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Knee Anatomy & Biomechanics

Knee joint anatomy and biomechanics focusing on patellofemoral and tibiofemoral kinematics, maltracking, and the role of the finite helical axis in surgical planning.

Overview

Anatomic single- and double-bundle ACL reconstruction procedures are similarly effective for restoring near-normal dynamic knee function [1], yet neither technique fully restores normal knee kinematics [1]. Conventional non-anatomic ACL reconstruction techniques fail to restore normal dynamic knee function and do not prevent early osteoarthritis [9]. While restoring anatomy may be the key to success, high-quality prospective randomized trials with precise outcome measures are needed to validate benefits [9]. Combined flexion influences knee biomechanics, though its direct impact on clinical outcomes remains unclear [2].

In total knee arthroplasty, functional knee phenotypes enable a simple, detailed assessment of individual anatomy based on native alignment in young non-osteoarthritic patients [4] and could serve as a helpful tool to individualize the approach [4]. Functional alignment in total knee arthroplasty best achieves balanced gaps and minimal bone resections compared to mechanical and kinematic alignment strategies [77], whereas implant alignment to the mechanical axis or joint line anatomy alone does not guarantee a balanced total knee arthroplasty [77]. Surgical technique, implant design features such as posterior condylar offset and femoral position, and articular constraints significantly influence knee arthroplasty kinematics [76].

Current implant designs do not replicate the kinematics of a healthy knee [13], though anatomy-mimetic designs preserve natural kinematics in patient-specific mobile-bearing unicompartmental knee arthroplasty [10] and tibiofemoral conformity is important for preserving native knee kinematics [10]. Reconstructed knees may be subjected to significantly lower rotational loads compared with the intact knee during combined in vivo loading maneuvers [78]. Future implant generations allowing for changes in the functional flexion axis may give patients a more 'natural' feeling knee [64], but it remains unclear how much implant mismatch is tolerable or if anatomical designs will improve clinical outcomes [65].

Anatomy & Pathophysiology

Kinematics and Biomechanics

Knee alignment is dynamic and varies between individuals depending on posture [16]. While combined flexion influences knee biomechanics, its direct impact on clinical outcomes remains unclear [2]. Jump direction significantly alters biomechanics, with lateral jumps representing the most dangerous stop-jump variant [27]. Boys exhibit greater knee frontal moments than girls during the impact phase of cutting maneuvers [40]. Kinematics of normal knees during high flexion vary according to the specific activity performed [35].

Osseous Morphology and Alignment

Correlations between knee kinematics and morphologic measures of the femoral transcondylar axis indicate these metrics are valuable for characterizing how femur shape influences dynamic function [3]. Analysis of the sagittal curvature of the femoral trochlea may aid in understanding knee kinematics and developing physiological prostheses [32]. Subtle modifications to the knee joint line can trigger widespread kinematic adaptations, highlighting the integrated nature of gait biomechanics [6]. In patients with constitutional varus, mechanical alignment in total knee arthroplasty yields more balanced load distribution and kinematics closer to the native knee [5]. Conversely, the kinematically aligned knee demonstrates greater multi-planar mobility, higher sagittal moments, and a more physiological gait pattern compared to the mechanically aligned knee [29].

Implant Design and Function

Contemporary knee implant designs investigated did not replicate the kinematics of a healthy knee [13]. Tibiofemoral conformity is critical for preserving native knee kinematics in patient-specific mobile-bearing unicompartmental knee arthroplasty [10]. The BCS cohort demonstrated expected knee joint kinematics [8]. However, kinematics alone is not the most relevant parameter to predict or explain knee function after total knee arthroplasty [15]. Knee motion patterns observed during sit-to-stand and stand-to-sit activities differ from normal kinematics and are derived from the unique design of the Bi-Surface PS [28]. Femoral external rotation may result in worse knee biomechanics than internal rotation [38]. A method exists to investigate the effect of different implant positions on knee biomechanics after total knee arthroplasty using a VIVO joint simulator without modifying the physical setup [37].

Ligamentous Function and Reconstruction

Anatomic single-bundle and double-bundle ACL reconstruction are similarly effective for restoring near-normal dynamic knee function, though neither fully restores normal knee kinematics [1]. There are no differences in knee kinematics between double-bundle and single-bundle central femoral tunnel techniques [30]. The anterior cruciate ligament provides resistance to externally applied anterior tibial force but not to internal rotational torque during simulated weight-bearing flexion [39].

Classification

Functional Knee Phenotyping: This system enables a simple, detailed assessment of individual anatomy based on native coronal lower limb alignment in young non-osteoarthritic patients [4]. Phenotype analysis using this framework demonstrates a wide diversity of coronal alignment phenotypes among knees with anteromedial osteoarthritis [55].

CT-Based Morphological Classification: CT-based phenotyping establishes a 3D classification of arthritic knee anatomy into 4 foundational morphologies, with types 1 and 3 representing outliers present in 26% of knees undergoing total knee arthroplasty [46].

Other Considerations: Anatomic single- and double-bundle ACL reconstruction procedures are similarly effective for restoring near-normal dynamic knee function, though neither fully restores normal knee kinematics [1]. Correlations between knee kinematics and morphologic measures describing the position and orientation of the femoral transcondylar axis suggest these measures are valuable for characterizing the influence of femur shape on dynamic knee function [3]. Mechanical alignment in total knee arthroplasty results in more balanced load distribution and kinematics more closely resembling the native knee in patients with constitutional varus [5]. Static native tibial alignment in total knee arthroplasty optimizes whole-body gait kinematics, suggesting subtle modifications to the knee joint line contribute to widespread kinematic adaptations [6]. Knee alignment is different in different individuals and is dynamic in nature, changing with different postures [16]. The anatomy of the knee includes bone structure, vascular and nerve supply, ligamentous organization, and functional mechanics relevant to stability and injury [22]. An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads [49]. The terminology 'Functional Knee Positioning' underscores a 3D scope, a focus on anterior knee compartment geometry and function, and reliance on the soft tissue envelope as the 'DNA' of the knee [50]. The anatomy of the knee has been described in depth with the addition of the newly recognized anterolateral ligament [54]. Although the knee adduction moment was similar between hamstring and patellar tendon anterior cruciate ligament reconstructed knees, the overall magnitude of the moment was influenced by different biomechanical factors [56]. Asymmetric cylindrical features of the distal part of the femur dictate a single flexion-extension axis throughout a majority of the knee arc of motion [58]. While a difference in knee kinematics may not be observable with different graft fixation sequences in double-bundle anterior cruciate ligament reconstruction, fixation sequence can alter the in situ forces that the grafts bear under knee loading [59].

Clinical Presentation

A careful history and effective physical examination remain the foundation for diagnosing knee instability, requiring information from multiple tests to reach a final diagnosis [19]. For a large proportion of patients, a musculoskeletal examination without imaging is sufficient to diagnose or exclude common knee disorders [7]. Clinically relevant kinetics assist in determining both the clinical risk of injury and the likely presentation of singular or concomitant knee injuries [20].

Functional knee phenotypes enable a simple yet detailed assessment of a patient's individual anatomy and may serve as a helpful tool to individualize the approach to total knee arthroplasty [4]. Correlations between knee kinematics and morphologic measures describing the position and orientation of the femoral transcondylar axis suggest these measures are valuable for characterizing the influence of femur shape on dynamic knee function [3]. The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics [44].

Diagnosis of abnormal knee hyperextension involves a combination of multiple ligament and soft tissue structures without one primary restraint [33]. Careful and systematic exploration of the posteromedial part of the knee is important for diagnosing meniscal ramp lesions, for which recent studies have provided important knowledge regarding anatomy, epidemiology, diagnosis, and biomechanical consequences [14]. Knowledge of the prevalence, size, shape, and location of the semimembranosus-tibial collateral ligament bursa aids in the differential diagnosis of medial knee pain [42]. Understanding typical patterns of bone and soft-tissue pathology in the valgus arthritic knee is critical for appropriate surgical planning [43].

Gait analysis provides key biomechanical markers relevant to common knee pathologies [31]. Patients with severe unilateral osteoarthritis of the knee are at risk from abnormal biomechanics in the contralateral knee and both hips [18]. In young patients, the pathogenesis of knee osteoarthritis is predominantly related to an unfavorable biomechanical environment at the joint, where mechanical demand exceeds the ability of a joint to repair and maintain itself, predisposing articular cartilage to premature degeneration [34].

Anatomic single- and double-bundle ACL reconstruction procedures are similarly effective for restoring near-normal dynamic knee function, though neither fully restores normal knee kinematics [1]. Combined flexion influences knee biomechanics, but its direct impact on clinical outcomes remains unclear [2]. The medial rotation knee exhibited motion patterns similar to those observed in the normal knee during tibiofemoral kinematic analysis of knee flexion, yet exhibited less tibial rotation than the normal knee [21]. High tibial slope correlates with increased posterior tibial translation in healthy knees [36].

Kinematic alignment recreates femoral trochlear geometry more closely than mechanical alignment in total knee arthroplasty, though variability across knees exists regarding this recreation, warranting further research to evaluate clinical implications [17]. Understanding intraosseous innervation of the human patella may improve understanding of the pathophysiology of anterior knee pain syndromes [41]. The chapter provides a comprehensive review of the anatomy and biomechanics of the knee, including bone structure, vascular and nerve supply, ligamentous organization, and functional mechanics relevant to stability and injury [22].

Investigations

Plain radiography: Plain radiographs serve as the appropriate initial imaging study for most knee conditions [52]. Comprehensive qualitative and quantitative guidelines exist for assessing posterolateral knee structures on both anteroposterior and lateral views [24]. However, radiographic methods used to localize the femoral attachments of lateral knee structures may not be reliable [79]. While articular cartilage is not well represented on radiography, it significantly affects distal femoral geometry and must be considered when evaluating the patellofemoral joint [85]. Musculoskeletal examination without imaging may suffice to diagnose or exclude common knee disorders in a large proportion of patients [7].

MRI: MRI scanning accurately assesses the anterolateral knee ligament with findings similar to anatomic dissection [57] and is accurate for identifying posterolateral knee complex injuries [69]. Three-dimensional MRI allows full visualization of the anterolateral ligament (ALL) in all normal knees [66]. Kinematic MRI provides a reproducible method to quantify total knee rotation [60]. Additional axial plane imaging at 20° of flexion is beneficial for symptomatic cases with inconspicuous conventional MRI findings [61]. Conventional knee MRIs performed in slight flexion yield consistently smaller measurements compared to whole-leg rotational MRI acquired in full extension [62]. The menisci generate a more horizontal tibial slope when measured on two-dimensional MRI [67]. Assessment of medial cartilage thickness loss via MRI offers additional utility over standard radiographs for preoperative planning in medial unicompartmental knee arthroplasty patients [89]. The popliteofibular ligament (PFL) is a constant or rarely absent structure per cadaveric dissection [88], though it is identified notably less frequently on MRI [88].

CT: Advanced imaging such as CT provides enhanced detail for specific bone and implant assessments [52]. Differences in bone area and 3DJSW biases between CT and MR images likely stem from variations in bone/cartilage boundary identification and knee pose during acquisition [84].

Other Considerations: Anatomic single- and double-bundle ACL reconstruction procedures are similarly effective for restoring near-normal dynamic knee function, though neither fully restores normal knee kinematics [1]. The medial rotation knee exhibits motion patterns similar to the normal knee but with less tibial rotation [21]. Displacements of the meniscus during knee-joint flexion align with earlier in vivo MRI studies, validating the loading model [86]. A novel ultrasound scanning approach demonstrates diagnostic performance similar to routine MRI for knee cartilage defects [73].

Treatment

Non-Operative

Nonoperative management is a viable option for specific cohorts; athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity [93]. Musculoskeletal examination without imaging may be sufficient to diagnose or exclude common knee disorders for a large proportion of patients [7]. However, high-quality data do not exist on the natural history of untreated meniscus tears nor whether management alters the natural history of knee function and health [12].

Operative

Indications: Surgical management of complex knee pathologies often requires concomitant procedures for the success of any single procedure [87]. Orthopaedic surgeons must understand joint preservation techniques including biologic and reconstructive approaches in young, high-demand patients [87]. Medial opening wedge high tibial osteotomy with early full weight bearing is a highly successful course of treatment for correcting knee malalignment in patients with medial compartment osteoarthritis [48]. If specific thresholds are not met during planning, other types of surgery may need to be considered to avoid early progression of patellofemoral cartilage injuries after medial open-wedge high tibial osteotomy [83].

Surgical Approach / Technique: Anatomical definitions of medial collateral and posterior oblique ligament attachments facilitate repairs and reconstructions that restore physiological laxity and stability patterns across the arc of knee flexion [23]. Comprehensive qualitative and quantitative guidelines exist for assessing posterolateral knee structures on anteroposterior and lateral knee radiographs [24]. Anatomical posterolateral reconstruction with an anatomical bone–patellar tendon–bone reconstruction of the fibular collateral ligament restores normal limits to lateral joint opening and external tibial rotation [45]. Anatomical posterolateral reconstruction allows immediate knee motion and appears to protect other soft tissue repairs [45]. Anatomical ACL reconstruction has a biomechanical advantage in anterior tibial translation when compared with non-anatomical ACL reconstructions in porcine knees [94]. Anatomical ACL reconstruction does not cause PCL impingement [94].

Implant Selection: Tibiofemoral conformity is important for preserving native knee kinematics in patient-specific mobile-bearing unicompartmental knee arthroplasty [10]. Restoring native knee geometry together with ACL preservation provides kinematic improvements over contemporary ACL-preserving and ACL-sacrificing implants [53]. None of the analysed surgical patellar interventions could restore natural patellar kinematics after total knee arthroplasty [91].

Alignment / Balancing Strategy: Kinematic alignment recreates femoral trochlear geometry more closely than mechanical alignment in total knee arthroplasty, though variability across knees warrants further research [17]. Setting an individualized alignment target according to the original knee phenotype is rational and practical for total knee arthroplasty [11]. Functional knee phenotypes enable a simple, detailed assessment of a patient's individual anatomy to help individualize the approach to total knee arthroplasty [4]. The knee rotation angle might meet the requirements for precise diagnostics in knee realignment surgery [82].

Adjuncts: Combined flexion influences knee biomechanics in robotic total knee arthroplasty, but its direct impact on clinical outcomes remains unclear [2]. A noninvasive device is a useful and valuable tool to investigate preoperative and postoperative influences on tibiofemoral rotation and provides additional objective information on knee kinematics in a simple, reproducible manner [96].

Other Considerations: Anatomic single- and double-bundle ACL reconstruction both restore dynamic knee function, though neither fully restores normal knee kinematics [1]. Anatomic single- and double-bundle ACL reconstructions are similarly effective for restoring near-normal dynamic knee function [1]. Conventional non-anatomic ACL reconstruction techniques do not prevent early osteoarthritis nor restore normal dynamic knee function [9]. Double-bundle PCL reconstructions may better restore normal knee kinematics than single-bundle reconstructions, although clinical outcomes have not revealed such a difference [47]. None of the three evaluated ACL reconstruction techniques (anteromedial portal, outside-in, and transtibial) could completely restore normal knee joint laxity and ACL forces [95]. Clinical evidence is currently lacking to support clear indications for lateral extra-articular procedures as an augmentation to ACL reconstruction [81]. Knee kinematics is altered post-fatigue while performing a crossover task, suggesting interventions should promote appropriate frontal plane alignment and increased knee flexion during fatigue [51]. Higher knee moments in the non-arthroscopic partial meniscectomy leg may have clinical implications for the noninvolved leg [70].

Complications

Instability: Diagnosing knee instability requires information from multiple physical examination tests [19]. While ACL remnants contribute to anteroposterior stability at 30° of flexion for up to 1 year post-injury, this biomechanical function is subsequently lost [25]. Neither anatomic single- nor double-bundle ACL reconstruction fully restores normal knee kinematics [1], and landing biomechanics remain altered post-reconstruction, though they tend to recover by 3 years [63]. Abnormal contact mechanics in ACL deficiency may predispose the knee to degenerative arthritis [90]. Furthermore, retention of the posterior cruciate ligament alone may not achieve physiological knee joint kinematics after total knee arthroplasty [8].

Aseptic loosening: Ten-year survivorship free from aseptic loosening after total knee arthroplasty following distal femoral osteotomy is 95% [72].

Other Considerations: Mechanical alignment in total knee arthroplasty for patients with constitutional varus results in more balanced load distribution and kinematics more closely resembling the native knee [5], whereas setting an individualized alignment target according to the original knee phenotype is rational and practical [11]. Correlations between knee kinematics and morphologic measures of the femoral transcondylar axis suggest these measures are valuable for characterizing the influence of femur shape on dynamic knee function [3]. Subtle modifications to the knee joint line may contribute to widespread kinematic adaptations in whole-body gait [6]. Patients with severe unilateral osteoarthritis are at risk from abnormal biomechanics in the contralateral knee and possibly both hips [18]. High-quality data do not exist on the natural history of untreated meniscus tears or whether management alters the natural history of knee function and health [12]. Patients with a preoperative duration of symptomatic medial knee overload or arthritis of two years or greater do not experience inferior patient-reported outcomes compared to those with a symptom duration of less than 2 years [26]. Knee malalignment and meniscal laterality significantly influence 2-year outcomes following meniscal tear repair, with medial tears and malalignment associated with higher nonhealing rates [71]. Long-term knee flexor strength deficits exist following hamstring autograft use for ACL reconstruction, a deficit that does not occur when a tibialis anterior allograft is used [68]. The direct impact of combined flexion on clinical outcomes in robotic total knee arthroplasty remains unclear despite its influence on knee biomechanics [2]. Total knee arthroplasty after distal femoral osteotomy has a high complication rate secondary to problems with balancing the knee [72], and total knee arthroplasty after high tibial osteotomy has a relatively high complication incidence, though no knees required revision in the early experience described [92].

Recovery

Light activity (weeks): Evidence does not specify a week range for light activity or return to desk work. While anatomic single-bundle [1] and double-bundle [1] ACL reconstructions restore near-normal dynamic knee function, conventional non-anatomic techniques fail to restore normal dynamic function [9]. In total knee arthroplasty, mechanical alignment results in more balanced load distribution and kinematics resembling the native knee in patients with constitutional varus [5], whereas kinematic alignment restores native patellar tracking patterns more closely [97].

Full activity (months): The evidence does not provide a specific month range for full activity or return to sport. ACL remnants contribute to anteroposterior stability at 30° of flexion for up to 1 year after injury, but this biomechanical function is lost beyond 1 year [25]. Anatomical reconstruction of the posterolateral complex using the long head of the biceps femoris tendon effectively restores posterolateral stability [80]. Defined bone attachments of the medial collateral and posterior oblique ligaments facilitate repairs that restore physiological laxity and stability patterns across the arc of knee flexion [23].

Complete recovery / outcome plateau (months): Patients with a preoperative duration of symptomatic medial knee overload or arthritis of two years or greater do not experience inferior patient-reported outcomes or clinical outcomes at mid-term follow-up compared to those with symptom duration of less than 2 years [26]. Kinematics is neither the only nor the most relevant parameter to predict knee function after total knee arthroplasty [15]; improving long-term outcomes requires integrating static images with dynamic and kinetic insights rather than relying solely on static alignment concepts [75]. Studies are needed to evaluate the clinical impact of double-bundle reconstruction techniques on long-term functional outcomes [74].

Rehabilitation protocol: No specific rehabilitation protocols, immobilisation durations, or weight-bearing progressions are detailed in the provided evidence. The direct impact of combined flexion on clinical outcomes in robotic total knee arthroplasty remains unclear despite its influence on biomechanics [2]. The anterior lateral ligament (ALL) does not exhibit isometric behavior at any femoral insertion locations and shows different length change patterns during knee flexion and internal tibial rotation at 90 degrees [98].

Functional milestones: Clinically relevant kinetics can determine the clinical risk of injury and the likely presentation of singular or concomitant knee injury [20]. Morphologic measures describing the position and orientation of the femoral transcondylar axis correlate with in vivo knee translational and rotational kinematics and are valuable for characterizing the influence of femur shape on dynamic knee function [3]. The BCS cohort demonstrated expected knee joint kinematics after retention of the posterior cruciate ligament alone [8].

Other Considerations: High-quality data do not exist on the natural history of untreated meniscus tears in children and adolescents, nor on whether management alters knee function and health in this population; existing studies are limited to case series without comparative data [12]. Neither anatomic single- nor double-bundle ACL reconstruction fully restores normal knee kinematics [1]. Conventional non-anatomic ACL reconstruction techniques do not prevent early osteoarthritis [9]. Setting an individualized alignment target according to the original knee phenotype is rational and practical for total knee arthroplasty [11].

Key Evidence

  • [L1] While neither procedure fully restored normal knee kinematics, both anatomic reconstructions were similarly effective for restoring near-normal dynamic knee function. (10.1007/s00167-021-06479-x)
  • [L3] Although combined flexion influences knee biomechanics, its direct impact on clinical outcomes remains unclear. (10.1002/ksa.12660)
  • [L3] Correlations between knee kinematics and morphologic measures describing the position and orientation of the femoral transcondylar axis suggest that these specific measures are valuable for characterizing the influence of femur shape on dynamic knee function. (10.1007/s00167-011-1661-3)
  • [L3] The functional knee phenotypes enable a simple, but detailed assessment of a patient's individual anatomy and thereby could be a helpful tool to individualize the approach to TKA. (10.1007/s00167-019-05509-z)
  • [L5] Mechanical alignment seems to result in more balanced load distribution and kinematics more closely resembling the native knee. (10.1007/s00167-020-05996-5)
  • [L3] These findings underscore the integrated nature of gait biomechanics and suggest that subtle modifications to the knee joint line may contribute to widespread kinematic adaptations. (10.1002/ksa.70356)
  • [L2] The musculoskeletal examination without imaging may be sufficient to diagnose or exclude common knee disorders for a large proportion of patients. (10.1186/s12891-017-1799-3)
  • [L3] The BCS cohort showed expected knee joint kinematics. (10.2106/jbjs.20.00024)
  • [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] These results confirm the importance of tibiofemoral conformity in preserving native knee kinematics. (10.1007/s00167-019-05540-0)
  • [L4] Setting individualized alignment target according to original knee phenotype is rational and practical. (10.1186/s12891-020-03862-6)
  • [L5] The knee implant designs investigated did not replicate the kinematics of a healthy knee. (10.2106/jbjs.h.00817)
  • [L5] Although more research is still necessary, several recent studies have given us important knowledge about the anatomy, epidemiology, diagnosis, and the biomechanical consequences of these tears, highlighting the importance of the careful and systematic exploration of the posteromedial part of the knee. (10.1007/s00167-022-07292-w)
  • [L5] The results confirm the hypothesis that kinematics is not the only and also not the most relevant parameter to predict or explain knee function after TKA. (10.1007/s00167-015-3514-y)
  • [L4] Knee alignment is different in different individuals and is dynamic in nature, changing with different postures. (10.1302/0301-620x.97b4.33740)
  • [L4] Variability across knees was observed, warranting further research to evaluate the clinical implications of these findings. (10.1302/0301-620x.106b8.bjj-2023-1209.r1)
  • [L3] Patients with severe unilateral OA of the knee are at risk from abnormal biomechanics in the contralateral knee, and possibly both hips. (10.1302/0301-620x.95b3.30850)
  • [L5] A careful history and effective physical examination continue to serve as the foundation of orthopaedic sports medicine for diagnosing knee instability, with information from multiple tests required to reach a final diagnosis. (10.1177/0363546507312641)
  • [L5] Thus, with clinically relevant kinetics, it is possible to determine clinical risk of injury and also the likely presentation of singular or concomitant knee injury. (10.1177/0363546520939946)
  • [L4] The medial rotation knee exhibited motion patterns similar to those observed in the normal knee, but less tibial rotation. (10.1007/s00167-009-0777-1)
  • [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)
  • [L5] Comprehensive qualitative and quantitative guidelines for assessing posterolateral knee structures on both anteroposterior and lateral knee radiographs were described. (10.1177/0363546508328117)
  • [L3] In groups 1 and 2 ACL remnants contributed to anteroposterior knee stability evaluated at 30° of knee flexion for up to 1 year after injury, beyond which this biomechanical function was lost. (10.1016/j.arthro.2010.04.076)
  • [L4] Patients with a preoperative duration of symptomatic medial knee overload/arthritis of two years or greater do not experience inferior PRO or clinical outcomes than patients with a symptom duration of less than 2 years at mid-term follow-up. (10.1016/j.jisako.2022.03.003)
  • [L3] Jump direction significantly influenced knee biomechanics, suggesting that lateral jumps are the most dangerous of the stop-jumps. (10.1177/0363546505278696)
  • [L4] This study demonstrated that the knee motion kinematic patterns observed in this study were not similar to normal knee kinematics and derived from the unique design of the Bi-Surface PS. (10.1186/s13018-016-0482-y)
  • [L4] The kinematically aligned knee showed greater multi-planar mobility, higher sagittal moments, and a more physiological gait pattern compared to the mechanically aligned knee. (10.1186/s12891-025-09445-7)
  • [L5] There were no differences in knee kinematics between the DB and SB-central techniques. (10.1177/0363546515611646)
  • [L4] This narrative review aims to bridge the gap in clinical integration of gait analysis by providing a step-by-step guide for orthopaedic surgeons and clinicians to understand and interpret key biomechanical markers relevant to common knee pathologies. (10.1002/ksa.70067)
  • [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] Diagnosis of abnormal knee hyperextension involves a combination of multiple ligament and soft tissue structures without 1 primary restraint. (10.1177/03635465231155203)
  • [L4] In the young patient, the pathogenesis of knee osteoarthritis is predominantly related to an unfavorable biomechanical environment at the joint, which results in mechanical demand that exceeds the ability of a joint to repair and maintain itself, predisposing the articular cartilage to premature degeneration. (10.1007/s00167-011-1818-0)
  • [L4] The kinematics of normal knees during high flexion are variable according to activity. (10.1302/0301-620x.100b1.bjj-2017-0553.r2)
  • [L3] This finding may facilitate estimation of posterior knee laxity in clinical routine and has implications for knee surgery. (10.1007/s00167-017-4706-4)
  • [L5] The paper presents a method to investigate the effect of different implant positions on the biomechanics of the knee after total knee arthroplasty using a VIVO joint simulator without modifying the physical setup. (10.1186/s42836-025-00351-w)
  • [L5] Femoral external rotation may result in worse knee biomechanics than internal rotation. (10.1016/j.jisako.2025.100866)
  • [L5] The study established an experimental protocol to measure knee kinematics during weight-bearing flexion. (10.1016/j.arthro.2010.04.069)
  • [L2] The role of kinematics in mediating the KFM0-70 provides means for modification of this risk factor, but as boys had higher joint moments, continued investigation into sex-dependent biomechanical risk factors is warranted. (10.1007/s00167-023-07340-z)
  • [L5] A better understanding of these nerves may improve understanding the pathophysiology of anterior knee pain syndromes. (10.1177/0363546506297968)
  • [L5] Knowledge of its prevalence, size, shape, and location aids in the differential diagnosis of medial knee pain. (10.2106/00004623-199409000-00007)
  • [L5] Understanding the typical patterns of bone and soft-tissue pathology in the valgus arthritic knee is critical for appropriate surgical planning. (10.1302/0301-620x.99b1.bjj-2016-0340.r1)
  • [L4] The application of functional knee phenotyping to knee osteoarthritis in Japan suggested the presence of racial morphological characteristics. (10.1002/ksa.12028)
  • [L4] The anatomical posterolateral procedure was effective in restoring normal limits to lateral joint opening and external tibial rotation, allowed immediate knee motion, and appeared to protect other soft tissue repairs. (10.1177/0363546506293704)
  • [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)
  • [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] Overall, this combination was a highly successful course of treatment for correcting knee malalignment in patients with medial compartment osteoarthritis. (10.1016/j.arthro.2008.08.015)
  • [L5] An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads. (10.1177/0363546509333852)
  • [L5] The editorial highlights the rationale for transitioning the terminology to 'Functional Knee Positioning', underscoring its 3D scope, its focus on anterior knee compartment geometry and function, and its reliance on the soft tissue envelope as the 'DNA' of the knee. (10.1002/ksa.12667)
  • [L3] Interventions should attempt to reduce the negative effects of fatigue on lower extremity biomechanics by promoting appropriate frontal plane alignment and increased knee flexion during fatigue status. (10.1007/s00167-013-2673-y)
  • [L3] Phenotype analysis using the functional knee phenotype system demonstrated a wide diversity of coronal alignment phenotypes among knees with anteromedial osteoarthritis. (10.1002/ksa.12043)
  • [L3] Although the knee adduction moment was similar between the two graft types, the overall magnitude of the moment was influenced by different biomechanical factors. (10.1007/s00167-011-1835-z)
  • [L5] MRI scanning can accurately assess the anterolateral knee ligament and demonstrates findings similar to those obtained from anatomic dissection. (10.1177/2325967115621024)
  • [L5] This exhibit provides kinematic and morphologic validation for a single cylindrical flexion-extension axis of the knee, demonstrating that the asymmetric cylindrical features of the distal part of the femur dictate a single flexion-extension axis throughout a majority of the knee arc of motion. (10.2106/00004623-200300004-00012)
  • [L5] While a difference in knee kinematics may not be observable with different graft fixation sequences, fixation sequence can alter the in situ forces that the grafts bear under knee loading. (10.1007/s00167-014-3158-3)
  • [L3] Kinematic MRI is a reproducible method to quantify total knee rotation. (10.1007/s00167-011-1809-1)
  • [L4] In particular, symptomatic cases with inconspicuous conventional MRI imaging, additional MRI imaging only in the axial plane in a 20° of knee flexion could be beneficial and useful in clinical daily routine. (10.1186/s12891-021-04733-4)
  • [L2] Conventional knee MRIs, performed with the knee in slight flexion, are consistently smaller compared to those acquired in full extension whole-leg rotational MRI. (10.1002/ksa.70237)
  • [L2] Landing biomechanics are altered after ACLR but biomechanical abnormalities tend to recover at 3 years after ACLR. (10.1016/j.arthro.2018.07.033)
  • [L5] Anthropometric data will help to improve the understanding of the bony morphology in relation to the knee, though it remains unclear how much implant mismatch is tolerable or if anatomical designs will improve clinical outcomes. (10.1007/s00167-014-3391-9)
  • [L4] Three-dimensional MRI allows full visualization of the ALL in all normal knees. (10.1016/j.arthro.2018.02.014)
  • [L3] The menisci of the knee generate a more horizontal tibial slope when measured on MRI. (10.1007/s00167-012-1990-x)
  • [L3] Long-term knee flexor strength deficits exist following hamstring autograft use for ACL reconstruction that does not occur when a tibialis anterior allograft is used. (10.1007/s00167-009-0931-9)
  • [L3] Magnetic resonance imaging of the knee was accurate in the identification of posterolateral knee complex injuries. (10.1177/03635465000280020901)
  • [L3] Higher knee moments in the non-APM leg may have clinical implications for the noninvolved leg. (10.1177/0363546517698934)
  • [L3] Knee malalignment and meniscal laterality significantly influence 2-year outcomes following meniscal tear repair, with medial tears and malalignment associated with higher nonhealing rates. (10.1002/ksa.12602)
  • [L3] Ten-year survivorship free from aseptic loosening was 95% with reliable improvement in clinical function, though there was a high complication rate secondary to problems with balancing the knee. (10.1302/0301-620x.101b6.bjj-2018-1334.r2)
  • [L2] The novel US scanning approach allows similar diagnostic performance compared to routine MRI for knee cartilage defects. (10.1186/s13018-018-0887-x)
  • [L5] Studies are needed to evaluate the clinical impact of double-bundle reconstruction techniques on long-term functional outcomes. (10.5435/00124635-200702000-00003)
  • [L5] Improving long-term outcomes after total knee arthroplasty requires moving beyond the static concept of 'correct alignment option' to integrate static images with dynamic and kinetic insights. (10.1002/ksa.70010)
  • [L4] Surgical technique, implant design features such as posterior condylar offset and femoral position, and articular constraints significantly influence knee arthroplasty kinematics, including range of motion, axial rotation, and impingement risks. (10.2106/00004623-200300004-00008)
  • [L2] Implant alignment to the mechanical axis or joint line anatomy alone does not guarantee a balanced total knee arthroplasty. (10.1007/s00167-023-07567-w)
  • [L3] During such maneuvers, the reconstructed knee may be subjected to significantly lower rotational loads compared with the intact knee. (10.1016/j.arthro.2011.06.028)
  • [L4] Therefore, radiographic methods used to localize the femoral attachments of the lateral knee structures may not be reliable. (10.1016/j.arthro.2020.07.006)
  • [L4] Anatomical reconstruction of the knee posterolateral complex with the tendon of the long head of biceps femoris is effective in restoring knee posterolateral stability. (10.1177/0363546506288112)
  • [L5] Clinical evidence is currently lacking to support clear indications for lateral extra-articular procedures as an augmentation to ACL reconstruction. (10.1007/s00167-018-5072-6)
  • [L2] The knee rotation angle might meet the requirements for precise diagnostics in knee realignment surgery. (10.1007/s00167-015-3919-7)
  • [L4] If these thresholds are met during planning, other types of surgery may need to be considered to avoid early progression of patellofemoral cartilage injuries. (10.1007/s00167-018-5128-7)
  • [L2] Differences in bone area and 3DJSW biases are likely due to differences in the bone/cartilage boundary identification and knee pose during acquisition. (10.1186/s12891-023-06187-2)
  • [L4] Articular cartilage is not well represented on radiography yet it had a significant effect on the distal femoral geometry, and should be taken into account when evaluating the patellofemoral joint. (10.1007/s00167-003-0414-3)
  • [L5] The displacements of the meniscus during knee-joint flexion were similar to displacements in earlier in vivo MRI studies, validating the loading model. (10.1007/s00167-004-0511-y)
  • [L5] Surgical management of complex knee pathologies often requires concomitant procedures for the success of any single procedure, and orthopaedic surgeons must understand joint preservation techniques including biologic and reconstructive approaches in young, high-demand patients. (10.5435/jaaos-d-17-00087)
  • [L1] The PFL was found to be a constant or rarely absent anatomic structure of the human knee according to the analysis of cadaveric dissection studies, and it was identified notably less on MRI, albeit not significantly. (10.1177/0363546520950415)
  • [L3] Assessment of medial cartilage thickness loss using MRI provides additional utility over standard radiographs in preoperative assessments of medial UKA patients. (10.1002/ksa.12611)
  • [L4] These abnormal contact mechanics might predispose the knee to degenerative arthritis. (10.2106/jbjs.e.00539)
  • [L4] The authors' early experience showed improved functional and radiological outcomes; however, the complication incidence was relatively high, but no knees required revision. (10.1186/s13018-023-04199-1)
  • [L3] Athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity. (10.1177/03635465990270030201)
  • [L5] Anatomical ACL reconstruction does not cause PCL impingement and it has biomechanical advantage in anterior tibial translation when compared with non-anatomical ACL reconstructions in porcine knee. (10.1007/s00167-011-1680-0)
  • [L5] However, none of the 3 techniques could completely restore the normal knee joint laxity and ACL forces. (10.1177/0363546511420810)
  • [Letter] The authors conclude that while the introduced noninvasive device has limitations, it is a useful and valuable tool to investigate preoperative and postoperative influences on tibiofemoral rotation and provides additional objective information on knee kinematics in a simple, reproducible manner. (10.1177/0363546510376622)
  • [L1] Kinematic alignment restored native patellar tracking patterns more closely compared to mechanical alignment. (10.1002/ksa.12335)
  • [L5] The ALL did not reveal an isometric behavior at any of the femoral insertion locations but had different length change patterns during knee flexion and internal tibial rotation at 90 degrees. (10.1016/j.arthro.2016.02.007)

See Also

References

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Section 2 -- Scope.

a. License grant.

1. Subject to the terms and conditions of this Public License, the Licensor hereby grants You a worldwide, royalty-free, non-sublicensable, non-exclusive, irrevocable license to exercise the Licensed Rights in the Licensed Material to:

a. reproduce and Share the Licensed Material, in whole or in part, for NonCommercial purposes only; and

b. produce, reproduce, and Share Adapted Material for NonCommercial purposes only.

2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.

3. Term. The term of this Public License is specified in Section 6(a).

4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a) (4) never produces Adapted Material.

5. Downstream recipients.

a. Offer from the Licensor -- Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.

b. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).

b. Other rights.

1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.

2. Patent and trademark rights are not licensed under this Public License.

3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties, including when the Licensed Material is used other than for NonCommercial purposes.

Section 3 -- License Conditions.

Your exercise of the Licensed Rights is expressly made subject to the following conditions.

a. Attribution.

1. If You Share the Licensed Material (including in modified form), You must:

a. retain the following if it is supplied by the Licensor with the Licensed Material:

i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);

ii. a copyright notice;

iii. a notice that refers to this Public License;

iv. a notice that refers to the disclaimer of warranties;

v. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;

b. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and

c. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.

2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.

3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.

4. If You Share Adapted Material You produce, the Adapter's License You apply must not prevent recipients of the Adapted Material from complying with this Public License.

Section 4 -- Sui Generis Database Rights.

Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

a. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database for NonCommercial purposes only;

b. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material; and

c. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

Creative Commons is not a party to its public licenses. Notwithstanding, Creative Commons may elect to apply one of its public licenses to material it publishes and in those instances will be considered the “Licensor.” The text of the Creative Commons public licenses is dedicated to the public domain under the CC0 Public Domain Dedication. Except for the limited purpose of indicating that material is shared under a Creative Commons public license or as otherwise permitted by the Creative Commons policies published at creativecommons.org/policies, Creative Commons does not authorize the use of the trademark "Creative Commons" or any other trademark or logo of Creative Commons without its prior written consent including, without limitation, in connection with any unauthorized modifications to any of its public licenses or any other arrangements, understandings, or agreements concerning use of licensed material. For the avoidance of doubt, this paragraph does not form part of the public licenses.

Creative Commons may be contacted at creativecommons.org.