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Anatomical Structures

Hip joint anatomy and morphological variations, focusing on the impact of version and coverage on FAI, dysplasia, and degenerative joint disease.

104 citationsUpdated Aug 2026

Overview

Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement [1]. Patients with slipped femoral epiphysis treated conservatively can remain symptom-free for many years [1]. Additional studies are needed to determine protective or adaptive factors in patients with abnormal hip anatomy who do not develop early osteoarthritis [2]. Additional studies are needed to determine whether joint-preserving hip surgery extends the life of the native hip joint [2].

Surgical approaches to the hip joint and femur respect basic functional anatomy to afford adequate exposure and good results [6]. Surgical approaches to the hip joint and femur describe basic anatomical features, problems, and danger points to minimize complications [6]. Precise knowledge of anatomy can minimize complications in the direct anterior approach to the hip joint [70]. Clear goals in the surgical approach can facilitate visualization and instrumentation placement in the direct anterior approach to the hip joint [70].

Comprehensive knowledge of regional anatomy is essential for safe and effective aspiration and injection of the lower extremity [15]. Knowledge of procedural indications and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [15]. Thorough knowledge of anatomy is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20]. Knowledge of alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20].

Easily identifiable anatomic landmarks allow safe, reproducible physeal-sparing, anatomic anterior cruciate ligament reconstructions without intra-operative x-ray [23]. Proximal femoral osteotomies in adolescence have different indications and treatment strategies [24]. Standard anterior, anterolateral, and posterolateral portals in hip arthroscopy allow proper accessibility of the central compartment [25]. Standard anterior, anterolateral, and posterolateral portals in hip arthroscopy have slight limitations in the posteromedial corner [25]. The range of knee anatomy in patients scheduled for total knee arthroplasty is wide [71].

Anatomy & Pathophysiology

Biomechanics and Kinematics

Capsular Management: Capsular management during hip arthroscopy must allow for improved exposure without compromising stability and kinematics of the hip [7]. Hip Joint Biomechanics: An understanding of hip joint biomechanics allows clinicians to assimilate the effects of motions and deformations resulting from forces acting on the joint to guide appropriate medical interventions [32]. Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force [35]. The hip abductor moment arm varies substantially throughout the hip's range of motion in the coronal plane [42]. The hip center of rotation trajectory varies under common movements, highlighting the importance of hip translation on physiologic range of motion [48].

Normal Kinematics: Healthy hip joints exhibit activity-dependent kinematics with coordinated pelvic and femoral dynamic movements during weight-bearing activities [38]. A six degree-of-freedom robot is appropriate to reproduce the physiological range of motion of the hip joint [47]. The distinctive phase-dependent biomechanical response of the hip demonstrates a coordinated control strategy for balance recovery due to gait perturbations [43]. Subject-specific gait combined with inverse dynamic analysis provides pre-processing parameters for finite element simulation to enable more accurate biomechanical analysis of the hip joint [39]. Smartphone applications are practical measurements for hip rotational angles when compared with three-dimensional motion analysis [50].

Pathological Kinematics and Loading: Abnormal hip and knee joint loading during walking after total hip replacement has a biomechanical background originating from hip geometry reconstruction [33]. Despite individualized reconstruction of biomechanical hip geometry, objective gait analysis failed to show a benefit for custom-made prostheses in total hip arthroplasty [34]. Degenerative hips experience more abnormal hip kinematics that leads to higher articulating surface forces and stresses within the acetabulum compared to normal or postoperative implanted hips [44]. Abnormal hip kinematics in women with patellofemoral pain appears to be the result of diminished hip-muscle performance as opposed to altered femoral structure [45]. Increased stress and a shift in contact location were observed in simulated models of femoroacetabular impingement despite simulating lower degrees of hip flexion and internal rotation [51].

Clinical Correlations and Outcomes

Patient-Reported Outcomes: Patients reported significant improvement in function and pain at 1 year postoperatively after arthroscopy for femoroacetabular impingement syndrome, but these improvements did not correlate with improvements in hip kinematics [49].

Prevention and Assessment: Identifying biomechanical mechanisms that place young athletes at risk for hip injury enables anticipatory guidance and preventative strategies [36]. A normative database of hip and knee kinematics utilized by football athletes was developed [41].

Soft Tissue Constraints

Acetabular Labrum: The acetabular labrum bears a direct mechanical role during hip motion, and resecting the labrum might be detrimental for hip joint biomechanics by modifying strain distribution between the acetabulum and femur [40].

Classification

Hip Deformity Architecture: A classification system for architectural hip deformities enables the repeatable distinction of five distinct types of deformities [37].

Developmental Dysplasia of the Hip (DDH): A classification system based on the greater trochanter of the femur distinguishes various types of DDH to aid in surgical strategy formulation [59]. Additionally, the classification of developmental patterns illustrates varying directional changes in lower-extremity length discrepancies and their dependence on underlying biological phenomena [60].

Medial Knee Anatomy: The medial knee exhibits a consistent three-layered anatomical pattern [5]. Specific nomenclature for the superficial medial ligament and posteromedial capsule is suggested over the term 'posterior oblique ligament' based on this consistent three-layered pattern [5].

Medial Meniscus Ramp Tears: A surgically relevant classification system for medial meniscus ramp tears, based on tear morphology, allows for the evaluation of differing repair patterns and their effects on postoperative clinical outcomes [58].

Paediatric Hip Ultrasound: Geometric measurements in paediatric hip ultrasound are reliably interpreted and may serve as a quality measurement [55]. Morphological features in paediatric hip ultrasound are generally poorly interpreted but improve with simpler binary classification [55].

Condylar-Stabilized (CS) Implants: A classification system for condylar-stabilized designs allows for the appropriate grouping and comparison of distinct CS implants [57].

Pes Anserinus: A proposed classification of pes anserinus morphology may improve the planning of surgical procedures [53].

Femoral Torsion vs. Anteversion: Accurate anatomic localization enables precise terminology that distinguishes femoral torsion from anteversion [18].

Medial Patellofemoral Ligament (MPFL): The medial patellofemoral ligament demonstrates variable and elongated morphology, differentiating it from the adductor tubercle and Gerdy’s tubercle, which demonstrated the most consistent morphology [65].

Femoro-epiphyseal Acetabular Roof Index: The modified approach to measuring the femoro-epiphyseal acetabular roof index has better intraobserver and interobserver reliability compared with the original index for Type II and III sourcil types [64].

Other Considerations: Individual evaluation of the obturator neurovascular bundle, specifically the high prevalence of venous corona mortis, should be performed prior to surgical interventions [3]. Detailed density maps of bony anatomy may assist surgical providers in planning interventions for unilateral femoral acetabular impingement [4]. The psoas valley is a consistent bony landmark with important anatomical variations [11].

Clinical Presentation

A thorough appreciation of hip anatomy and normal function is critical for identifying pathologies and developing successful treatment strategies [8]. For lateral hip pain, understanding the abductor musculature anatomy, specific clinical signs, and imaging findings leads to appropriate diagnosis and management [46]. In cases of concurrent hip and spine pathology, overlapping symptomatology presents a substantial diagnostic challenge with no consensus on which condition to address first [52]. Extra-articular etiologies of pain represent an important subset of hip disorders that can be accurately identified through physical examination and imaging [54].

Plain radiographic evaluation remains the initial diagnostic modality for femoroacetabular impingement (FAI) [9]. Three-dimensional imaging, including MRI and CT, is often obtained to evaluate labral and cartilage pathology, define bony anatomy, and assist in surgical planning [9]. Advanced imaging studies have enhanced the understanding of hip vascular anatomy and its clinical implications for orthopaedic treatment [10]. Providing detailed density maps of the bony anatomy may further assist surgical providers in planning interventions [4]. The anatomy of the psoas valley serves as a consistent bony landmark [11].

Individual evaluation of the obturator neurovascular bundle, including the high prevalence of venous corona mortis, should be performed prior to any surgical interventions [3]. The medial side of the knee exhibits a consistent three-layered anatomical pattern [5]. Specific nomenclature for the superficial medial ligament and posteromedial capsule should be used rather than the term 'posterior oblique ligament' [5].

With an understanding of normal and abnormal gait, a directed history and physical examination, and a differential diagnosis based on limp type, patient age, and likely anatomic site, the orthopaedist can take a selective approach to diagnostic testing [12]. The goal of treatment for hip disease in young, active patients is to establish a clear diagnosis, assess severity, and plan a surgical strategy to make the hip as structurally normal as possible [13].

Femoroacetabular impingement morphologic features and labral injuries are common in asymptomatic patients [14]. 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 [16]. The study provides information to determine the prevalence of morphological variations associated with FAI according to age and sex in the general population [17]. Females with FAI had more profound symptomatology and milder morphologic abnormalities [56]. Males with FAI had a higher activity level, larger morphologic abnormalities, more common combined-type morphologies, and more extensive intra-articular disease [56].

Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement, as the procedure allows patients to remain symptom-free for many years [1]. Additional studies are needed to determine protective or adaptive factors in patients with abnormal anatomy who do not develop early osteoarthritis [2].

Investigations

MRI: Three-dimensional imaging, including MRI and CT, is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning in femoroacetabular impingement [9]. Magnetic resonance imaging-based 3-dimensional models of the pelvis and hip using machine learning for automatic bone segmentation in dynamic hip impingement simulation are feasible with routine MRI and short image acquisition time [63]. Patient-specific 3-dimensional MRI-based dynamic simulation of hip impingement and range of motion can replace 3D CT-based simulation for patients with femoroacetabular impingement [72]. The authors intend to change their clinical practice to use MRI-based 3D models for future clinical practice instead of CT-based 3D models for femoroacetabular impingement [72]. MRI documentation should be established as a standard examination post-reduction for congenital dislocation of the hip [69]. Magnetic resonance imaging is effective in localizing neurilemoma of the saphenous nerve presenting as pain in the knee [74]. MRI scanning is necessary to establish whether some patients have an occult hip fracture [66]. Imaging for osteonecrosis is recommended in athletes with hip dislocation and subluxation [75]. Evidence suggests 4- to 6-week magnetic resonance imaging for those with suspicious findings in the femoral head after hip dislocation and subluxation [75]. Pathologic changes seen on MRI were symptomatic in less than two thirds of elite female ballet dancers [82].

CT: Computed tomography provides a noninvasive method for studying anatomy in live subjects, allowing for the detailed mapping of position, size, and orientation of the abductor muscles of the hip [79]. CT has higher interobserver reliability than MRI for measuring femoral anteversion [62]. Diagnosis of femoral anteversion should not rely exclusively on physical examination or radiologic criteria [62]. Standard MRI scans cannot replicate the appropriate level of detail for anterior inferior iliac spine morphology classification compared to 3D CT [68]. Preoperative planning CT scan should not be eliminated from the patient pathway for anterior inferior iliac spine visualization based on current data [68]. Future refinements in 3D MRI techniques may eventually allow them to replace low-dose 3D CT scans for anterior inferior iliac spine visualization [68]. ioMRI cannot yet replace CT scans for thorough evaluation of osseous morphology dimensions for femoroacetabular impingement [83]. ioMRI may be considered when CT is contraindicated for evaluation of osseous morphology dimensions for femoroacetabular impingement [83].

Other Considerations: Accurate anatomic localization enables precise terminology distinguishing femoral torsion from anteversion [18]. Several consistent anatomical levels were identified for single axial MR slice to facilitate muscle size and fatty infiltration measures at the hip [61]. Consistent anatomical levels for single axial MR slice provide the basis for reliable and accurate data synthesis and improvements in the validity of future between studies analyses [61]. Measurements of femoral version on CT strongly correlated with those on MRI in adolescent patients [87]. Follow-up at 3 months is recommended for those with suspicious findings in the femoral head after hip dislocation and subluxation [75].

Treatment

Non-Operative Management

Non-operative management is often sufficient for specific pediatric and degenerative conditions. Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement, as the condition allows patients to remain symptom-free for many years [1]. Moderate nonprogressive coxa vara in childhood often does not require surgery [92]. Most patients with peritrochanteric space disorders or lateral hip pain tend to resolve symptoms with non-surgical management in the mid-term [84]. Conversely, non-operative treatments for lower-extremity rotational problems in children are usually ineffective [97]. Non-operative management of proximal rectus femoris avulsion injuries is associated with highly variable periods of convalescence, poor return to preinjury level of function, and high risk of injury recurrence [93]. For fragility fractures of the pelvis, operative management should be considered for patients failing a brief period of non-operative management, although prospective randomised trials are needed to provide improved evidence for this intervention [85].

Operative Management

Indications: Surgical management of coxa vara in childhood is indicated for progressive, painful, unilateral deformity or leg-length discrepancy [92]. Surgical treatment for osteochondritis dissecans following Legg-Calve-Perthes disease is indicated when bone fragments fail to heal and symptoms progress despite conservative treatment [27]. Surgical options for peritrochanteric space disorders should be evaluated when non-surgical management fails [84]. In non-elite patients, persistent grade 2 or 3 medial collateral ligament laxity beyond 12 weeks in the setting of anterior cruciate ligament rupture should prompt combined anterior cruciate ligament reconstruction with medial collateral ligament repair and reconstruction [95]. When nonoperative treatment fails, operative management of soft tissue cam impingement in adolescents yields patient-reported outcomes comparable to those in patients with osseous cam lesions [88].

Surgical Approach / Technique: Proximal femoral osteotomies in adolescence have various indications and treatment strategies [24]. Rotational osteotomies for lower-extremity rotational problems in children are effective but associated with significant complication rates [97]. Surgical treatment limited to localized recontouring of the head-neck profile in cam impinging femurs may fail to address significant components of the underlying abnormality [73]. Repair of horizontal cleavage meniscus tears results in substantial improvements in patient-reported outcomes, acceptable midterm clinical healing rates, and low reoperation/failure rates [76]. Anatomic anterolateral ligament reconstruction does not reduce anterolateral rotational laxity [81]. Subchondroplasty for post-traumatic bone marrow lesions of the medial femoral condyle showed improvements in clinical outcomes and bony histology but no difference in the progression of medial compartment post-traumatic gonarthrosis in a pre-clinical canine model [77].

Surgical Planning and Anatomical Considerations

Surgical approaches to the hip joint and femoral shaft should respect basic functional anatomy to afford adequate exposure and good results while minimizing complications [6]. The anterior hip capsule is thinner in dysplastic hips, and capsular thickness and intra-substance changes vary, which could alter capsular management strategies [67]. Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques is essential for safe and effective aspiration and injection of the lower extremity [15]. A thorough knowledge of anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs during anterior cruciate ligament reconstruction [20]. Using easily identifiable anatomic landmarks allows safe, reproducible anatomic anterior cruciate ligament reconstructions without the need for intra-operative x-ray [23]. The use of standard anterior, anterolateral, and posterolateral portals in hip arthroscopy allows proper accessibility of the central compartment, with slight limitations in the posteromedial corner [25]. The anterior intrapelvic approach requires an in-depth understanding of the historically 'nonorthopaedic' surgical anatomy and associated risks [29]. Preoperative roentgenographic evaluation helps confirm adequacy of coverage and guides surgical decision-making for osteotomies about the hip in children, though exact criteria are not yet established [80].

Complications

Surgical Approach and Exposure: Surgical approaches to the hip joint and femoral shaft require identification of basic anatomical features, problems, and danger points to ensure adequate exposure and good results while minimizing complications [6]. The anterior intrapelvic approach carries associated risks related to its historically 'nonorthopaedic' surgical anatomy [29]. Medial hip arthroscopy portals did not cause damage to the neurovascular structures evaluated [100].

Instability and Graft Placement: Anatomic femoral attachment is critical to a well-functioning medial patellofemoral ligament reconstruction and minimizes complications, whereas nonanatomic placement can cause significant changes in graft isometry [99]. Longer-term follow-up is required to determine whether the excellent results of isolated polyethylene insert exchange for flexion instability after primary total knee arthroplasty are durable over time [28].

Implant Alignment and Technique: Femoral component coronal alignment in fixed-bearing unicompartmental knee arthroplasty may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship [26]. Long-term follow-up is necessary to evaluate any differences in long-term durability between gap balancing and measured resection techniques in simultaneous bilateral total knee arthroplasty [19].

Soft Tissue and Functional Outcomes: Functional deficits persist due to soft tissue damage from arthrosis requiring longer recovery time independent of the surgical approach [30]. Reconstruction of neglected developmental dysplasia by total hip arthroplasty with subtrochanteric shortening osteotomy is a demanding technique with a high rate of related complications [90].

Other Considerations: Anatomical reduction is not necessary for good function in slipped femoral epiphysis with severe displacement, and the procedure allows patients to remain symptom-free for many years [1]. Although no detrimental clinical effect was found in intermediate-term follow-up of cementless total hip replacement with a modular femoral head with an extended flange-reinforced neck, the findings warrant concern for adverse effects after more long-term follow-up [78].

Recovery

Light activity (weeks): Evidence does not specify a week range for light activity or desk work return.

Full activity (months): Evidence does not specify a month range for full activity, manual work, or sport return.

Complete recovery / outcome plateau (months): Long-term functional outcomes for anterior cruciate ligament (ACL) reconstruction are influenced by preoperative conditioning, with structured preoperative exercise programs resulting in better long-term results [22]. Thigh muscle changes associated with ACL injury and reconstruction differ at long-term evaluation compared to early changes, suggesting treatment strategies may need adjustment to preserve long-term function [91]. For femoroacetabular impingement (FAI) surgery, clinical and functional results, activity levels, and quality of life improved statistically at an average follow-up of 12 months in patients with residual bony prominence [89]. Modular bicompartmental knee arthroplasty provides comparable functional outcomes to total knee arthroplasty at short- to mid-term follow-up but demonstrates poor long-term survivorship [94]. Femoral component coronal alignment affects long-term clinical outcomes in fixed-bearing unicompartmental knee arthroplasty, though it does not impact short-term outcomes or 10-year survivorship [26].

Rehabilitation protocol: Evidence does not specify PT phasing, immobilisation duration, weight-bearing progression, or brace removal timing.

Functional milestones: Functional deficits persist due to soft tissue damage from arthrosis, requiring longer recovery times independent of the surgical approach (minimally invasive vs. transgluteal) for total hip arthroplasty [30]. Cementless total hip replacement with subtrochanteric femoral shortening for severe developmental dysplasia of the hip demonstrates reconstruction of the original joint center and good mid-term results [31].

Other Considerations: FAI is defined as a pathologic mechanical process involving morphologic abnormalities and vigorous motion that damages soft-tissue structures [21]. Morphologic features of FAI and labral injuries are common in asymptomatic patients [14]. FAI morphology is common in young adults and predisposes to later osteoarthritis [21]. Recognition of FAI and early intervention before the degenerative process is advanced is likely to considerably impact the natural history of the disease, delaying the onset of end-stage arthritis in young patients [101]. More long-term data are needed to define the natural history of pincer deformities and FAI in younger cohorts [21]. Biomechanical and long-term clinical studies will continue to be performed to better understand the importance of the labrum and how to restore its function in labral base refixation [86]. The study aimed to determine the long-term objective and subjective outcome of untreated articular cartilage defects observed at the time of ACL reconstruction [103]. Further studies are required to understand if two-incision technique femoral tunnel placement in ACL reconstruction can ameliorate proprioception and clinical outcome at long-term follow-up [96]. Surgical treatment indications for osteochondritis dissecans following Legg-Calve-Perthes disease include failure of bone fragments to heal and progression of symptoms despite conservative treatment [27]. The natural history of Legg-Calvé-Perthes disease is often favorable for children younger than 6 years and poor for children older than 8 to 10 years [102]. Morphological variants in the human fetal hip joint were not significantly different from normal joints in linear measurements, suggesting they are examples of morphological variability within the range of normal development rather than deformities [104]. Specific morphological characteristics on pelvis radiographs of avascular necrosis hips were predictive for poor outcome at a very young age in developmental dysplasia of the hip [105].

Key Evidence

• [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. [2] (10.5435/jaaos-d-16-00532)
• [Paper] Individual evaluation of this risky anatomical structure should be done prior to any surgical interventions. [3] (10.1016/j.injury.2016.04.032)
• [L4] Providing detailed density maps of the bony anatomy may also assist surgical providers in planning interventions. [4] (10.1177/2325967124s00187)
• [L5] The study delineated a consistent three-layered anatomical pattern of the medial knee, suggesting the use of specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament'. [5] (10.2106/00004623-197961010-00011)
• [L5] The management of the capsule is critical and must allow for improved exposure without compromising stability and kinematics of the hip. [7] (10.1016/j.arthro.2011.08.288)
• [L5] Plain radiographic evaluation remains the initial diagnostic modality, while three-dimensional imaging such as MRI and CT is often obtained for the evaluation of labral and cartilage pathology, definition of bony anatomy, and surgical planning. [9] (10.5435/00124635-201300001-00006)
• [L5] Advanced imaging studies have enhanced understanding of this vascular anatomy and its clinical implications for orthopaedic treatment. [10] (10.5435/jaaos-d-15-00237)
• [L4] This review highlights the importance of the anatomy of the psoas valley which is a consistent bony landmark. [11] (10.1186/s12891-020-03241-1)
• [L5] With an understanding of normal and abnormal gait, a directed history and physical examination, and the development of a differential diagnosis based on the type of limp, the patient's age, and the anatomic site that is most likely affected, the orthopaedist can take a selective approach to diagnostic testing. [12] (10.5435/00124635-200103000-00003)
• [L5] The goal of treatment is to establish a clear diagnosis, assess severity, and plan a surgical strategy to make the hip as structurally normal as possible. [13] (10.5435/00124635-200812000-00002)
• [L4] FAI morphologic features and labral injuries are common in asymptomatic patients. [14] (10.1016/j.arthro.2014.11.042)
• [L5] Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques are essential for safe and effective aspiration and injection. [15] (10.5435/jaaos-d-16-00762)
• [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. [16] (10.1016/j.arthro.2021.09.033)
• [L3] This study provides information to determine the prevalence of these anatomic variants in the general population. [17] (10.1177/2325967120977892)
• [L4] Accurate anatomic localization enables precise terminology distinguishing femoral torsion from anteversion. [18] (10.1007/s11999-014-4000-4)
• [L1] Long-term follow-up will be necessary to evaluate any differences in long-term durability. [19] (10.1016/j.arth.2019.10.002)
• [L5] A thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs despite careful planning and adherence to proper surgical technique. [20] (10.1177/2325967116652122)
• [L5] FAI is defined as a pathologic mechanical process involving morphologic abnormalities and vigorous motion that damages soft-tissue structures; while FAI morphology is common in young adults and predisposes to later OA, more long-term data are needed to define the natural history of pincer deformities and FAI in younger cohorts. [21] (10.5435/00124635-201300001-00004)
• [L2] A structured preoperative exercise program resulted in better post operative functional outcomes at the long term. [22] (10.1016/j.arthro.2013.07.252)
• [L4] Using these easily identifiable landmarks allows safe, reproducible anatomic ACL reconstructions without the need for intra-operative x-ray. [23] (10.1016/j.arthro.2011.03.072)
• [L4] The aim of this review is to show the different ways of proximal femoral osteotomies and their indications after having done a selective literature research. [24] (10.1055/a-1023-4679)
• [L5] In hip arthroscopy, the use of the standard anterior, anterolateral, and posterolateral portals allows proper accessibility of the central compartment, with slight limitations in the posteromedial corner. [25] (10.1016/j.arthro.2013.05.017)
• [L3] Femoral component coronal alignment may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. [26] (10.1016/j.arth.2020.07.070)
• [L4] Longer-term follow-up is required to determine whether these results are durable over time. [28] (10.1016/j.arth.2020.01.006)
• [L5] This review aims to provide an in-depth understanding of the AIP approach with a focus on the historically 'nonorthopaedic' surgical anatomy and associated risks. [29] (10.5435/jaaos-d-24-01050)
• [L3] Functional deficits persist due to soft tissue damage from arthrosis requiring longer recovery time independent of the surgical approach. [30] (10.1055/s-0030-1250590)
• [Paper] A reconstruction of the original joint center and good mid-term results are demonstrated. [31] (10.1007/s00402-003-0554-4)
• [L5] An understanding of hip joint biomechanics constitutes an important background for the diagnosis and treatment of hip disorders, allowing clinicians to assimilate the effects of motions and deformations resulting from forces acting on the joint to guide appropriate medical interventions. [32] (10.1016/j.arthro.2010.01.027)
• [L2] Abnormal hip and knee joint loading during walking after THR has a biomechanical background originating from hip geometry reconstruction. [33] (10.1016/j.arth.2019.07.027)
• [L3] Despite the individualized reconstruction of the biomechanical hip geometry, objective gait analysis failed to show a benefit. [34] (10.1007/s00402-008-0717-4)
• [L5] Both osseous and soft tissue constraints are important to hip biomechanics depending upon the direction of applied force. [35] (10.1007/s00167-012-2255-4)
• [L3] Identifying biomechanical mechanisms that place young athletes at risk for hip injury enables anticipatory guidance and preventative strategies for these patients. [36] (10.1177/2325967113s00059)
• [L4] The classification system enabled repeatable distinction of 5 types of architectural hip deformities. [37] (10.1007/s00402-019-03298-1)
• [L4] This study revealed activity dependent kinematics of healthy hip joints with coordinated pelvic and femoral dynamic movements. [38] (10.1155/2014/457573)
• [L5] Subject-specific gait combined with inverse dynamic analysis provides pre-processing parameters for FE simulation to enable more accurate biomechanical analysis of the hip joint. [39] (10.1186/s13018-022-03094-5)
• [L5] The acetabular labrum bears a direct mechanical role during hip motion, thus resecting the hip's labrum during surgery might be detrimental for hip joint's biomechanics as it might modify strains distribution between the acetabulum and femur. [40] (10.1007/s00167-017-4524-8)
• [L4] A normative database of hip and knee kinematics utilized by football athletes was developed. [41] (10.1177/2325967114534591)
• [L5] Hip abductor moment arm varies substantially throughout the hip's range of motion in the coronal plane. [42] (10.1186/1749-799x-6-6)
• [L5] The distinctive phase-dependent biomechanical response of the hip demonstrated its coordinated control strategy for balance recovery due to gait perturbations. [43] (10.1186/s12891-023-06897-7)
• [L4] Current analysis revealed trends that degenerative hips experience more abnormal hip kinematics that leads to higher articulating surface forces and stresses within the acetabulum. [44] (10.1016/j.arth.2019.08.057)
• [L3] Abnormal hip kinematics in women with patellofemoral pain appears to be the result of diminished hip-muscle performance as opposed to altered femoral structure. [45] (10.1177/0363546508326711)
• [L4] A thorough appreciation of the anatomy of the abductor musculature, specific clinical signs and imaging findings will lead to an appropriate diagnosis being made and management plan instituted. [46] (10.1007/s00167-020-06354-1)
• [L5] A six degree-of-freedom robot is appropriate to reproduce the physiological range of motion of the hip joint. [47] (10.1186/s13018-023-03601-2)
• [L4] This study is the first to map the hip center of rotation trajectory under common movements in a large cohort, highlighting the importance of hip translation on physiologic range of motion. [48] (10.1177/2325967124s00166)
• [L4] Additionally, patients reported significant improvement in function and pain at 1 year postoperatively, but these improvements did not correlate with improvements in hip kinematics. [49] (10.1177/23259671251339777)
• [L3] The smartphone application is one of the practical measurements in hip rotational angles. [50] (10.1186/s12891-021-03995-2)
• [L5] Despite simulating lower degrees of hip flexion and internal rotation, increased stress and a shift in contact location were observed in the simulated models of FAI. [51] (10.1016/j.arthro.2017.03.018)
• [L5] The proper diagnosis and treatment of patients with concurrent hip and spine pathological processes can present a substantial challenge due to overlapping symptomatology and no consensus on which condition to address first. [52] (10.2106/jbjs.20.01728)
• [L5] The planning of surgical procedures may be improved by the proposed classification. [53] (10.1007/s00167-018-5318-3)
• [L4] Geometric measurements are reliably interpreted and may be useful as a further measurement of quality, while morphological features are generally poorly interpreted but improve with simpler binary classification. [55] (10.1302/0301-620x.105b10.bjj-2023-0143.r1)
• [L1] Females had more profound symptomatology and milder morphologic abnormalities, while males had a higher activity level, larger morphologic abnormalities, more common combined-type FAI morphologies, and more extensive intra-articular disease. [56] (10.2106/jbjs.m.01320)
• [L4] The classification developed allows for appropriate grouping and comparison of distinct CS implants. [57] (10.1016/j.arth.2025.05.039)
• [L4] This classification system allows for the ability to evaluate differing repair patterns and their effects on postoperative clinical outcomes. [58] (10.1177/2325967125s00101)
• [L3] The greater trochanter classification system based on the anatomy and biomechanics could distinguish various types of DDH and aid in making surgical strategies. [59] (10.1016/j.arth.2025.08.013)
• [L4] The classification of developmental patterns illustrates the varying directional changes that can occur in lower-extremity length discrepancies and their dependence on underlying biological phenomena. [60] (10.2106/00004623-198264050-00001)
• [L4] Several consistent anatomical levels were identified for single axial MR slice to facilitate muscle size and fatty infiltration muscle measures at the hip, providing the basis for reliable and accurate data synthesis and improvements in the validity of future between studies analyses. [61] (10.1186/s12891-022-05439-x)
• [L3] CT was found to have higher interobserver reliability than MRI, and diagnosis should not rely exclusively on either examination or radiologic criteria. [62] (10.1016/j.arthro.2011.10.021)
• [L3] The method was feasible with routine MRI and a short image acquisition time. [63] (10.1177/23259671251334138)
• [L2] Type II and III sourcil types account for the majority, to which the modified approach is better. [64] (10.1016/j.arthro.2023.11.024)
• [L5] Specifically, the variability and elongated morphology of the ME differentiated this landmark from the AT and GT, which demonstrated the most consistent morphology. [65] (10.1016/j.asmr.2022.09.003)
• [Paper] MRI scanning is necessary to establish whether some patients have an occult fracture. [66] (10.1016/j.injury.2007.04.023)
• [L3] The clinical relevance of this study is that capsular thickness and intra-substance changes of the anterior capsule vary which could alter capsular management strategies. [67] (10.1007/s00167-022-07022-2)
• [L5] Based on data showing that standard MRI scans cannot replicate the appropriate level of detail for AIIS morphology classification compared to 3D CT, the author concludes that the preoperative planning CT scan should not be eliminated from the patient pathway, although future refinements in 3D MRI techniques may eventually allow them to replace low-dose 3D CT scans. [68] (10.1016/j.arthro.2021.08.012)
• [Paper] This MRI documentation should be established as a standard examination post-reduction. [69] (10.1007/s00402-003-0518-8)
• [L4] A precise knowledge of anatomy and clear goals in the surgical approach can minimize complications and facilitate visualization and instrumentation placement in the direct anterior approach to the hip joint. [70] (10.1186/s12891-023-06254-8)
• [L1] The range of knee anatomy in patients scheduled for TKA is wide. [71] (10.1016/j.arth.2017.02.028)
• [L2] On the basis of these excellent results, the authors intend to change their clinical practice to use MRI-based 3D models for future clinical practice instead of CT-based 3D models. [72] (10.1177/0363546519869681)
• [L4] Surgical treatment limited to localized recontouring of the head-neck profile may fail to address significant components of the underlying abnormality. [73] (10.1016/j.arth.2011.04.028)
• [Case_report] Magnetic resonance imaging is effective in localizing this type of lesion. [74] (10.2106/00004623-198971090-00022)
• [L4] Imaging for osteonecrosis is recommended, with evidence suggesting 4- to 6-week magnetic resonance imaging and follow-up at 3 months for those with suspicious findings in the femoral head. [75] (10.1177/03635465211036104)
• [L3] There were substantial improvements in patient-reported outcomes, showing acceptable midterm clinical healing rates and low reoperation/failure rates. [76] (10.1016/j.arthro.2020.12.150)
• [L3] Despite improvements in clinical outcomes and bony histology, there were no difference detected in the progression of medial compartment post-traumatic gonarthrosis between groups. [77] (10.1016/j.arthro.2017.08.096)
• [L4] Computed tomography provides a noninvasive method for studying anatomy in live subjects, allowing for the detailed mapping of position, size, and orientation of the abductor muscles of the hip. [79] (10.2106/00004623-198769070-00010)
• [L4] Experience is currently insufficient to establish exact criteria, but the method helps confirm adequacy of coverage and guides surgical decision-making. [80] (10.2106/00004623-198163020-00016)
• [L5] Anatomic ALL reconstruction did not reduce anterolateral rotational laxity. [81] (10.1177/2325967116s00027)
• [L4] Pathologic changes seen on MRI were symptomatic in less than two thirds of the dancers. [82] (10.1016/j.arthro.2012.10.012)
• [L3] However, ioMRI cannot yet replace CT scans for thorough evaluation, though it may be considered when CT is contraindicated. [83] (10.1177/2325967125s00090)
• [L5] Most patients tend to resolve GTPS or lateral hip pain with non-surgical management in the mid-term but when everything failed, surgical options should be evaluated. [84] (10.1007/s00167-020-06366-x)
• [L2] Operative management of fragility fractures of the pelvis should be considered for patients failing a brief period of non-operative management, however prospective randomised trials need to be performed to provide improved evidence for this intervention. [85] (10.1186/s12891-021-04579-w)
• [L5] Biomechanical and long-term clinical studies will continue to be performed to better understand the importance of the labrum and how to restore its function. [86] (10.1016/j.arthro.2010.12.004)
• [L3] Measurements of femoral version on CT strongly correlated with those on MRI. [87] (10.5435/jaaos-d-25-01274)
• [L4] When nonoperative treatment fails, the PROs in these patients after operative management are comparable with those in patients with osseous cam lesions. [88] (10.1177/03635465231206815)
• [L4] With an average follow-up time of 12 months, all clinical and functional results as well as activity and quality of life improved statistically. [89] (10.1016/j.arthro.2013.09.021)
• [L5] Although a demanding technique with a high rate of related complications, once anatomic reconstruction of the hip is achieved, patients have a remarkably good functional capacity and implant survival during long follow-up periods. [90] (10.1302/2058-5241.1.000026)
• [L3] Treatment strategies may need to be adjusted to preserve long-term function. [91] (10.2106/jbjs.25.01271)
• [L5] Surgical management is indicated for progressive, painful, unilateral deformity or leg-length discrepancy, while moderate nonprogressive deformity often does not require surgery. [92] (10.5435/00124635-199803000-00003)
• [L4] Non-operative management is associated with highly variable periods of convalescence, poor return to preinjury level of function and high risk of injury recurrence. [93] (10.1302/2058-5241.5.200055)
• [L2] Current evidence suggests that modular BKA provides comparable functional outcome to TKA at short-term to midterm follow-up, however, with poor long-term survivorship. [94] (10.1016/j.arth.2019.09.042)
• [L5] In non-elite patients, persistent grade 2 or 3 laxity beyond 12 weeks should prompt combined anterior cruciate ligament reconstruction with MCL repair and reconstruction. [95] (10.1002/arj.70105)
• [L5] Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up. [96] (10.1186/1749-799x-2-10)
• [L4] Non-operative treatments are usually ineffective, and while rotational osteotomies are effective, they are associated with significant complication rates. [97] (10.2106/00004623-198567050-00027)
• [L5] The study emphasizes that anatomic femoral attachment is critical to a well-functioning reconstruction and minimizes complications, while nonanatomic placement can cause significant changes in graft isometry. [99] (10.1177/2325967115569198)
• [L5] The use of the medial portals did not cause any damage to the neurovascular structures evaluated. [100] (10.1016/j.arthro.2013.09.004)
• [L5] Recognition of femoroacetabular impingement and early intervention before the degenerative process is advanced is likely to have a considerable impact on the natural history of the disease, delaying the onset of end-stage arthritis in young patients. [101] (10.1016/j.arth.2007.05.039)
• [L4] The natural history is often favorable for children younger than 6 years and poor for children older than 8 to 10 years. [102] (10.5435/jaaos-d-24-01469)
• [L3] The study aimed to determine the long-term objective and subjective outcome of untreated articular cartilage defects observed at the time of ACL reconstruction. [103] (10.1016/j.arthro.2014.04.071)
• [L4] The sixty-five variant hips were not significantly different from normal joints in linear measurements, suggesting they are examples of morphological variability within the range of normal development rather than deformities. [104] (10.2106/00004623-198062070-00004)
• [L3] Specific morphological characteristics on pelvis radiographs of AVN hips were predictive for poor outcome, at a very young age. [105] (10.1302/0301-620x.103b5.bjj-2020-1485.r1)

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[84] Non‐surgical treatment as the first step to manage peritrochanteric space disorders. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06366-x

[85] Operative management of fragility fractures of the pelvis – a systematic review. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04579-w

[86] Comments on “Labral Base Refixation in the Hip: Rationale and Technique for an Anatomic Approach to Labral Repair”. Arthroscopy. 2011. DOI: 10.1016/j.arthro.2010.12.004

[87] The Relationship Between Prone Range of Motion and Measured Femoral Version on Advanced Imaging in Adolescent Patients. Journal of the American Academy of Orthopaedic Surgeons. 2026. DOI: 10.5435/jaaos-d-25-01274

[88] Soft Tissue Cam Impingement in Adolescents: MRI Reveals Impingement Lesions Underappreciated on Radiographs. The American Journal of Sports Medicine. 2023. DOI: 10.1177/03635465231206815

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[91] Thigh Muscle Changes at Long-Term Evaluation Following ACL Injury Differ from Early Changes Associated with ACL Injury and Reconstruction. Journal of Bone and Joint Surgery. 2026. DOI: 10.2106/jbjs.25.01271

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[102] Legg-Calvé-Perthes Disease. Journal of the American Academy of Orthopaedic Surgeons. 2025. DOI: 10.5435/jaaos-d-24-01469

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