Anatomy

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

Overview

Successful knee surgery relies on a deep anatomical and functional understanding to restore individual patient anatomy rather than surgical technique alone [76]. Comprehensive knowledge of regional anatomy is essential for safe and effective procedures, including aspiration and injection of the lower extremity [12]. While the range of knee anatomy in patients scheduled for total knee arthroplasty is wide [70], existing techniques based on standard assumptions may fail to address morphologic outliers, potentially leading to dissatisfaction [57].

Procedural indications and outcomes vary significantly by technique and implant design. Total knee arthroplasty using hinge joints depends on implant design, appropriate technical use, and adequate indications [14], whereas unicompartmental and bicompartmental arthroplasty with finned metal tibial-plateau implants has a defined role in reconstructive surgery with proper indications [18]. Advanced microfracture techniques for isolated patellar chondral defects show promise, though indications and technique variability require elucidation in higher-level studies [11]. Newer surgical techniques should not be assumed superior to older ones without sufficient outcome evaluation [76].

Specific anatomical considerations dictate procedural caution and selection. Anatomic anterolateral ligament reconstruction leads to overconstraint at any fixation angle and should be used with caution pending further investigation [19]. Trochleoplasty is indicated as a primary procedure with clear indications rather than as a secondary or revision procedure [20]. Around-the-knee osteotomies correct coronal, sagittal, and axial plane deformities [63], while thorough anatomical knowledge is imperative to manage cortical blowout during anterior cruciate ligament reconstruction [66]. Both open and arthroscopic biceps tenodesis provide satisfactory outcomes with no identifiable differences, allowing surgeon preference to dictate technique selection [90]. Wide variations in tibial slopes and trochlear angles exist in the arthritic knee [57].

Anatomy & Pathophysiology

Osseous Morphology and Alignment

Knee alignment is dynamic, varying between individuals and changing with different postures [54]. The morphology of the proximal femur correlates strongly with the geometry of the distal femoral trochlea, serving as a factor of clinical importance for understanding physiological kinematics and refining kinematic knee replacement concepts [55]. Three-dimensional analysis of the sagittal curvature of the femoral trochlea in specific populations may further enhance the understanding of knee kinematics and the development of physiological knee prostheses [51]. Functional knee phenotypes better represent the variability of coronal knee alignment than conventional valgus, varus, or neutral systems, with osteoarthritic knees demonstrating significant variability that necessitates a personalized approach to total knee arthroplasty (TKA) [95, 101]. The primary challenge lies in identifying the optimal alignment strategy for each functional knee phenotype [101].

Ligamentous Anatomy and Biomechanics

Comprehensive reviews detail the bone structure, vascular and nerve supply, ligamentous organization, and functional mechanics relevant to stability and injury [62]. Anatomically and radiographically, the bone attachments of the medial collateral and posterior oblique ligaments are defined, facilitating repairs that restore physiological laxity and stability patterns across the arc of knee flexion [99]. Biomechanical studies determine the magnitude and direction of forces and moments in diarthrodial joints to assist clinicians in assessing function and planning treatment [87]. Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six-degree-of-freedom knee kinematics [56]. While double-bundle reconstructions may better restore normal knee kinematics than single-bundle reconstructions, clinical outcomes have not revealed a difference between the two [102]. Isometric grafts restore normal knee kinematics regardless of the flexion angle at which they are secured [81]. In pediatric populations, neither all-epiphyseal nor over-the-top reconstruction techniques restored the contact mechanics and kinematics of an ACL-intact knee [47]. In high-grade multiligamentous knee injuries, failure to treat all injured structures leads to altered knee kinematics and poorer outcomes [78]. Regarding anchor versus knotless tunnel repair, no statistically significant differences were found regarding the restoration of knee kinematics, mean failure loads, or stiffness [58].

Kinematics and Functional Analysis

Standardized testing protocols are proposed to characterize the biomechanical behavior of the knee and cruciate ligaments to allow comparisons between investigations [50]. Comparative anatomical studies suggest that understanding shared kinematic principles can improve the design of external bracing systems and total knee replacements [96]. In kneeling, a difference exists in rotational kinematics between the flexion phase and the extension phase [45]. A knee joint simulator successfully demonstrated the anatomy, physiology, and kinematics of knee ligaments, allowed teaching of ligamentous instability tests, and demonstrated the effect of knee ligament reconstructive surgery [91]. Proposed methods using gait and fluoroscopic analysis can evaluate knee joint mechanical parameters such as stress distribution at the joint contact interface [84]. Individualization of knee arthroplasty based on patient anatomy, physiology, and kinematics represents the future direction of care [75].

Classification

3D Knee Anatomy Phenotyping: Three-dimensional imaging facilitates superior anatomical understanding of the posteromedial corner [1]. CT-based phenotyping establishes a 3D classification of arthritic knee anatomy into four foundational morphologies, where Types 1 and 3 represent outliers present in 26% of knees undergoing total knee arthroplasty [80].

Anterior Cruciate Ligament (ACL) Insertion: The topographical alignment of the separate bundles of the human ACL stump's tibial insertion footprint varies across a very wide range [13]. Consequently, historical anteromedial and posterolateral terminology for the ACL bundles should not be used routinely [13]. A classification system for the shape of the tibial insertion site is a repeatable and reliable tool [44]. Consideration of the individual shape of the tibial insertion site is required to prevent iatrogenic damage and ensure proper footprint restoration [44].

Medial Knee Structures: An anatomic study delineated a consistent three-layered anatomical pattern of the medial knee [53]. Specific nomenclature for the superficial medial ligament and posteromedial capsule should be used rather than the term 'posterior oblique ligament' based on this consistent three-layered pattern [53].

Anterolateral Ligament (ALL): An anatomic study identified two structures of the knee ALL, described as the superficial and deep ALL, which were consistent with previous but conflicting descriptions [15].

Medial Meniscus: A classification system for medial meniscus ramp tears allows for the evaluation of differing repair patterns and their effects on postoperative clinical outcomes [48].

Pes Anserinus: The proposed classification of pes anserinus morphology may improve the planning of surgical procedures [52].

Medial Patellofemoral Ligament (MPFL): The MPFL must be reconstructed as anatomically as possible in its insertion and in its shape given the importance of this structure [67].

Developmental Patterns: The classification of developmental patterns in lower-extremity length discrepancies illustrates the varying directional changes that can occur and their dependence on underlying biological phenomena [61].

Anatomic Variants: Anatomic variants with a posterior tibial slope (PTS) ≥12° were very uncommon (≤3%) and could be considered pathological [6]. An aberrant branch of the long head of the biceps tendon represents an anatomic variant that has not been previously described [8].

Other Considerations: The algorithm for 3D surface reconstruction of the femur and tibia from parallel 2D contours can be used for the 3D reconstruction of other types of 2D cuts [89]. Special attention must be paid to branches when using this algorithm, as the proposed algorithm is not designed for complex branching structures [89].

Clinical Presentation

A comprehensive understanding of knee anatomy, including three-dimensional imaging of the posteromedial corner, is essential for the appropriate management of pathologies and injuries [1, 4, 5]. This knowledge base facilitates the identification of characteristic MR features that aid radiologists in diagnosing disorders causing anterior knee pain [7]. Furthermore, recognizing anatomic variants is critical; for instance, posterior tibial slope (PTS) ≥12° is uncommon (≤3%) and likely pathological [6], while an aberrant branch of the long head of the biceps tendon represents a previously undescribed variant [8].

Diagnostic Modalities: Accurate diagnosis relies on specific imaging and examination techniques. Idiopathic osteonecrosis of the patella is confirmed via radiographs, radioisotopic bone scan, conventional tomograms, and histological examination after excision [9]. Ultrasound localizes nerve lesions in fibular neuropathy at the knee and characterizes them morphologically to improve therapeutic decision-making [30]. Distinct malformations in nail patella syndrome are recognizable on conventional radiographs, guiding the interpretation of aberrant morphology [34]. Additionally, a new symptomatic intra-articular cord-like structure associated with discoid meniscus serves as an important differential diagnosis for symptoms typically attributed to meniscus pathology [29].

Anatomic Variants and Clinical Impact: Several anomalies present diagnostic challenges or require specific surgical considerations. Knowledge of the prevalence, size, shape, and location of the semimembranosus-tibial collateral ligament bursa aids in the differential diagnosis of medial knee pain [33]. Instability of the proximal tibiofibular joint is often missed; understanding its etiology and anatomic variations is essential for evaluating symptomatic patients [31]. The presence of an aberrant anterior tibial artery does not depend on the patient's morphotype, though its lumen diameter is highly variable and its clinical impact remains undetermined [32]. While the anterolateral ligament of the human knee is consistently present [43], the anterior meniscofemoral ligament of the medial meniscus is an anomaly usually asymptomatic and should not be routinely excised [39]. Other rare anomalies, such as those at the proximal musculotendinous junction of the adductor longus muscle, may explain difficulties in localizing injury sites [40], whereas an anomalous flexor carpi radialis brevis muscle appears asymptomatic [41].

Specific Syndromes: Distinct clinical syndromes are associated with specific anatomical lesions. An unusual gastrocnemius muscle syndrome represents a definite clinical entity amenable to surgical repair [36]. Conversely, anomalies of the flexor digitorum superficialis are rare and can present a diagnostic dilemma [38].

Investigations

Plain radiography: Plain radiographs serve as the appropriate initial imaging study for most knee conditions [42]. They allow for the precise and reproducible definition of medial meniscus horn position [72] and the delineation of posterolateral rim morphology, where type 1 rims correlate with distinct anatomic morphology and type 2 rims with indistinct morphology [73]. Radiographs are also sufficient for assessing bone morphology to visually evaluate the effect of tibial plateau morphology on the joint line convergence angle in medial open wedge high tibial osteotomy [82]. Comprehensive qualitative and quantitative guidelines exist for assessing posterolateral knee structures on both anteroposterior and lateral views [93]. Furthermore, reliable skeletal maturity estimation systems utilizing routine knee radiographs are described for surgical planning without requiring additional hand radiographs [103].

MRI: Magnetic resonance imaging is the recommended routine method for accurately diagnosing and treating bone stress injuries causing exercise-induced knee pain [35] and is the technique of choice for identifying complete supra-patellar plica, though limitations persist [46]. MRI is crucial for operative planning and distinguishing benign from malignant soft-tissue tumors, such as ganglia of the superior tibiofibular joint [92]. It is recommended to routinely review the integrity of the Kaplan fibers on MRI scans [74] and provides more reliable predictions of ACL length than radiographs [98]. While MRI can identify anterior lateral ligament (ALL) injury with good agreement on routine 1.5T scans, it lacks accuracy in differentiating complete from partial ALL tears [94]. Anatomical, MRI-based parameters, including increased tibial tubercle-trochlear groove distance and patellar height, indicate a higher risk of recurrent patellar dislocation following medial reefing [71]. Three-dimensional images derived from MRI help better understand the anatomy of the posteromedial corner of the knee [1]. Additionally, MR imaging presents characteristic features of common and uncommon disorders causing anterior knee pain to aid in accurate diagnosis [7]. However, selective MRI does not provide enhanced diagnostic utility over clinical examination in children and adolescents, particularly when the clinical diagnosis is uncertain and MRI input will alter the treatment plan [79].

CT: Advanced imaging such as CT provides enhanced detail for specific soft tissue, bone, and implant assessments [42].

Bone scan: A radioisotopic bone scan is one of the modalities used to confirm the diagnosis of idiopathic osteonecrosis of the patella, alongside radiographs, conventional tomograms, and histological examination after excision [9].

Other Considerations: A thorough understanding of anatomy, physical examination findings, and imaging characteristics aids in the management of posteromedial corner injuries [4]. Advanced imaging should be used to augment a history and examination when necessary but should not replace a thorough history and physical examination [16]. Most commonly utilized radiographic measures for the elbow are consistent between sexes, across the adolescent age group, and between adolescents and young adults [64].

Treatment

Non-Operative

Conservative management serves as the primary intervention for specific pathologies, including apophysitis of the proximal patella [68], anomalous insertion of the medial meniscus horns in young, skeletally immature patients with mild symptoms [100], and moderate nonprogressive coxa vara in childhood [107]. Non-operative approaches are also indicated for partial ruptures of the lateral collateral ligament occurring with complete anterolateral ligament ruptures, which yield excellent outcomes regarding return to sport [111]. However, non-operative treatments for lower-extremity rotational problems in children are generally ineffective [69], and non-operative management of proximal rectus femoris avulsion injuries is associated with poor return to preinjury function, high recurrence risk, and highly variable convalescence [105]. While many non-operative modalities exist for atraumatic meniscus tears, operative intervention may be necessary to improve pain and prevent progression to osteoarthritis [112].

Operative

Indications: Surgical intervention is indicated for coxa vara in childhood when deformity is progressive, painful, unilateral, or associated with leg-length discrepancy [107]. Surgery is also indicated for the surgical release of the vastus medialis muscle when nonoperative treatment fails [104] and for surgical correction of a subluxating biceps femoris tendon if symptoms are unresponsive to conservative care [110]. Intraosseous bioplasty should be considered for subchondral cysts in patients where conservative management fails to ameliorate symptoms [108]. For non-elite patients, persistent grade 2 or 3 MCL laxity beyond 12 weeks in the setting of ACL rupture warrants combined ACL reconstruction with MCL repair and reconstruction [113]. Surgical management is appropriate for congenital femoral deficiency when treated by clinicians with considerable deformity experience to maximize functional outcomes [77].

Surgical Approach / Technique: Anatomical anterior cruciate ligament reconstruction results in fewer rates of atraumatic graft rupture and higher rates of rotatory knee stability compared to non-anatomical approaches, though the overall failure rate is similar between the two [49]. Anatomic anterolateral ligament reconstruction leads to overconstraint at any fixation angle; therefore, the technique and indications require further investigation, and the procedure is recommended for use with caution [19]. Trochleoplasty should be performed as a primary procedure with clear indications rather than as a secondary or revision procedure [20]. Comprehensive knowledge of regional anatomy is essential for safe and effective aspiration and injection of the lower extremity [12]. Advanced microfracture techniques for isolated patellar chondral defects show promise, though indications and variability require elucidation in higher-level studies [11]. Repair of horizontal cleavage meniscus tears demonstrates substantial improvements in patient-reported outcomes, acceptable midterm healing rates, and low reoperation rates [59]. Debridement of mucoid tissue is a safe and effective treatment for mucoid degeneration of the posterior cruciate ligament [60]. Current approaches for acute multiligamentary knee injuries favor surgical intervention, specialized techniques, and early rehabilitation, with a better understanding of treatment factors improving functional results [88].

Implant Selection: Total knee arthroplasty using hinge joints generally depends on implant design, appropriate technical use, and adequate indications [14]. Unicompartmental and bicompartmental arthroplasty with a finned metal tibial-plateau implant has a place in reconstructive surgery of the arthritic knee joint with proper indications [18]. Single soft tissue graft reconstruction of the fibular collateral ligament and posterolateral corner demonstrated satisfactory clinical and functional outcomes [85]. Nonorthotopic osteochondral allografts are an acceptable practice that can reliably restore the articular surface within a suitable range, though further clinical investigation is necessary to determine long-term effects on survivorship and outcomes [2]. Outcomes of osteochondral allograft transplantation in "ideal" candidates were equal or superior to other cartilage repair techniques [86].

Alignment / Balancing Strategy: Conventional non-anatomic ACL reconstruction techniques do not prevent early osteoarthritis or restore normal dynamic knee function, suggesting that restoring anatomy may be the key to success, though high-quality prospective randomized trials are needed to validate benefits [83].

Adjuncts: The heterogeneity of treatment and outcomes for avulsions of the distal femur and proximal tibia in children and adolescents highlights the importance of developing an algorithmic approach to diagnosis and treatment [65].

Other Considerations: MPFL reconstruction provides satisfactory midterm clinical results and a low incidence of patellofemoral arthritis in patients with low-grade trochlear dysplasia [3].

Complications

Other Considerations: Nonorthotopic osteochondral allografts can reliably restore the articular surface within a suitable range, though long-term effects on graft survivorship and clinical outcomes require further investigation [2]. Midterm follow-up of MPFL reconstruction for patellar instability in patients with low-grade trochlear dysplasia shows satisfactory outcomes without remarkable arthritic changes [3]. Femoral component coronal alignment in fixed-bearing unicompartmental knee arthroplasty may affect long-term clinical outcomes but does not affect short-term clinical outcomes or 10-year survivorship [17]. Computer navigated lateral opening wedge distal femoral osteotomy demonstrates satisfactory clinical outcomes and 79% survivorship in long-term follow-up [21]. Adding cartilage restoration procedures to high tibial osteotomy has failed to show improved clinical outcomes in the short term in most studies [109]. Exaggerated physiological deformities at the knee may correct spontaneously and should not be stapled before the skeletal age of eleven in girls and twelve in boys [117].

Instability: The topographical alignment of the separate bundles of the human anterior cruciate ligament stump's tibial insertion footprint varies over a very wide range [13]. Consequently, the historical anteromedial and posterolateral terminology for the anterior cruciate ligament bundles should not be used routinely due to varied topographical alignment [13]. Bone microstructure from anterior cruciate ligament footprints is similar after ligament reconstruction and does not affect long-term stability of the operated knee joint [22]. Furthermore, bone microstructure from anterior cruciate ligament footprints is not dependent on the time from injury to surgery [22]. The heterogeneity of pathology treated, follow-up time, and outcome measures in high tibial osteotomy for knee instability limits comparison between studies [25].

Other Considerations: Anatomical studies identify two structures of the knee anterolateral ligament described as superficial and deep, consistent with previous but conflicting descriptions [15]. Early aggressive treatment and long-term follow-up are mandatory for metastasis of adamantinoma after knee disarticulation [24]. Synovial membrane and synovial fluid disease evolution progresses from slight activity and vascularization in early stages to marked fibrosis, multistratified intima, and vascular proliferation in chronic cases [27]. Myositis ossificans in the newborn can undergo extensive remodeling with almost normal bone morphology at follow-up despite an atypical anatomical site and rapid course [28]. Cam morphology exists in historical populations at rates comparable with contemporary populations [115].

Recovery

Light activity (weeks): Evidence does not specify a discrete week range for light activity or return to desk work across the provided studies. However, short-term clinical outcomes in fixed-bearing unicompartmental knee arthroplasty are unaffected by femoral component coronal alignment, suggesting early functional stability [17]. Similarly, MPFL reconstruction for patellar instability in patients with low-grade trochlear dysplasia yields satisfactory midterm clinical results, implying a return to light activities within the midterm timeframe [3].

Full activity (months): Long-term follow-up is required to define the timeline for full activity return in several contexts. Autologous Matrix-Induced Chondrogenesis for focal cartilage defects requires further long-term studies to determine if the grafted area maintains structural and functional integrity [10]. Computer navigated lateral opening wedge distal femoral osteotomy for lateral compartment knee arthrosis demonstrates 79% survivorship in long-term follow-up [21]. For anterior cruciate ligament reconstruction, further studies are needed to understand if the two-incision technique for femoral tunnel placement can ameliorate proprioception and clinical outcomes at long-term follow-up [97].

Complete recovery / outcome plateau (months): The timeline for complete recovery and outcome stabilization varies by pathology. Nonorthotopic osteochondral allografts require further investigation regarding long-term effects on graft survivorship and clinical outcomes [2]. A complete ACL lesion shows favorable initial evolution at 30 months but has a re-rupture rate or 'scar tissue' rupture of 40% at a mean follow-up of 8 years [122]. Femoral component coronal alignment in fixed-bearing unicompartmental knee arthroplasty does not affect 10-year survivorship [17]. The prognosis after excision of localized pigmented villonodular synovitis of the knee is excellent, with no recurrences observed in the series [121].

Rehabilitation protocol: The provided evidence does not contain specific details regarding PT phasing, immobilisation duration, weight-bearing progression, or brace removal timing.

Functional milestones: Clinical outcomes of open wedge high tibial osteotomy are affected by cartilage status rather than by chronologic age [123]. The presence of chondrosis at the time of surgery is an important prognosticator of functional outcome at intermediate follow-up in late multiple ligament and posterolateral corner-reconstructed knees [106]. Bone microstructure from anterior cruciate ligament footprints has no impact on the long-term stability of the operated knee joint [22]. MPFL reconstruction for patellar instability in patients with low-grade trochlear dysplasia is associated with a low incidence of patellofemoral arthritis at midterm follow-up [3].

Other Considerations: More trials and long-term evidence are needed regarding anterior knee pain and patellofemoral osteoarthritis [23]. Heterogeneity of pathology treated, follow-up time, and outcome measures limit comparison between studies on high tibial osteotomy for knee instability [25]. Early aggressive treatment and long-term follow-up are mandatory for metastasis of adamantinoma after knee disarticulation [24]. The natural course of chronic exertional compartment syndrome of the lower leg seems to be persistent symptoms over time [118]. Paget's disease of the tibia showed faster longitudinal growth during the first six years before slowing as the disease extended to involve the entire bone [119]. The prognosis for spontaneous recovery without specific treatment is relatively good in most instances of the condition described by Snedecor and Wilson, though permanent epiphyseal growth changes may occur occasionally [120]. Bone microstructure from anterior cruciate ligament footprints is similar after ligament reconstruction and is not dependent on the time from injury to surgery [22]. The lesion in myositis ossificans in the newborn underwent extensive remodeling with almost normal bone morphology at follow-up despite an atypical anatomical site and rapid course [28].

Key Evidence

• [L5] Three-dimensional images of these structures can help better understanding its anatomy. (10.1007/s00167-011-1615-9)
• [L5] The use of nonorthotopic osteochondral allografts is an acceptable practice that can reliably restore the articular surface within a suitable range, though further clinical investigation is necessary to determine long-term effects on graft survivorship and clinical outcomes. (10.1016/j.arthro.2018.08.009)
• [L3] It provides satisfactory outcomes without remarkable arthritic changes at a mid term follow-up. (10.1002/ksa.70101)
• [L5] A thorough understanding of the anatomy, physical examination findings, and imaging characteristics will aid the physician in the management of these injuries. (10.5435/jaaos-d-16-00020)
• [L5] A knowledge base of the anatomy and function is essential to treat all different pathologies appropriately. (10.1007/s00167-005-0683-0)
• [L3] Anatomic variants with a PTS ≥12° were very uncommon (≤3%) and could be considered pathological. (10.1177/2325967119895258)
• [L4] This pictorial essay presents the characteristic MR features of common and uncommon disorders causing anterior knee pain to aid radiologists in identifying typical imaging patterns for accurate diagnosis and appropriate therapy. (10.1007/s00167-012-1976-8)
• [L4] The anomaly represents an anatomic variant that has not been previously described. (10.1016/j.jse.2011.01.036)
• [L4] However, further studies with long-term follow-up are needed to determine whether the grafted area will maintain structural and functional integrity over time. (10.1007/s00167-010-1042-3)
• [L4] Advanced microfracture techniques showed promise, but indications and variability in techniques need to be elucidated in higher-level studies. (10.1177/23259671231153422)
• [L5] Comprehensive knowledge of regional anatomy, procedural indications, and appropriate techniques are essential for safe and effective aspiration and injection. (10.5435/jaaos-d-16-00762)
• [L5] The topographical alignment of the separate bundles is varied on a very wide range, suggesting that the historical anteromedial and posterolateral terminology should not be used routinely. (10.1007/s00167-008-0552-8)
• [L4] Clinical results generally depend on implant design, appropriate technical use, and adequate indications. (10.1302/2058-5241.4.180056)
• [L5] This anatomic study clearly identified 2 structures, described as the superficial and deep ALL, which were consistent with previous but conflicting descriptions of the ALL. (10.1177/2325967116675604)
• [L5] Advanced imaging should be used to augment a history and examination when necessary but should not replace a thorough history and physical examination. (10.5435/jaaos-d-15-00463)
• [L3] Femoral component coronal alignment may affect long-term clinical outcomes, but not short-term clinical outcomes nor 10-year survivorship. (10.1016/j.arth.2020.07.070)
• [L4] The results suggest that with the proper indications this arthroplasty has a place in reconstructive surgery of the arthritic knee joint. (10.2106/00004623-198567080-00005)
• [L5] The surgical technique and indications for this procedure should be investigated further and it is recommended that ALLR be used with caution. (10.1177/2325967116s00166)
• [L5] Trochleoplasty should not be performed as a secondary or revision procedure but rather as a primary procedure with clear indications. (10.1016/j.arthro.2020.05.050)
• [L4] Computer navigated DFLOWO has satisfactory clinical outcomes and 79% survivorship in long-term follow-up. (10.1177/2325967120s00527)
• [L2] The bone microstructure is not dependent on the time from injury to surgery and has no impact on the long-term stability of the operated knee joint. (10.1007/s00167-021-06493-z)
• [L5] More trials and long-term evidence are needed. (10.1136/jisakos-2016-000106)
• [L4] Early aggressive treatment and long-term follow-up are mandatory. (10.2106/00004623-198668050-00023)
• [L4] The heterogeneity of the pathology treated, follow-up time, and outcome measures limit comparison between studies. (10.1177/2325967116633419)
• [L4] It describes histological evolution from slight activity and vascularization in early stages to marked fibrosis, multistratified intima, and vascular proliferation in chronic cases. (10.2106/00004623-196446040-00026)
• [Case_report] Despite the atypical anatomical site and rapid course, the lesion underwent extensive remodeling with almost normal bone morphology at follow-up. (10.2106/00004623-198668030-00023)
• [L4] This ligamentous structure is an important differential diagnosis to symptoms usually referred to as meniscus pathology. (10.1016/j.arthro.2005.12.023)
• [Case_report] Ultrasound is able to localize the site of nerve lesion and characterize it from a morphological point of view, adding information about nerve involvement to improve diagnostic ability and therapeutic decision-making. (10.1007/s00167-017-4601-z)
• [L5] Instability of the proximal tibiofibular joint is rarely reported and often missed; understanding its etiology, symptoms, and anatomic variations is essential for evaluating symptomatic patients. (10.5435/00124635-200303000-00006)
• [L3] The patient's morphotype did not influence its presence, the lumen diameter is highly variable and its clinical impact has yet to be determined. (10.1002/ksa.12435)
• [L5] Knowledge of its prevalence, size, shape, and location aids in the differential diagnosis of medial knee pain. (10.2106/00004623-199409000-00007)
• [L4] These distinct malformations are easily recognisable on conventional radiographs and lead to the correct interpretation of the aberrant morphology essential in treatment. (10.1302/0301-620x.98b4.37025)
• [L4] Magnetic resonance imaging is recommended as a routine imaging method for accurate diagnosis and appropriate treatment. (10.1177/0363546505278699)
• [L4] The case represents a definite clinical syndrome associated with a specific anatomical lesion that is amenable to surgical repair. (10.2106/00004623-197355060-00016)
• [L4] Anomalies of the flexor digitorum superficialis are rare and can present a diagnostic dilemma; this article summarizes previously reported anomalies, reports a further case, and proposes a new classification. (10.1177/1753193413478349)
• [L4] This anomaly is not usually associated with clinical symptoms and should not be routinely excised when encountered. (10.1177/0363546503261712)
• [L5] Several anatomical anomalies were identified, which may explain the difficulty in localizing injury sites and highlight the importance of individualized treatment. (10.1007/s001670050086)
• [L4] The presence of the muscle does not appear to cause any clinical symptoms. (10.1177/1753193409106179)
• [L5] The anterolateral ligament is consistently present. (10.1007/s00167-011-1580-3)
• [L3] The classification system is a repeatable and reliable tool, and consideration of individual shape is required to prevent iatrogenic damage and ensure proper footprint restoration. (10.1007/s00167-015-3891-2)
• [L4] In kneeling, there was a difference in the rotational kinematics between the flexion phase and the extension phase. (10.1186/s13018-022-03080-x)
• [L4] Although MR imaging is the imaging technique of choice, it still has limitations as demonstrated in this case. (10.1007/s00167-006-0037-6)
• [L5] However, neither restored the contact mechanics and kinematics of the ACL-intact knee. (10.1177/0363546513483269)
• [L4] This classification system allows for the ability to evaluate differing repair patterns and their effects on postoperative clinical outcomes. (10.1177/2325967125s00101)
• [L1] The overall failure rate was similar between the anatomical and non-anatomical approaches. (10.1136/jisakos-2020-000476)
• [L5] Standardized testing protocols and techniques are proposed to characterize the biomechanical behavior of the knee and cruciate ligaments to allow comparisons between investigations. (10.1007/s001670050226)
• [L4] The results of the current study may be helpful to improve the understanding of the knee kinematics and develop the physiological knee prostheses. (10.1007/s00167-011-1679-6)
• [L5] The planning of surgical procedures may be improved by the proposed classification. (10.1007/s00167-018-5318-3)
• [L5] The study delineated a consistent three-layered anatomical pattern of the medial knee, suggesting the use of specific nomenclature for the superficial medial ligament and posteromedial capsule rather than the term 'posterior oblique ligament'. (10.2106/00004623-197961010-00011)
• [L4] Knee alignment is different in different individuals and is dynamic in nature, changing with different postures. (10.1302/0301-620x.97b4.33740)
• [L3] In order to improve knowledge on the physiological kinematics of the knee joint and to improve the concept of kinematic knee replacement, the proximal femur seems to be a factor of clinical importance. (10.1007/s00167-014-3343-4)
• [L5] Under physiologic loading conditions, posterior cruciate ligament reconstruction does not restore six degree of freedom knee kinematics. (10.1177/03635465030310040901)
• [L3] Existing arthroplasty techniques are based on assumptions that may not adequately address the anatomy of morphologic outliers and could lead to dissatisfaction. (10.1007/s00167-021-06725-2)
• [L5] No statistically significant differences were found between the two constructs regarding restoration of knee kinematics, mean failure loads, or stiffness. (10.1177/23259671251385225)
• [L3] There were substantial improvements in patient-reported outcomes, showing acceptable midterm clinical healing rates and low reoperation/failure rates. (10.1016/j.arthro.2020.12.150)
• [Case_report] Debridement of the mucoid tissue is a safe and effective treatment method. (10.1007/s00167-009-0885-y)
• [L4] The classification of developmental patterns illustrates the varying directional changes that can occur in lower-extremity length discrepancies and their dependence on underlying biological phenomena. (10.2106/00004623-198264050-00001)
• [L4] The review examines indications, surgical techniques, and outcomes for correcting coronal, sagittal, and axial plane deformities around the knee. (10.1016/j.jisako.2024.04.002)
• [L4] Most commonly utilized radiographic measures were consistent between sexes, across the adolescent age group, and between adolescents and young adults. (10.1016/j.jse.2011.10.026)
• [L4] The heterogeneity of the treatment and outcomes highlights the importance of developing an algorithmic approach to diagnosis and treatment. (10.1177/2325967119s00068)
• [L5] A thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes if cortical blowout occurs despite careful planning and adherence to proper surgical technique. (10.1177/2325967116652122)
• [L5] Given the importance of this structure, it must be reconstructed as anatomically as possible in its insertion and in its shape. (10.1007/s00167-014-3207-y)
• [Case_report] The authors agree that management should begin with nonoperative treatment, but surgery is indicated when diagnosis is in doubt. (10.1177/03635465000280042501)
• [L4] Non-operative treatments are usually ineffective, and while rotational osteotomies are effective, they are associated with significant complication rates. (10.2106/00004623-198567050-00027)
• [L1] The range of knee anatomy in patients scheduled for TKA is wide. (10.1016/j.arth.2017.02.028)
• [L3] Anatomical, MRI-based parameters should be considered before indicating medial reefing. (10.1007/s00167-021-06581-0)
• [L5] They can precisely and reproducibly be defined on radiographs. (10.1016/j.arthro.2007.12.012)
• [L4] Posterolateral rim morphology can be delineated on lateral plain film images, with radiographic type 1 rims correlating with distinct anatomic morphology and radiographic type 2 rims correlating with indistinct morphology. (10.1016/j.arthro.2008.04.072)
• [L5] The integrity of the Kaplan fibers should be routinely reviewed on MRI scans. (10.1177/0363546520919986)
• [L5] The debate between traditional and innovative alignment techniques is set to continue for some time, and individualisation of knee arthroplasty based on patient anatomy, physiology, and kinematics is the future direction. (10.1302/0301-620x.99b2.38085)
• [L5] The authors argue that successful knee surgery depends on a deep anatomical and functional understanding to restore the patient's individual anatomy, rather than on the surgical technique itself, and caution against assuming newer techniques are superior to older ones without sufficient time to evaluate outcomes. (10.1007/s00167-015-3635-3)
• [L5] Owing to its complexity, CFD is best treated by clinicians with considerable deformity treatment experience to maximize functional outcomes. (10.5435/jaaos-d-21-01186)
• [L4] Failure to treat all injured structures can lead to change in knee kinematics and poorer outcome. (10.1177/2325967120s00519)
• [L3] Selective magnetic resonance imaging does not provide enhanced diagnostic utility over clinical examination, particularly in children, and should be used judiciously in cases where the clinical diagnosis is uncertain and magnetic resonance imaging input will alter the treatment plan. (10.1177/03635465010290030601)
• [L4] CT-based phenotyping established a 3D classification of arthritic knee anatomy into 4 foundational morphologies, of which types 1 and 3 represent outliers present in 26% of knees undergoing TKA. (10.2106/jbjs.24.01466)
• [L5] Isometric grafts restore normal knee kinematics regardless of the flexion angle at which they are secured. (10.1007/s001670050221)
• [L3] Focusing on bone morphology allows surgeons to easily perform visual assessment using preoperative radiographs. (10.1186/s12891-022-05526-z)
• [L5] Conventional non-anatomic ACL reconstruction techniques do not prevent early osteoarthritis nor restore normal dynamic knee function; restoring anatomy may be the key to success, but high-quality prospective randomized trials with precise outcome measures are needed to validate benefits. (10.1007/s00167-010-1222-1)
• [L5] The proposed method can evaluate knee joint mechanical parameters such as stress distribution at the joint contact interface. (10.1007/s00167-010-1190-5)
• [L4] Our series demonstrated satisfactory clinical and functional outcomes. (10.1016/j.arthro.2008.04.048)
• [L3] Outcomes were equal or superior to other cartilage repair techniques. (10.1177/2325967120s00501)
• [L5] Biomechanical studies determine the magnitude and direction of forces and moments of various tissues in and around a diarthrodial joint, as well as measure corresponding joint kinematics, to assist clinicians in assessing function and planning treatment. (10.1177/03635465990270042301)
• [L5] However, a better understanding of treatment factors has improved functional results, with current approaches favoring surgical intervention, specialized techniques, and early rehabilitation. (10.1186/s40634-020-00260-8)
• [L5] The algorithm can be used for the 3D reconstruction of other types of 2D cuts, but special attention must be paid with the branches, since the proposed algorithm is not designed for complex branching structures. (10.1186/s13018-022-02994-w)
• [L4] Both techniques provide satisfactory outcomes in most patients with no identifiable differences, suggesting surgeon preference may dictate technique selection. (10.1016/j.arthro.2015.12.017)
• [L5] The knee joint simulator successfully demonstrated the anatomy, physiology, and kinematics of knee ligaments, allowed teaching of ligamentous instability tests, and demonstrated the effect of knee ligament reconstructive surgery. (10.1007/s001670050121)
• [L4] MRI is of crucial significance for operative planning and distinguishing benign from malignant soft-tissue tumors. (10.1007/s001670050073)
• [L5] Comprehensive qualitative and quantitative guidelines for assessing posterolateral knee structures on both anteroposterior and lateral knee radiographs were described. (10.1177/0363546508328117)
• [Letter] MRI can identify ALL injury with good agreement in routine 1.5T MRI, but is not accurate in differentiating complete and partial ALL tears; a consensus on standardization of MRI sequence characteristics and definitions is warranted. (10.1016/j.arthro.2019.05.041)
• [L4] The functional knee phenotype concept better represents the variability of the coronal knee alignment than the conventional system of valgus, varus and neutral. (10.1177/2325967120s00301)
• [L5] Comparative anatomical studies suggest that understanding these shared kinematic principles can improve the design of external bracing systems and total knee replacements. (10.2106/00004623-198769070-00004)
• [L5] Further studies are required to understand if this kind of reconstruction can ameliorate proprioception as well as clinical outcome at a long-term follow-up. (10.1186/1749-799x-2-10)
• [L4] MRIs predict ACL length more reliably than radiographs. (10.1016/j.asmr.2019.10.005)
• [L5] These data facilitate repairs and reconstructions that can restore physiological laxity and stability patterns across the arc of knee flexion. (10.1007/s00167-020-06139-6)
• [Case_report] The absence of injury, the mild complaints reported by the patient, his age, skeletal immaturity, and remaining growth led us to adopt a conservative approach to treating this anatomic variant. (10.1186/s12891-021-04696-6)
• [L3] The challenge will be to identify the optimal alignment strategy for each functional knee phenotype. (10.1177/2325967120s00300)
• [L4] Double-bundle reconstructions may better restore normal knee kinematics than single-bundle reconstructions, although clinical outcomes have not revealed such a difference. (10.1177/0363546511416316)
• [L4] A variety of reliable skeletal maturity estimation systems using routine knee radiographs and MRI are described; orthopaedic surgeons can use these to inform preoperative workups without requiring additional hand radiographs. (10.5435/jaaos-d-24-00133)
• [L4] Surgical release was effective in a case where nonoperative treatment failed. (10.1007/s00167-003-0382-7)
• [L4] Non-operative management is associated with highly variable periods of convalescence, poor return to preinjury level of function and high risk of injury recurrence. (10.1302/2058-5241.5.200055)
• [L4] The presence of chondrosis at the time of surgery is an important prognosticator of functional outcome at intermediate follow-up. (10.1177/0363546507311091)
• [L5] Surgical management is indicated for progressive, painful, unilateral deformity or leg-length discrepancy, while moderate nonprogressive deformity often does not require surgery. (10.5435/00124635-199803000-00003)
• [L4] In patients in whom conservative management fails to ameliorate symptoms, IOBP should be considered. (10.3390/jcm9051358)
• [L5] Most studies have failed to show improved clinical outcomes in the short term when adding cartilage restoration procedures to high tibial osteotomy, raising questions about whether longer term studies will show improved efficacy. (10.1016/j.arthro.2023.07.002)
• [Case_report] If the patient's symptoms are unresponsive to nonoperative treatment, surgical correction can be effective. (10.1177/03635465010290012101)
• [L4] Nonoperative treatment appears to be associated with excellent outcomes based on return to the preinjury level of sport in all athletes in this series. (10.1177/2325967118822450)
• [L5] Many nonoperative modalities exist, yet ultimately operative intervention may be necessary to improve pain and prevent progression to knee osteoarthritis. (10.1002/ksa.70290)
• [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. (10.1002/arj.70105)
• [L4] This study found that cam morphology existed in historical populations at rates comparable with a contemporary population. (10.1097/corr.0000000000001771)
• [L4] Exaggerated physiological deformities may correct spontaneously and should not be stapled before the skeletal age of eleven in girls and twelve in boys. (10.2106/00004623-197961030-00001)
• [L4] The natural course of CECS seems to be persistent symptoms over time. (10.1007/s00167-014-2847-2)
• [Case_report] The report documents the progression of a purely lytic lesion in Paget's disease of the tibia over twelve years, noting that faster longitudinal growth occurred during the first six years before slowing as the disease extended to involve the entire bone. (10.2106/00004623-197658060-00023)
• [L4] The prognosis after excision is excellent, with no recurrences observed in this series. (10.2106/00004623-196749010-00010)
• [L4] Although favorable initial evolution at 30 months after a complete ACL lesion, our series show a re-rupture rate or 'scar tissue' rupture of 40% at a mean follow-up of 8 years. (10.1177/2325967118s00188)
• [L3] The clinical outcomes of OWHTO were affected by cartilage status, rather than by the chronologic age itself. (10.1016/j.arthro.2021.03.075)

See Also

• Anterior Cruciate Ligament

References

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