female sex [30], osteonecrosis and femoral neck fractures [30], spinal fusion or limited lumbar spine mobility [30], neurologic conditions particularly Parkinson's disease [197], and revision total hip arthroplasty compared to primary total hip arthroplasty [30].

Recovery¶

Survivorship and Long-Term Outcomes: At a mean of 10 years postoperatively, 91% of hips remain preserved after femoroacetabular impingement surgery [83]. Patients undergoing primary hip arthroscopy with capsular repair experienced a high survivorship rate of 91% at a minimum 10-year follow-up [84], with a specific reported rate of 91.0% at minimum 10-year follow-up [86]. Good outcome scores and a low conversion rate to total hip arthroplasty were observed 10 years after hip arthroscopy for the treatment of femoroacetabular impingement [92]. Borderline hip dysplasia is not associated with significant differences in hip survivorship or patient-reported outcomes after primary hip arthroscopy for femoroacetabular impingement syndrome at minimum 10-year follow-up [40]. Concomitant hip arthroscopy and periacetabular osteotomy appears to be a safe and effective procedure with favorable mid-term outcomes that are durable compared to the short-term [21]. Bilateral hip arthroscopy achieved long-term outcomes and reoperation-free survivorship comparable to those of unilateral hip arthroscopy [211], and patients experience significant clinical benefit in both hips after staged bilateral hip arthroscopy [269].

Predictors of Outcome and Recovery Trajectory: Patients who experienced greater improvement in the first year after hip arthroscopy had superior 10-year outcome scores, fewer complications, and lower rates of reoperation compared with those who experienced minimal improvement in the same period [94]. Early functional improvements after hip arthroscopy, assessed by 6-month minimal clinically important difference (MCID), predicted clinically meaningful outcomes at 5-year follow-up [77]. Similarly, early improvements in patient-reported outcome measures (PROMs) following hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up [210]. Patients with a preoperative duration of femoroacetabular impingement syndrome (FAIS)-associated symptoms of 2 or more years prior to hip arthroscopy experience inferior outcomes and a lower frequency of clinically significant outcome improvement than patients with a shorter duration of symptoms at medium-to long-term follow-up [261]. In an adolescent cohort of symptomatic femoroacetabular impingement (FAI) patients who underwent hip arthroscopy, there is no difference in patient-reported outcome (PRO) measures when analyzing symptom duration by arbitrary time intervals or as a continuous variable [266]. Younger age and shorter duration of symptoms at time of surgery correlated with greater length of career and years played after hip arthroscopy in professional hockey players [272]. Female patients across a wide range of ages, body mass indices (BMIs), and symptom durations experience satisfactory 5-year outcomes following primary hip arthroscopy, but higher BMI is associated with reduced improvement in patient-reported outcomes [273]. Although short-term quality of life trajectories were similar between groups up to 12-weeks postoperative, long-term trajectories were less favourable for individuals with moderate-to-severe hip osteoarthritis [267]. At long-term follow-up, patients with concomitant lumbar spinal disease demonstrated significant improvements in hip function following hip arthroscopy for FAIS, but with lower modified Harris Hip Score (mHHS) and North American Hip Score (NAHS) scores and decreased rates of MCID achievement compared to controls [195]. There was no significant difference in Hip-RSI in patients with a history of anxiety and/or depression at any timepoint following hip arthroscopy for femoroacetabular impingement [270].

Contralateral Hip and Natural History: At a mean follow-up of 7.1 years, significant symptoms in the contralateral hip of patients with FAI were present in approximately 50% of patients [93]. At a mean follow-up of 6.7 years, significant symptoms in the contralateral hip of patients with FAI are present in 50.7% of patients, while 49.3% remain asymptomatic or minimally symptomatic [274]. A prospective longitudinal cohort study demonstrated a 51% rate of significant symptomatic development in the contralateral FAI hip at minimum 10-year follow-up, with 26% of patients experiencing symptoms at baseline [268]. The incidence of a symptomatic labral tear in asymptomatic contralateral hips with femoroacetabular impingement was 9% during 2 years of followup [90]. Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early osteoarthritis and to determine whether joint preserving hip surgery extends the life of the native hip joint [6]. The natural course of femoroacetabular impingement is a precursor to hip osteoarthritis [271].

Return to Sport and Athlete-Specific Outcomes: There is a severe lack of evidence on the athlete characteristics and clinical course of the nonreturning athletes, and the rate of subsequent hip procedures is unknown [35]. Hip-combined rotational morphology has little short-term impact on clinical outcomes after hip arthroscopy in patients with femoroacetabular impingement syndrome [31].

Evaluation and Reporting Limitations: Unlike other joints, there is no recognized systematic hip evaluation protocol to help prevent a missed diagnosis [19]. Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes, while measures of hip strength and range of motion are underreported, and current surgical outcomes are limited to mid-term follow-up time frames with inconsistent reporting [7]. Future clinical trials investigating the natural history and treatment of femoroacetabular impingement will require multimodal staging systems for hip osteoarthritis because the optimal system will differ based on the size of the study population, the specific objective in question, and the time frame in which the investigator expects to see the specified end point [82]. Careful evaluation of symptoms, hip disease, and expectations is needed before proceeding, and surgeons should proceed with caution in patients at least 50 years of age [38].

Key Evidence¶

[L4] High rates of FAI morphologic characteristics are present in patients with hip instability. [1] (10.1016/j.arthro.2015.07.021)
[L5] Evaluation of the patient with recurrent hip instability should be approached systematically with a thorough history and physical examination, along with a focused and targeted radiographic evaluation as indicated. [2] (10.1016/j.arth.2018.01.052)
[L4] Hips at greatest risk of failure have advanced arthrosis or a combination of impingement and instability preoperatively. [3] (10.1097/01.blo.0000150307.75238.b9)
[L5] Hip capsular preservation and closure should remain universal, particularly for patients with specific phenotypes requiring maximum surgical stability, as projected benefits outweigh risks and evidence suggests more robust clinical outcomes. [4] (10.1016/j.arthro.2024.03.015)
[L5] Hip dysplasia is a pathoanatomic osseous morphology associated with hip instability that may, in part, be due to hip capsular thickness. [5] (10.1016/j.arthro.2024.07.012)
[L4] Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early OA and to determine whether joint preserving hip surgery extends the life of the native hip joint. [6] (10.5435/jaaos-d-16-00532)
[L4] Patient-reported outcome measures and diagnostic imaging are the most frequently reported outcomes, while measures of hip strength and range of motion are underreported, and current surgical outcomes are limited to mid-term follow-up time frames with inconsistent reporting. [7] (10.1016/j.arthro.2017.11.037)
[L5] The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip. [8] (10.1016/j.arthro.2011.08.288)
[Paper] This article describes a comprehensive approach to interpretation of magnetic resonance examination of the hip, including optimal sequences and planes for identifying key pathology and quantifying bony morphology. [10] (10.1016/j.eats.2017.06.062)
[L4] The study showed a significant association between acetabular labral tears and structural abnormalities of the hip, with 87% of patients having at least one abnormality detectable on conventional radiographs. [11] (10.1097/01.blo.0000136903.01368.20)
[Paper] A thorough evaluation of the hip must include a comprehensive medical and surgical history focused on the hip joint, surrounding soft tissues, and associated structures, followed by a physical examination in multiple positions and gait assessment to distinguish between intra-articular and extra-articular contributors to hip pain. [13] (10.1016/j.eats.2017.03.027)
[L5] This annotation outlines major current controversies relating to decision-making in hip arthroscopy for femoroacetabular impingement, including preoperative and intraoperative imaging, labral management, capsular repair, and the diagnosis and treatment of hip instability. [14] (10.1302/0301-620x.104b5.bjj-2021-1553.r1)
[L5] The frequency of complications reported for hip arthroscopy for all indications is generally less than 1.5%, suggesting the procedure is safe. [15] (10.1007/s11999-008-0618-4)
[L5] The shelf acetabuloplasty technique offers limited invasiveness while allowing the comprehensive management of hip instability related to moderate dysplasia. [16] (10.1016/j.otsr.2019.01.004)
[L3] Durable outcomes (>9 years) with low revision rates can be expected after hip arthroscopic surgery with an approach that involves labral preservation where possible and careful attention to capsular closure in patients with borderline dysplasia. [17] (10.1177/03635465231161348)
[L4] Open surgical hip dislocation can benefit patients with complex pathology who are not candidates for hip arthroscopy, demonstrating high survivorship and improvements in patient-reported outcomes. [18] (10.1097/corr.0000000000003118)
[L5] [19] (10.1177/0363546513476281)
[L3] Long-term outcomes after isolated hip arthroscopy in borderline dysplasia patients are favorable with low revision rates and equivalent outcomes to a nondysplastic cohort. [20] (10.1177/2325967121s00561)
[L4] Concomitant hip arthroscopy and PAO appears to be a safe and effective procedure with favorable mid-term outcomes that are durable compared to the short-term. [21] (10.1016/j.arthro.2018.10.143)
[L5] Management of hip microinstability focuses on strengthening the dynamic stabilizers of the hip through focused physical therapy. [25] (10.1016/j.arthro.2021.12.001)
[L4] As there is a high percentage of overlapping (identical or similar) questions between the most commonly used hip-specific PROs for FAIS, multiple tests may be appropriate for use. [28] (10.1177/0363546521999403)
[L4] Hip-combined rotational morphology has little short-term impact on clinical outcomes after hip arthroscopy in FAIS patients. [31] (10.1002/arj.70330)
[L4] Some patients who suffer instability after hip arthroscopy for FAI do not show improved outcomes after surgery. [33] (10.1016/j.arthro.2013.09.050)
[L3] For determining the presence of a crossover sign, advanced 3D CT-generated hip models improve inter- and intra-observer agreement. [34] (10.1007/s00167-014-3315-8)
[L1] There is a severe lack of evidence on the athlete characteristics and clinical course of the nonreturning athletes, and the rate of subsequent hip procedures is unknown. [35] (10.1177/0363546520956292)
[L4] Hip arthroscopy in patients with generalized ligamentous laxity yields favorable outcomes and survivorship at 5-year minimum follow-up comparable to patients without generalized ligamentous laxity. [37] (10.1002/arj.70078)
[L5] Careful evaluation of symptoms, hip disease, and expectations is needed before proceeding, and surgeons should proceed with caution in patients at least 50 years of age. [38] (10.1016/j.arthro.2019.07.002)
[L4] Hip arthroscopy for symptomatic femoroacetabular impingement is a successful treatment in cases where dysplasia is present, demonstrating low complication rates, comparable outcomes to nondysplastic cases, and a high survivorship rate of 91% at minimum 10-year follow-up. [39] (10.1016/j.arthro.2024.08.022)
[L4] These findings support the use of hip arthroscopy as a durable and effective treatment for femoroacetabular impingement syndrome in this population. [40] (10.1177/03635465251405728)
[L3] [41] (10.1016/j.arthro.2011.12.004)
[L4] [45] (10.1177/03635465221075349)
[L5] [48] (10.1016/j.arthro.2024.06.003)
[Paper] FAI syndrome is defined as a motion-related clinical disorder of the hip with a triad of symptoms, clinical signs and imaging findings. [49] (10.1136/bjsports-2016-096743)
[L5] [50] (10.5435/00124635-201300001-00004)
[L3] A clinical diagnosis of hip osteoarthritis was found in approximately 22% of young patients undergoing hip arthroscopy within 2 years. [53] (10.1186/s12891-019-2646-5)
[L2] Radiographic evidence of FAI is common in active patients with hip complaints. [57] (10.1007/s11999-010-1233-8)
[L3] An isolated assessment of the LCEA is an oversimplistic approach that may jeopardize appropriate classification and may provide insufficient data to guide the treatment of hips with additional features of dysplasia and instability. [61] (10.1177/0363546518810731)
[L3] The overall prevalence of radiographic findings consistent with FAI in young patients presenting with hip pain was 60.5%. [62] (10.1177/0363546519896355)
[L5] Both acetabular and femoral morphology are critical to understanding femoroacetabular impingement and developing patient-specific treatments, as the complex interplay of versions influences outcomes and the presence of asymptomatic lesions. [63] (10.1016/j.arthro.2021.09.033)
[L4] Pathologic thickening of the hip capsule may contribute to restricted hip mobility on clinical examination. [65] (10.1007/s00167-018-4915-5)
[L5] The presence of apparently abnormal imaging findings in asymptomatic patients is well-known, and while preventive treatment cannot be justified for labral tears in the hip, patients should be informed that there is a 21% risk of developing symptoms. [67] (10.1097/corr.0000000000000606)
[L3] Approximately one in four patients with FAI presents with symptoms in the contralateral hip, and 16% of initially asymptomatic contralateral hips will develop symptoms during the next several years. [69] (10.1177/2325967116s00176)
[L5] Sensitivity, specificity, and intraobserver and interobserver observational consistency for femoroacetabular impingement radiographic diagnosis require confirmation; until radiologic criteria are confirmed, hip arthroscopic surgeons must rely on expert clinical examination. [72] (10.1016/j.arthro.2015.04.104)
[L3] In certain cases, hip arthroscopy can be cost-effective given a long enough duration of benefit and appropriate patient selection. [73] (10.1177/2325967120987538)
[L5] Hip arthroscopy for borderline hip dysplasia has a role with narrow indications, particularly in revision settings where the root cause of failure must be identified; instability-driven symptoms primarily indicate periacetabular osteotomy. [74] (10.1016/j.arthro.2024.06.026)
[L4] Current evidence supports for LT reconstruction predominantly for patients experiencing refractory instability following previous hip preservation procedures. [75] (10.1016/j.arthro.2021.01.022)
[L4] Hip arthroscopy for FAI results in increased patient-reported outcome measures at interval follow-up, with most patients reaching critical thresholds of minimal and satisfactory clinical improvement. [76] (10.1016/j.arthro.2019.06.020)
[L3] Early functional improvements after hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up. [77] (10.1177/23259671251352195)
[L3] Data from this large sample confirm that hip microinstability can be successfully treated with plication, particularly in reducing unwanted symptoms and improving overall quality of life. [79] (10.1016/j.jisako.2023.03.057)
[L1] Both hip arthroscopy and open surgical hip dislocation showed excellent and equivalent hip survival rates at medium-term follow-up with hip-specific outcome measures, demonstrating equivalence between groups. [80] (10.1177/0363546515587719)
[L4] Periacetabular osteotomy used as a salvage procedure for patients with hip instability recalcitrant to prior arthroscopy demonstrated substantial improvement in patient-reported outcome measures and radiographic correction of acetabular coverage. [81] (10.2106/jbjs.20.00087)
[L5] Future clinical trials investigating the natural history and treatment of femoroacetabular impingement will require multimodal staging systems for hip osteoarthritis because the optimal system will differ based on the size of the study population, the specific objective in question, and the time frame in which the investigator expects to see the specified end point. [82] (10.5435/00124635-201300001-00008)
[L2] At a mean of 10 years postoperatively, 91% of hips remain preserved. [83] (10.2106/jbjs.25.01341)
[L3] Patients undergoing primary hip arthroscopy with capsular repair experienced a high survivorship rate of 91% at a minimum 10-year follow-up. [84] (10.1177/03635465241248603)
[L3] Patients undergoing primary hip arthroscopy with capsular repair experienced a high rate of survivorship of 91.0% at minimum 10-year follow-up. [86] (10.1177/2325967123s00008)
[L3] Acetabular chondral flap type visualized during hip arthroscopy correlates with radiographic markers of hip impingement and hip instability. [87] (10.1177/0363546519871065)
[L5] Concomitant procedures represent a powerful solution for the treatment of severe hip dysplasia and intra-articular pathologies resulting from instability or combined FAIS. [88] (10.1016/j.arthro.2024.10.023)
[L5] The exact definition of 'impingement' eludes the current literature, and while dynamic MRI has potential to better define hip impingement, it is not yet optimized for widespread clinical use; clinicians must 'treat the patient, not the MRI.' [89] (10.1016/j.arthro.2019.05.009)
[L4] The incidence of a symptomatic labral tear in these asymptomatic hips was 9% during 2 years of followup. [90] (10.1097/corr.0000000000000567)
[L4] [92] (10.1097/corr.0000000000001778)
[L2] At a mean follow-up of 7.1 years, significant symptoms in the contralateral hip of patients with FAI were present in approximately 50% of patients. [93] (10.1177/03635465221119509)
[L3] Patients who experienced greater improvement in the first year after hip arthroscopy had superior 10-year outcome scores, fewer complications, and lower rates of reoperation compared with those who experienced minimal improvement in the same period. [94] (10.1177/03635465251342119)
[L4] These findings suggest age-related differences in the morphology and kinematics of the native hip, specifically regarding the position of the femoral head within the acetabulum. [95] (10.1002/jor.24806)
[L3] [117] (10.1016/j.arthro.2018.07.042)
[L4] The clinical impingement sign is challenged as a specific diagnostic test, and the study emphasizes the early nature of hip pathology in athletes. [129] (10.1016/j.otsr.2010.09.005)
[L4] Increased cam morphology remained a significant contributor to reduced internal rotation but did not affect hip flexion. [130] (10.1016/j.arthro.2020.02.044)
[L1] Biomechanical evidence supports closure of the capsule after hip arthroscopy to reverse the significant effects of capsulotomy. [135] (10.1016/j.arthro.2021.04.004)
[L5] Lumbopelvic stability and restoring appropriate hip biomechanics and muscle firing patterns are key to successful return to activity and sport. [137] (10.1002/arj.70175)
[L4] Hip strength deficits were common in patients presenting with unilateral symptomatic FAI and occurred most commonly in hip abduction and flexion. [139] (10.1016/j.arthro.2015.04.095)
[Paper] The puncture capsulotomy technique preserves the native anatomy and biomechanics of the hip joint by leaving the iliofemoral ligament intact, thereby eliminating the risk of gross anterior dislocation and avoiding postoperative range-of-motion restrictions associated with traditional capsulotomy. [145] (10.1016/j.eats.2017.08.036)
[L5] Clinical identification of combined impingement and dysplasia is imperative to potentially improve patient outcomes. [148] (10.1002/arj.70215)
[L4] Gait analysis of FAIS patients after hip arthroscopy demonstrated small, albeit significant, changes in postoperative hip kinetics and kinematics; however, these changes did not correlate with the large, clinically significant improvements in PROs at 1 year after surgery. [150] (10.1177/23259671221121352)
[L5] The presence of FAI morphology does not necessarily mean that FAI is the primary source of hip pain; other less common causes, such as osteoid osteoma, should be included in the differential diagnosis, especially when atypical clinical and radiological signs are found. [151] (10.1007/s00167-014-2985-6)
[L4] Hip impingement in those with FAIS may routinely occur at hip flexion angles below 90° in neutral rotation, with males engaging at higher flexion angles than females. [163] (10.1002/arj.70005)
[L5] Future studies should define thresholds for labrum size to guide clinical decision-making and develop an algorithm combining symptoms, clinical examination, and radiological signs to determine whether borderline dysplastic hips require arthroscopy or bony correction. [164] (10.1016/j.arthro.2021.06.032)
[L3] Considering the high prevalence of radiographic hip findings reminiscent of FAI in asymptomatic Asian populations, it will be important to determine whether FAI-related morphologic features are a cause of hip pain when considering surgery in Asian patients. [165] (10.1007/s11999-016-5013-y)
[L5] Clinicians should evaluate for the Beighton score and additional radiographic factors suggestive of instability in patients with combined borderline hip dysplasia and excessive femoral anteversion, as these findings may portend inferior outcomes after arthroscopic treatment in isolation, making open procedures like periacetabular osteotomy a more reliable option for symptomatic hip instability. [168] (10.1016/j.arthro.2022.12.001)
[L3] Extraarticular FAI is an uncommon source of impingement symptoms, often missed due to prior hip surgery, and seems more common in younger, female patients. [169] (10.1007/s11999-014-4001-3)
[L2] Acetabular and femoral osseous abnormalities commonly are associated with labral tears, and recognition of these abnormalities is important to optimize surgical treatment of patients with symptomatic labral disease. [170] (10.1097/01.blo.0000181147.86058.74)
[L1] When surgery is indicated, age 40 years should not be considered an independent contraindication to arthroscopic acetabular labral repair. [171] (10.1177/03635465241263595)
[L2] Hip arthroscopic surgery yields meaningful improvements in hip function in the majority of patients, regardless of sex. [172] (10.1177/0363546515610535)
[L3] Understanding of hip disorder-specific chondral damage patterns may be useful for the development of arthroscopic classification of hip disorders and may lead to the establishment of treatment guidelines. [178] (10.1007/s00167-014-3297-6)
[Paper] [184] (10.1016/j.jisako.2026.101188)
[L4] The indication for surgery should be established cautiously when degenerative changes are present. [185] (10.1007/s00402-016-2427-7)
[L4] [190] (10.1055/s-0038-1676448)
[L5] [191] (10.1016/j.arthro.2023.12.010)
[L1] Hip-related QOL improved in both groups by clinically meaningful amounts. [192] (10.1136/bjsports-2025-110986)
[L1] Thus, age over 40 years should not be considered a contraindication to arthroscopic acetabular labral repair. [193] (10.1177/0363546521990789)
[L4] [194] (10.5435/jaaos-21-07-s53)
[L3] At long-term follow-up, HSS patients demonstrated significant improvements in hip function following HA for FAIS, but with lower mHHS and NAHS scores and decreased rates of MCID achievement compared to controls. [195] (10.1177/2325967126s00438)
[L3] It is recommended to perform routine intraoperative repair of the articular capsule at the end of hip arthroscopy, as this has a positive influence on the functional results at short-term follow-up. [198] (10.1186/s12891-024-07894-0)
[L4] Arthroscopic management of femoroacetabular impingement syndrome in patients aged ≥40 years results in significant and durable improvements in pain and function, with preservation of the native hip in most cases, although rates of conversion to total hip arthroplasty range from 2.9% to 13.2% across included studies. [199] (10.1002/arj.70557)
[L3] In a small sample, simultaneous bilateral hip arthroscopy is shown to be safe and effective, resulting in similar improvements in patient-reported outcomes at 1-year follow-up compared with staged bilateral procedures. [200] (10.1016/j.arthro.2016.01.047)
[Paper] Hyaluronic acid injections appear to confer reliable short-term improvements in hip pain and function for symptomatic FAI, but potential intermediate-term and long-term benefit has not yet been demonstrated. [202] (10.2106/jbjs.rvw.24.00211)
[L3] Patients 40 years who underwent primary hip arthroscopy with labral repair demonstrated a hip preservation rate of 78%, significant and durable improvement in PROMs, and high rates of satisfaction at a minimum 10-year follow-up. [204] (10.1177/03635465241270291)
[L3] Hip arthroscopy for management of femoroacetabular impingement and labral tears in patients aged less than 50 demonstrates favorable and safe mid-term outcomes. [205] (10.5435/jaaos-d-17-00258)
[L3] There are both modifiable and non-modifiable pre-operative factors that have the potential to predict a return to high functional status after hip arthroscopy for FAI. [206] (10.1177/2325967118s00070)
[L3] [208] (10.1002/arj.70611)
[L3] Early improvements in PROMs following hip arthroscopy, assessed by 6-month MCID, predicted clinically meaningful outcomes at 5-year follow-up. [210] (10.1177/2325967125s00193)
[L3] Bilateral hip arthroscopy achieved long-term outcomes and reoperation-free survivorship comparable to those of unilateral hip arthroscopy. [211] (10.1177/03635465251412678)
[L2] Three of the 4 studies showed significant associations between positive injection response and superior postoperative outcomes, with positive responders achieving higher Hip Outcome Score Activities of Daily Living, Hip Outcome Score-Sports, Nonarthritic Hip Score, and Patient-Reported Outcome Measure Information System scores (P = .003-0.045) and higher minimum clinically important difference/patient acceptable symptomatic state achievement rates. [212] (10.1002/arj.70477)
[L1] Targeted rehabilitation should integrate hip-centric and core stabilization exercises, but longitudinal studies are needed to validate therapeutic efficacy. [213] (10.1186/s13018-025-06135-x)
[L5] Nonoperative treatment remains the first line of treatment for most FAI patients and should not be abandoned in favor of early surgery; hip arthroscopy is an appropriate viable option only after failure to improve after a full course of physical therapy is established. [215] (10.1016/j.arthro.2023.05.009)
[L4] No evidence exists on outcomes following non-operative management of FAI with concomitant Tönnis Grade 2 or more OA of the hip. [216] (10.1007/s00167-022-07274-y)
[L3] Classifying acetabular dysplasia into 3 groups based on the plane of instability could optimize the planning of PAO by giving a better understanding of the 3-dimensional deformity. [222] (10.1177/0363546521992108)
[L5] [223] (10.5435/jaaos-d-16-00928)
[L4] [225] (10.1016/j.arthro.2024.08.012)
[L3] Hip arthroscopy for the treatment of FAIS in competitive athletes and nonathletes produced clinically meaningful outcomes in both patient groups. [226] (10.1177/0363546519885359)
[L3] Preoperative MRI did not alter indications for primary hip arthroscopy in patients aged 40 years and younger with a history, physical examination findings, and radiographs concordant with FAIS. [227] (10.1177/23259671221144776)
[L1] In our meta-analysis, hip arthroscopy is statistically superior to conservative treatment in both long-term and short-term effects. [228] (10.1186/s13018-022-03187-1)
[L2] [229] (10.1097/corr.0000000000001706)
[L3] [231] (10.1177/0363546515612448)
[L1] Short-term outcome studies suggest that capsular closure is safe and effective in nonarthritic patients undergoing hip arthroscopic procedures and may yield superior outcomes compared with unrepaired capsulotomy. [233] (10.1016/j.arthro.2017.06.030)
[L3] A computer-assisted analysis of young adult hip radiographs generally demonstrates substantial to excellent levels of interobserver reliability for most parameters. [234] (10.1177/0363546514542797)
[L5] This technique may reduce the risk of postoperative instability and pain, particularly in patients with borderline hip stability, and facilitate earlier functional recovery. [235] (10.1016/j.eats.2025.103769)
[L5] Plain radiographs are key in the initial assessment of patients suspected of femoroacetabular impingement, while computed tomography scans allow for accurate definition of deformities and are particularly helpful in revision hip arthroscopy. [237] (10.1016/j.csm.2016.02.002)
[L4] In addition, MRI is useful to diagnose or rule out non-FAI pathology, ascertain labral pathology, and outline hip alignment; these methods of preoperative planning are complementary. [239] (10.1016/j.asmr.2021.07.015)
[L2] In joint-preserving hip surgery, lesions of the ligamentous-fossa-foveolar complex (LFFC) are very common, with 65% of hips showing substantial damage. [241] (10.1097/corr.0000000000003825)
[L3] [242] (10.1177/03635465241255950)
[L4] In patients with FAIS, both MRI and MRA have excellent reliability for quantifying hip capsular thickness. [244] (10.1016/j.asmr.2023.100874)
[L3] Patients with borderline hip dysplasia and radiographic evidence of hip instability, as measured by the FEAR index (≥2), may achieve similar improvement in 2-year outcomes compared to those with radiographically stable hips after arthroscopic treatment of FAIS. [245] (10.1016/j.arthro.2021.10.012)
[L2] In addition, multidirectional CTA demonstrated promising diagnostic strength for hip lesions such as labral tears and chondral defects. [246] (10.1177/23259671221143459)
[L4] Unstable hips demonstrated a more recessed acetabular dome when compared to stable hips. [248] (10.1016/j.injury.2024.111601)
[L2] [251] (10.1007/s00167-019-05503-5)
[L4] Radiological evidence of symptomatic femoroacetabular impingement was not uncommon in these Japanese patients with hip pain, with cam deformity findings being the most common. [252] (10.1302/0301-620x.96b2.32680)
[L3] Most patients with unilateral symptomatic FAI and radiographic diagnosis of bilateral FAI became symptomatic relatively quickly and most of them underwent subsequent surgical intervention in the contralateral hip. [253] (10.1097/corr.0000000000000699)
[L2] Significant agreement of angular measurements for hip morphology exists between ZTE MRI and CT imaging. [254] (10.1177/0363546519878170)
[L3] A narrow posterior joint space on a False Profile radiograph does not correlate with posterior joint cartilage degeneration in hip preservation patients. [255] (10.1016/j.arthro.2020.07.023)
[L4] Small changes in acetabular rim morphology on the order of 0.5 mm may be the difference between symptomatic FAIS and the unaffected hip. [257] (10.1016/j.asmr.2019.06.001)
[L3] The current results suggest the importance of preserving the labrum and show that resection may put the hip at risk for early deterioration. [259] (10.1007/s11999-016-5114-7)
[L3] Patients with a preoperative duration of FAIS-associated symptoms of 2 or more years prior to hip arthroscopy experience inferior outcomes and a lower frequency of clinically significant outcome improvement than patients with a shorter duration of symptoms at medium-to long-term follow-up. [261] (10.1016/j.arthro.2019.08.032)
[L4] Radiographic indicators of FAI are very common among athletes evaluated at the National Football League Scouting Combine subjected to radiographic examination for the clinical suspicion of hip disease. [263] (10.1016/j.arthro.2012.03.005)
[L3] Our study shows that surgeons experienced in FAI/Dysplasia have higher interrater agreement in making a diagnosis of such hip disorders than other hip surgeons, however, this remains only fair when based on x- rays and moderate when other imaging is included. [264] (10.1016/j.arthro.2013.09.034)
[L3] Preoperative MRI for patients with FAIS aged 40 or under undergoing primary hip arthroscopy provides little to no actionable clinical information with respect to the labrum or cartilage and may negatively impact outcomes by delaying access to care unnecessarily by at least two weeks. [265] (10.1177/2325967121s00609)
[L4] In an adolescent cohort of symptomatic FAI patients who underwent hip arthroscopy, there is no difference in PRO measures when analyzing symptom duration by arbitrary time intervals or as a continuous variable. [266] (10.1016/j.arthro.2023.03.028)
[L3] Although short-term trajectories were similar between groups up to 12-weeks postoperative, long-term trajectories were less favourable for individuals with moderate-to-severe hip osteoarthritis. [267] (10.1016/j.jisako.2025.100478)
[L2] This prospective longitudinal cohort study demonstrated a 51% rate of significant symptomatic development in the contralateral FAI hip at minimum 10-year follow-up, with 26% of patients experiencing symptoms at baseline. [268] (10.1177/2325967125s00187)
[L3] Patients experience significant clinical benefit in both hips after staged bilateral hip arthroscopy. [269] (10.1016/j.arthro.2022.10.048)
[L3] There was no significant difference in Hip-RSI in patients with a history of anxiety and/or depression at any timepoint. [270] (10.1177/2325967124s00194)
[L5] Management of Femoroacetabular Impingement starts with good diagnosis, as the natural course is a precursor to hip osteoarthritis. [271] (10.1177/2325967121s00848)
[L4] Younger age and shorter duration of symptoms at time of surgery correlated with greater length of career and years played after hip arthroscopy. [272] (10.1177/0363546516650649)
[L3] Female patients across a wide range of ages, BMIs, and symptom durations experience satisfactory 5-year outcomes following primary hip arthroscopy, but higher BMI is associated with reduced improvement in patient-reported outcomes. [273] (10.1016/j.arthro.2023.06.035)
[L2] At a mean follow-up of 6.7 years, significant symptoms in the contralateral hip of patients with FAI are present in 50.7% of patients, while 49.3% remain asymptomatic or minimally symptomatic. [274] (10.1177/2325967121s00278)

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[31] Hip‐Combined Rotational Morphology Has Little Short‐Term Impact on Clinical Outcomes Following Hip Arthroscopy in Patients With Femoroacetabular Impingement Syndrome. Arthroscopy. 2026. DOI: 10.1002/arj.70330

[33] Capsular Repair for Instability Following Hip Arthroscopy for Femoroacetabular Impingement: Preliminary Outcomes and Description of Surgical Technique. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2013.09.050

[34] Inter‐ and intra‐observer agreement of femoroacetabular impingement (FAI) parameters comparing plain radiographs and advanced, 3D computed tomographic (CT)‐generated hip models in a surgical patient cohort. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3315-8

[35] Can We Identify Why Athletes Fail to Return to Sport After Hip Arthroscopy for Femoroacetabular Impingement Syndrome? A Systematic Review and Meta-analysis. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546520956292

[37] Hip Arthroscopy Yields Favorable Outcome, Return‐to‐Sport Rate, and 5‐Year Survivorship in Athletic Population With Generalized Ligamentous Laxity in the Treatment of Femoroacetabular Impingement and Labral Tears. Arthroscopy. 2026. DOI: 10.1002/arj.70078

[38] Hip Arthroscopy for Femoroacetabular Impingement Patients Older Than 50 Years—Proceed With Caution. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.07.002

[39] Patients With Dysplasia Achieve Similar Outcomes and Survivorship to Nondysplastic Patients 10 Years After Hip Arthroscopy for Femoroacetabular Impingement. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.08.022

[40] Borderline Hip Dysplasia Not Associated With Significant Differences in Hip Survivorship or Patient-Reported Outcomes After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Study With Minimum 10-Year Follow-up. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251405728

[41] Diagnostics of Femoroacetabular Impingement and Labral Pathology of the Hip: A Systematic Review of the Accuracy and Validity of Physical Tests. Arthroscopy. 2012. DOI: 10.1016/j.arthro.2011.12.004

[43] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Radiography.

[44] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Introduction.

[45] Effectiveness of Nonoperative Management of Hip Microinstability. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465221075349

[48] Editorial Commentary: The Hip “Windshield Wiper Sign”: An Osteochondral Defect of the Anterolateral Femoral Head, Predicts Instability and Allows Planning of Combined Arthroscopic Cartilage Therapy and Periacetabular Osteotomy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.06.003

[49] The Warwick Agreement on femoroacetabular impingement syndrome (FAI syndrome): an international consensus statement. British Journal of Sports Medicine. 2016. DOI: 10.1136/bjsports-2016-096743

[50] Femoroacetabular Impingement: Defining the Condition and its Role in the Pathophysiology of Osteoarthritis. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00004

[51] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Summary.

[52] Orthopaedic Knowledge Update Sports Medicine 6. Athletic Hip Injuries > Summary.

[53] The two-year incidence of hip osteoarthritis after arthroscopic hip surgery for femoroacetabular impingement syndrome. BMC Musculoskeletal Disorders. 2019. DOI: 10.1186/s12891-019-2646-5

[54] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Diagnosis.

[55] Aaos Comprehensive Orthopaedic Review 3. The Pediatric Hip* > I. Developmental Dysplasia of the Hip.

[57] Radiographic Prevalence of Femoroacetabular Impingement in a Young Population with Hip Complaints Is High. Clinical Orthopaedics & Related Research. 2010. DOI: 10.1007/s11999-010-1233-8

[59] Orthopaedic Knowledge Update Sports Medicine 6. Athletic Hip Injuries > Acetabular Labral Tears.

[61] Mild or Borderline Hip Dysplasia: Are We Characterizing Hips With a Lateral Center-Edge Angle Between 18° and 25° Appropriately?. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518810731

[62] The Prevalence of Radiographic Findings of Structural Hip Deformities for Femoroacetabular Impingement in Patients With Hip Pain. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546519896355

[63] Editorial Commentary: Both Femoral Acetabular Anteversion and Retroversion May Contribute to the Effect of Femoroacetabular Impingement: What’s Your Version?. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.09.033

[65] Hip capsular thickness correlates with range of motion limitations in femoroacetabular impingement. Knee Surgery, Sports Traumatology, Arthroscopy. 2018. DOI: 10.1007/s00167-018-4915-5

[67] CORR Insights®: Acetabular Labral Tears Are Common in Asymptomatic Contralateral Hips With Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2019. DOI: 10.1097/corr.0000000000000606

[69] The Fate of the Contralateral Hip in Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2016. DOI: 10.1177/2325967116s00176

[72] Editorial Commentary: Radiographic Inclusion and Exclusion Diagnostic Criteria for Femoroacetabular Impingement Require Confirmation. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.04.104

[73] Cost-Effectiveness of Hip Arthroscopy for Treatment of Femoroacetabular Impingement Syndrome and Labral Tears: A Systematic Review. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967120987538

[74] Editorial Commentary: Revision Hip Arthroscopy in Patients With Borderline Dysplasia Has a Role: Indications Are Narrow Versus Periacetabular Osteotomy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.06.026

[75] Ligamentum Teres Reconstruction May Lead to Improvement in Outcomes Following a Secondary Hip Arthroscopy for Symptomatic Microinstability: A Systematic Review. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.01.022

[76] Outcome Trends After Hip Arthroscopy for Femoroacetabular Impingement: When Do Patients Improve?. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.06.020

[77] Six-Month Functional Scores Predict 5-Year Achievement of the Minimal Clinically Important Differences After Hip Arthroscopy for Symptomatic Acetabular Labral Tears. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/23259671251352195

[79] Primary Labral Reconstruction Versus Labral Repair In Patients With Femoroacetabular Impingement: An Inverse Propensity Score Weighted Analysis of Patient Reported Outcomes and Subsequent Surgery Risk. Journal of ISAKOS. 2023. DOI: 10.1016/j.jisako.2023.03.057

[80] Arthroscopic Versus Open Treatment of Femoroacetabular Impingement. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515587719

[81] Periacetabular Osteotomy as a Salvage Procedure. Journal of Bone and Joint Surgery. 2020. DOI: 10.2106/jbjs.20.00087

[82] Staging of Hip Osteoarthritis for Clinical Trials on Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/00124635-201300001-00008

[83] Survivorship of Femoroacetabular Impingement Surgery at Mean 10-Year Follow-up. Journal of Bone and Joint Surgery. 2026. DOI: 10.2106/jbjs.25.01341

[84] Long-term Survivorship and Outcomes of Patients Without Dysplasia Undergoing Capsular Repair During Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241248603

[86] Paper 08: Long Term Survivorship and Outcomes of Patients Undergoing Capsular Repair and Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967123s00008

[87] The “Outside-In” Lesion of Hip Impingement and the “Inside-Out” Lesion of Hip Dysplasia: Two Distinct Patterns of Acetabular Chondral Injury. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519871065

[88] Editorial Commentary: Arthroscopic Treatment of Mild Hip Dysplasia Can Result in Excellent Outcome and Avoid More Invasive Periacetabular Osteotomy. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.10.023

[89] Editorial Commentary: What Exactly Is Impingement—Can Dynamic Magnetic Resonance Imaging “See” Impingement in Femoroacetabular Impingement?. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.05.009

[90] Acetabular Labral Tears Are Common in Asymptomatic Contralateral Hips With Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2018. DOI: 10.1097/corr.0000000000000567

[92] Good Outcome Scores and Low Conversion Rate to THA 10 Years After Hip Arthroscopy for the Treatment of Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001778

[93] Factors Associated With Disease Progression in the Contralateral Hip of Patients With Symptomatic Femoroacetabular Impingement: A Minimum 5-Year Analysis. The American Journal of Sports Medicine. 2022. DOI: 10.1177/03635465221119509

[94] One-Year Outcomes Predict 10-Year Outcomes in Patients Undergoing Hip Arthroscopy for Femoroacetabular Impingement. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465251342119

[95] Age‐related differences in morphology and kinematics of the native hip. Journal of Orthopaedic Research. 2020. DOI: 10.1002/jor.24806

[96] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > 2. Arthrology > Hip (Fig. 2.49).

[99] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Osseous and Ligamentous Anatomy.

[100] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > IV. Hip Capsule and Ligaments.

[101] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Introduction.

[103] Aaos Comprehensive Orthopaedic Review 3. Surgical Anatomy of the Hip > V. Hip Joint Muscles.

[111] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Anatomy and Biomechanics, Evaluation, Clinical Examination, and Imaging of the Hip > Imaging.

[117] The Effect of Complete Tearing of the Ligamentum Teres in Patients Undergoing Primary Hip Arthroscopy for Femoroacetabular Impingement and Labral Tears: A Match‐Controlled Study. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2018.07.042

[119] Orthopaedic Knowledge Update Sports Medicine 6. Imaging of the Hip > Summary.

[129] Descriptive epidemiology of mechanical hip pathology in adults under 50 years of age. Prospective series of 292 cases: Clinical and radiological aspects and physiopathological review. Orthopaedics & Traumatology: Surgery & Research. 2010. DOI: 10.1016/j.otsr.2010.09.005

[130] The Bipolar Hip: How Acetabular and Femoral Pathomorphology Affects Hip Motion in Femoral Acetabular Impingement Syndrome. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2020. DOI: 10.1016/j.arthro.2020.02.044

[135] Hip Capsular Management in Patients With Femoroacetabular Impingement or Microinstability: A Systematic Review of Biomechanical Studies. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2021. DOI: 10.1016/j.arthro.2021.04.004

[137] Rehabilitation Following Hip Arthroscopy for Femoroacetabular Impingement and Labral Repair. Arthroscopy. 2026. DOI: 10.1002/arj.70175

[138] Orthopaedic Knowledge Update. Developmental Dysplasia of the Hip* > Adolescent HIP Dysplasia.

[139] Hip Strength Deficits in Patients With Symptomatic Femoroacetabular Impingement and Labral Tears. Arthroscopy. 2015. DOI: 10.1016/j.arthro.2015.04.095

[141] Orthopaedic Knowledge Update Sports Medicine 6. Hip Rehabilitation > Annotated References.

[142] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Early Degenerative Changes of the Hip > Hip Dysplasia > Treatments.

[145] Puncture Capsulotomy During Hip Arthroscopy for Femoroacetabular Impingement: Preserving Anatomy and Biomechanics. Arthroscopy Techniques. 2017. DOI: 10.1016/j.eats.2017.08.036

[147] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Bony Abnormalities.

[148] The Literature Shows Heterogeneity and Promise for the Role of Hip Arthroscopy Combined With Periacetabular Osteotomy for Dysplastic Patients, But Nuanced Decision Making and Further Research Are Required. Arthroscopy. 2026. DOI: 10.1002/arj.70215

[150] Correlating Biomechanical Gait Analysis With Patient-Reported Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/23259671221121352

[151] Atypical hip pain: coexistence of femoroacetabular impingement (FAI) and osteoid osteoma. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-2985-6

[159] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Treatment.

[163] Impingement in Patients With Femoroacetabular Impingement Syndrome Routinely Occurs Below 90° of Hip Flexion. Arthroscopy. 2026. DOI: 10.1002/arj.70005

[164] Editorial Commentary: Hip Dysplasia—Arthroscopic Femoroacetabular Impingement Versus Periacetabular Osteotomy: Do Not FEAR the Size of the Next Step. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.06.032

[165] What is the Prevalence of Radiographic Hip Findings Associated With Femoroacetabular Impingement in Asymptomatic Asian Volunteers?. Clinical Orthopaedics & Related Research. 2016. DOI: 10.1007/s11999-016-5013-y

[168] Editorial Commentary: Evaluate for the Beighton Score and Additional Radiographic Signs of Instability Prior to Proceeding With Hip Arthroscopy in Patients With Combined Borderline Hip Dysplasia and Excessive Femoral Anteversion. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2022.12.001

[169] What Are the Demographic and Radiographic Characteristics of Patients With Symptomatic Extraarticular Femoroacetabular Impingement?. Clinical Orthopaedics & Related Research. 2015. DOI: 10.1007/s11999-014-4001-3

[170] Acetabular and Femoral Radiographic Abnormalities Associated with Labral Tears. Clinical Orthopaedics and Related Research. 2005. DOI: 10.1097/01.blo.0000181147.86058.74

[171] Hip Arthroscopy Versus Physical Therapy for the Treatment of Symptomatic Acetabular Labral Tears in Patients Older Than 40 Years: 24-Month Results From a Randomized Controlled Trial. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241263595

[172] Sex Differences in Self-Reported Hip Function Up to 2 Years After Arthroscopic Surgery for Femoroacetabular Impingement. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515610535

[177] Campbell S Operative Orthopaedics 4 Volume Set. OPEN REDUCTION AND REPAIR OF PATELLAR DISLOCATION > HIP.

[178] Hip morphology influences the pattern of articular cartilage damage. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3297-6

[179] Orthopaedic Knowledge Update Sports Medicine 6. Hip Microinstability > Soft Tissue > Hip Capsule.

[182] Orthopaedic Knowledge Update Sports Medicine 6. Athletic Hip Injuries > Hip Instability.

[184] Prehabilitation for Femoroacetabular Impingement Syndrome: Intervention development using the Medical Research Council framework. Journal of ISAKOS. 2026. DOI: 10.1016/j.jisako.2026.101188

[185] Arthroscopic treatment of femoroacetabular impingement shows persistent clinical improvement in the mid-term. Archives of Orthopaedic and Trauma Surgery. 2016. DOI: 10.1007/s00402-016-2427-7

[190] Rehabilitation for Femoroacetabular Impingement: Conservative Care and Postoperative Practice. The Journal of Hip Surgery. 2018. DOI: 10.1055/s-0038-1676448

[191] Clinical Equipoise in the Management of Patients With Femoroacetabular Impingement Syndrome and Concomitant Tönnis Grade 2 Hip Osteoarthritis or Greater: An International Expert‐Panel Delphi Study. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.12.010

[192] Physiotherapist-led treatment for femoroacetabular impingement syndrome (the PhysioFIRST study): an assessor-blinded, limited disclosure randomised controlled trial. British Journal of Sports Medicine. 2026. DOI: 10.1136/bjsports-2025-110986

[193] Hip Arthroscopy Versus Physical Therapy for the Treatment of Symptomatic Acetabular Labral Tears in Patients Older Than 40 Years: A Randomized Controlled Trial. The American Journal of Sports Medicine. 2021. DOI: 10.1177/0363546521990789

[194] Overview of Treatment Options, Clinical Results, and Controversies in the Management of Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2013. DOI: 10.5435/jaaos-21-07-s53

[195] Poster 136. Patients With Concomitant Lumbar Spinal Disease Have Less Significant Improvement Than Those Without Lumbar Spinal Disease at 10-Year Follow-up Following Hip Arthroscopy for Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2026. DOI: 10.1177/2325967126s00438

[197] Rockwood And Green S Fractures In Adults. 51: Hip Dislocations and Femoral Head Fractures > Prosthesis Dislocation.

[198] A retrospective cohort study: dual cannula combined with modified shoelace continuous capsular closure technique versus nonrepair in hip arthroscopic surgery of femoroacetabular impingement. BMC Musculoskeletal Disorders. 2024. DOI: 10.1186/s12891-024-07894-0

[199] Hip Arthroscopy for Femoroacetabular Impingement Syndrome in Patients Aged ≥40 Years Produces Durable Functional Improvement With Moderate Survivorship Compared With Younger Cohorts: A Systematic Review. Arthroscopy. 2026. DOI: 10.1002/arj.70557

[200] Simultaneous Versus Staged Bilateral Hip Arthroscopy in the Treatment of Femoroacetabular Impingement. Arthroscopy. 2016. DOI: 10.1016/j.arthro.2016.01.047

[202] Femoroacetabular Impingement: Critical Analysis Review of Current Nonoperative Treatments. JBJS Reviews. 2025. DOI: 10.2106/jbjs.rvw.24.00211

[204] Ten-Year Outcomes in Patients Aged 40 Years and Older After Primary Arthroscopic Treatment of Femoroacetabular Impingement With Labral Repair. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241270291

[205] Hip Arthroscopy for Femoroacetabular Impingement and Labral Tears in Patients Younger than 50 Years: Minimum Five-year Outcomes, Survivorship, and Risk Factors for Reoperations. Journal of the American Academy of Orthopaedic Surgeons. 2019. DOI: 10.5435/jaaos-d-17-00258

[206] Pre-operative Predictors of Return to High Functional Status after Hip Arthroscopy for Femoroacetabular Impingement at 2-year Minimum Follow-up. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118s00070

[208] Healed Acetabular Labrum on Postoperative Magnetic Resonance Imaging Is Associated With Superior Achievement of Clinically Significant Outcomes After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: Minimum 2‐Year Follow‐Up. Arthroscopy. 2026. DOI: 10.1002/arj.70611

[210] Poster 88: Six-Month Functional Scores Predict 5-Year Outcomes after Hip Arthroscopy for Symptomatic Acetabular Labral Tears. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00193

[211] Bilateral Hip Arthroscopy Compared with Unilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Analysis of Long-term Outcomes and Procedural Timing. The American Journal of Sports Medicine. 2026. DOI: 10.1177/03635465251412678

[212] Positive Response to Preoperative Intra‐articular Anesthetic Injection Suggests Favorable Outcomes After Hip Arthroscopy in Patients With Femoroacetabular Impingement Syndrome: A Systematic Review. Arthroscopy. 2026. DOI: 10.1002/arj.70477

[213] Hip muscle changes in femoroacetabular impingement: a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research. 2025. DOI: 10.1186/s13018-025-06135-x

[215] Editorial Commentary: Nonoperative Management Is the First Line of Treatment for Hip Femoroacetabular Impingement in Adolescents: Children Are Not Little Adults!. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.05.009

[216] No evidence exists on outcomes of non‐operative management in patients with femoroacetabular impingement and concomitant Tönnis Grade 2 or more hip osteoarthritis: a scoping review. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07274-y

[222] Correlation of Patient-Reported Outcomes After Periacetabular Osteotomy With Femoral Head Coverage and Acetabular Orientation: A Single-Center Cohort Study. The American Journal of Sports Medicine. 2021. DOI: 10.1177/0363546521992108

[223] Approach to the Patient With Failed Hip Arthroscopy for Labral Tears and Femoroacetabular Impingement. Journal of the American Academy of Orthopaedic Surgeons. 2020. DOI: 10.5435/jaaos-d-16-00928

[225] High Survival Rate and Satisfaction at More Than 11‐Year Follow‐Up After Hip Arthroscopy for Femoroacetabular Impingement Syndrome: Impact of Preoperative Functional Scores, Osteoarthritis, and Chondrolabral Junction Damage on Failure. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.08.012

[226] Comparing Outcomes of Competitive Athletes Versus Nonathletes Undergoing Hip Arthroscopy for Treatment of Femoroacetabular Impingement Syndrome. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519885359

[227] Evaluating the Need for Preoperative MRI Before Primary Hip Arthroscopy in Patients 40 Years and Younger With Femoroacetabular Impingement Syndrome: A Multicenter Comparative Analysis. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671221144776

[228] Conservative therapy versus arthroscopic surgery of femoroacetabular impingement syndrome (FAI): a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research. 2022. DOI: 10.1186/s13018-022-03187-1

[229] The New Bern Chondrolabral Classification Is Reliable and Reproducible. Clinical Orthopaedics & Related Research. 2021. DOI: 10.1097/corr.0000000000001706

[231] Is Subchondral Acetabular Edema or Cystic Change on MRI a Contraindication for Hip Arthroscopy in Patients With Femoroacetabular Impingement?. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515612448

[233] Should the Capsule Be Repaired or Plicated After Hip Arthroscopy for Labral Tears Associated With Femoroacetabular Impingement or Instability? A Systematic Review. Arthroscopy. 2017. DOI: 10.1016/j.arthro.2017.06.030

[234] Interobserver and Intraobserver Reliability of the Radiographic Analysis of Femoroacetabular Impingement and Dysplasia Using Computer-Assisted Measurements. The American Journal of Sports Medicine. 2014. DOI: 10.1177/0363546514542797

[235] Minimally Invasive Hip Arthroscopy for Femoroacetabular Impingement Using Iliofemoral Ligament–Preserving Skip Capsulotomy for Cam Resection. Arthroscopy Techniques. 2025. DOI: 10.1016/j.eats.2025.103769

[237] Imaging in Hip Arthroscopy for Femoroacetabular Impingement. Clinics in Sports Medicine. 2016. DOI: 10.1016/j.csm.2016.02.002

[239] Preoperative Dynamic Hip Examination Under Fluoroscopic Guidance Enhances the Understanding of Femoroacetabular Impingement Pathology and Treatment Planning. Arthroscopy, Sports Medicine, and Rehabilitation. 2021. DOI: 10.1016/j.asmr.2021.07.015

[241] Severe Damage to the Ligamentous-Fossa-Foveolar Complex Is Common in Patients Undergoing Surgical Hip Dislocation for Femoroacetabular Impingement. Clinical Orthopaedics & Related Research. 2026. DOI: 10.1097/corr.0000000000003825

[242] Association Between Severity of Chondrolabral Junction Breakdown and Functional Outcomes After Hip Arthroscopy for Acetabular Labral Tears. The American Journal of Sports Medicine. 2024. DOI: 10.1177/03635465241255950

[244] Magnetic Resonance Imaging and Magnetic Resonance Arthrography Are Both Reliable and Similar When Measuring Hip Capsule Thickness in Patients With Femoroacetabular Impingement Syndrome. Arthroscopy, Sports Medicine, and Rehabilitation. 2024. DOI: 10.1016/j.asmr.2023.100874

[245] Patients With a High Femoroepiphyseal Roof With Concomitant Borderline Hip Dysplasia and Femoroacetabular Impingement Syndrome Do Not Demonstrate Inferior Outcomes Following Arthroscopic Hip Surgery. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2022. DOI: 10.1016/j.arthro.2021.10.012

[246] Combined 3-Dimensional CT and Multidirectional CT Arthrography for Femoroacetabular Impingement and Hip Lesions: A Cross-sectional Study Comparing Imaging and Hip Arthroscopic Surgery Findings. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/23259671221143459

[248] Acetabular dysplasia and posterior wall fractures: The missing link?. Injury. 2024. DOI: 10.1016/j.injury.2024.111601

[251] Despite patient-reported outcomes improve, patients with femoroacetabular impingement syndrome do not increase their objectively measured sport and physical activity level 1 year after hip arthroscopic surgery. Results from the HAFAI cohort. Knee Surgery, Sports Traumatology, Arthroscopy. 2019. DOI: 10.1007/s00167-019-05503-5

[252] Are cam and pincer deformities as common as dysplasia in Japanese patients with hip pain?. The Bone & Joint Journal. 2014. DOI: 10.1302/0301-620x.96b2.32680

[253] Bilateral Femoroacetabular Impingement: What is the Fate of the Asymptomatic Hip?. Clinical Orthopaedics & Related Research. 2019. DOI: 10.1097/corr.0000000000000699

[254] Evaluation of Osseous Morphology of the Hip Using Zero Echo Time Magnetic Resonance Imaging. The American Journal of Sports Medicine. 2019. DOI: 10.1177/0363546519878170

[255] A Narrow Posterior Joint Space on a False Profile Radiograph Does Not Correlate With Posterior Joint Cartilage Degeneration in Hip Preservation Patients. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2020. DOI: 10.1016/j.arthro.2020.07.023

[257] Mirror Image Modeling of Acetabular Rim Thickness Differences in Patients With Unilateral Femoroacetabular Impingement Syndrome. Arthroscopy, Sports Medicine, and Rehabilitation. 2019. DOI: 10.1016/j.asmr.2019.06.001

[259] Labral Reattachment in Femoroacetabular Impingement Surgery Results in Increased 10-year Survivorship Compared With Resection. Clinical Orthopaedics & Related Research. 2017. DOI: 10.1007/s11999-016-5114-7

[261] Preoperative Duration of Symptoms Is Associated With Outcomes 5 Years After Hip Arthroscopy for Femoroacetabular Impingement Syndrome. Arthroscopy. 2019. DOI: 10.1016/j.arthro.2019.08.032

[263] Radiographic Findings of Femoroacetabular Impingement in National Football League Combine Athletes Undergoing Radiographs for Previous Hip or Groin Pain. Arthroscopy. 2012. DOI: 10.1016/j.arthro.2012.03.005

[264] Reliability in the Diagnosis of Femoroacetabular Impingement and Dysplasia Among Hip Surgeons. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2013.09.034

[265] Paper 45: Preoperative MRI Offers Minimal Clinical Utility, Delays Access to Hip Arthroscopy, and Lacks Cost-Effectiveness in Patients Aged 40 or Under with Classic Femoroacetabular Impingement Syndrome: A Retrospective 5-Year Analysis. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/2325967121s00609

[266] Timing From Symptom Onset to Hip Arthroscopy Does Not Affect Patient‐Reported Outcome Measures for the Treatment of Femoroacetabular Impingement in Adolescent Patients. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.03.028

[267] Quality of Life Trajectories in Patients with Femoroacetabular Impingement Syndrome After Arthroscopic Surgery: Impact of Osteoarthritis Severity. Journal of ISAKOS. 2025. DOI: 10.1016/j.jisako.2025.100478

[268] Poster 79: Contralateral Hip Disease Progression in Patients with Femoroacetabular Impingement: 10-year Follow-up Prospective Cohort. Orthopaedic Journal of Sports Medicine. 2025. DOI: 10.1177/2325967125s00187

[269] Staged Bilateral Hip Arthroscopy for Femoroacetabular Impingement Syndrome: Index Surgery Patient Reported Outcome Measures Predict Contralateral Surgery Results at 2 Years. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2022.10.048

[270] Poster 225: Assessing Hip-RSI in Patients that Undergo Hip Arthroscopy for Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/2325967124s00194

[271] The Management of Femoroacetabular Impingement. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967121s00848

[272] Predictors of Length of Career After Hip Arthroscopy for Femoroacetabular Impingement in Professional Hockey Players. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516650649

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