Meniscus & Collateral Ligaments

Meniscal and collateral ligament injuries: management of traumatic vs degenerative tears and the role of repair in preventing joint degeneration.

Overview

For selected patients with persistent chronic tibial collateral ligament strain due to occult medial meniscus derangement, the treatment of choice is anteromedial arthrotomy and medial meniscectomy [4]. Knee partial meniscectomy has limited benefit for nonobstructive meniscal tears [102]. It is necessary to determine if patients with nonobstructive meniscal tears have osteoarthritis to establish indications for surgical versus nonsurgical treatment [102].

According to current standard indications, 34.9% of all meniscal injuries offer the potential for repair [11]. Meniscal repair potential rises to 55.6% when injuries are accompanied by anterior cruciate ligament damage [11]. Meniscal repair is a viable alternative to resection in many clinical situations, with success rates exceeding 80% when performed with anterior cruciate ligament reconstruction [21]. Although the failure rate of meniscus repair may be greater in an unstable knee, meniscal repair is not contraindicated in a knee with a deficient ACL [22]. Medial meniscus repair in the ACL-deficient knee is not contraindicated [13].

The menisci should be repaired if at all possible, especially in the setting of anterior cruciate ligament reconstruction, for optimal functional outcome and patient satisfaction [85]. Meniscal repair in ACL reconstructed knees with expanded indications achieved a healing rate (including incomplete healing) of 75% [87]. In appropriately selected patients, meniscal repair can deliver improved subjective outcomes with comparable reoperation rates versus meniscectomy [92]. Meniscal repair has the potential for reduced risk of osteoarthritis over time versus meniscectomy in appropriately selected patients [92].

Surgical intervention for medial meniscal root tears aims to improve outcomes associated with nonoperative management, but it is unclear which patients are suitable candidates [18]. There is not yet clear consensus on indications for surgical intervention for medial meniscal root tears [18]. It is unclear whether meniscectomy is an acceptable treatment for medial meniscal root tears [18]. Meniscal allograft shows adequate outcomes for proper indications as a salvage procedure [20]. The International Meniscus Reconstruction Experts Forum (IMREF) 2015 Consensus Statement outlines a standardized approach to indications, surgical technique, and postoperative care for meniscal allograft transplantation [100]. The goal of the IMREF 2015 Consensus Statement is optimizing patient outcomes for meniscal allograft transplantation [100].

Anatomy & Pathophysiology

Meniscal Biomechanics and Attachments

The anterior intermeniscal ligament plays a critical role in load distribution; its sectioning increases femorotibial contact pressures, decreases contact areas, and shifts the force center of application more centrally within the joint [30]. Decreased displacement of the medial meniscus correlates with higher pressure on knee components, suggesting a biomechanical risk for knee degeneration [35]. Forces at the anterior meniscus attachments increase significantly under dynamic knee joint loading [43]. In vitro models applying uniaxial loads with static flexion angles or very low flexion-extension speeds underestimate these attachment forces [43].

Meniscal integrity directly influences ligamentous stress and kinematics. Different medial meniscal resections increase knee laxity and peak tensile stress in the anterior cruciate ligament (ACL), potentially leading to collagen fiber fatigue tearing and altered mechanobiology under normal joint loads [48]. ACL deficiency reduces physiological extrusion of the medial meniscus during axial load-bearing and causes altered biomechanics characterized by increased anterior-posterior motion and rotational instability [40]. Surgical interventions such as arthroscopic centralization for lateral meniscal injuries reduce laxity in ACL-reconstructed knees but may overconstrain the knee in certain motions [47].

Restoration of meniscal function improves joint mechanics. Autologous semitendinosus meniscus grafts significantly improve knee joint kinematics after complete lateral meniscectomy, with doubled grafts restoring tibiofemoral contact mechanics to levels almost comparable to the native situation [41]. Meniscal healing is a multifactorial process requiring both biologic and kinematic factors, making the restoration of proper knee biomechanics pivotal [34]. However, optimal rehabilitation protocols for meniscal healing remain contradictory, and further studies are needed to understand growth factor kinetics and achieve higher healing rates [34].

Collateral Ligament Anatomy and Biomechanics

The bone attachments of the medial collateral ligament (MCL) and posterior oblique ligament (POL) are defined anatomically and radiographically [33]. Defining these attachments facilitates repairs and reconstructions that restore physiological laxity and stability patterns across the arc of knee flexion [33]. The superficial MCL, deep MCL, and POL exhibit specific length-change patterns across knee flexion and under various loads, providing biomechanical data to inform surgical repair or reconstruction strategies [37].

MCL integrity is crucial for outcomes in arthroplasty. Understanding MCL anatomy and biomechanics is essential for good outcomes after total knee arthroplasty [36]. Intraoperative injury to the MCL during total knee arthroplasty is an uncommon yet serious complication that often goes unrecognized [36]. In unicompartmental knee arthroplasty (UKA), overstuffing leads to more valgus alignment, higher MCL strains, and altered contact forces, whereas understuffing results in biomechanics closest to the native knee [31].

Multiligament and Complex Instability

Multiligamentous knee injuries involve complex biomechanical disruption where total joint instability exceeds the sum of individual ligamentous injuries [38]. Recognition of secondary stabilizers is necessary in these injuries to prevent failure [38]. Comprehensive treatment of all contributing factors is required to prevent failure in multiligamentous knee injuries [38].

Patellofemoral and General Kinematics

Radiographic measures of patellar tracking and alignment change with knee motion [46]. In knees with patellofemoral instability symptoms, these radiographic measures are most abnormal at lower flexion angles [46]. Patellofemoral instability is a complex pathology with a considerable number of different influencing factors [49]. A detailed understanding of anatomy and kinematics is required to identify underlying pathologies in patellofemoral instability [49].

Diagnostic and Interventional Devices

A noninvasive device serves as a useful and valuable tool to investigate preoperative and postoperative influences on tibiofemoral rotation [42]. This device provides additional objective information on knee kinematics in a simple, reproducible manner, though it has limitations [42]. Patients with knee osteoarthritis and degenerative medial meniscal tear who used a biomechanical foot-worn device for a year showed improvement in gait, physical function, and pain [45].

Evolutionary and Comparative Perspectives

Comparative anatomical studies of the knee suggest that understanding shared kinematic principles can improve the design of external bracing systems and total knee replacements [32]. A chronological examination of meniscal biomechanics studies over the past 40 years identifies concepts, theories, methods, and developments achieved in the field [39]. This examination also identifies likely directions for future research [39].

Classification

The medial collateral ligament complex is the most commonly injured knee ligament [5]. The medial side of the knee has a consistent three-layered anatomical pattern [95]. Specific nomenclature for the superficial medial ligament and posteromedial capsule is suggested rather than the term 'posterior oblique ligament' [95]. A distinct plane exists between the posterior knee capsule and the meniscotibial ligament complex [74]. The distance between the physis and meniscotibial ligament capsular attachments increases with age [74]. No subtypes were detected in the medial meniscus in a cadaver study evaluating morphological variations [77].

Discoid Lateral Meniscus: Clinical grading of instability clarifies the natural history of discoid lateral meniscus-associated tearing [10]. An arthroscopic classification system for discoid lateral menisci is based on morphology and instability [51].

Medial Meniscal Ramp Tear: A medial meniscal ramp tear classification system for patients undergoing anterior cruciate ligament reconstruction (ACLR) is based on anatomic and arthroscopic morphologic tear documentation [54]. Recent research has provided terminology, classification systems, and anatomical and biomechanical knowledge to understand the importance of properly diagnosing and treating meniscal ramp lesions [68]. There is limited consistency in descriptive classifications used for meniscal ramp lesions [94]. It is crucial to differentiate between subtypes of lateral meniscus tears, specifically identifying 'ramp-like' lateral meniscus tears in patients with concomitant anterior cruciate ligament ruptures and associated instability [70].

Multiple Ligament Knee Injury (MLKI): The current multiple ligament knee injury (MLKI) classification system is more than 20 years old [73]. A proposed MLKI classification system includes each specific structure injured, modifiers for fractures, extensor mechanism injuries, nerve injuries, or vascular injuries, specific anatomic location of structures injured (meniscus and articular cartilage), and injury timing (acute, chronic) [73].

Meniscal Extrusion: Global perspectives on meniscal extrusion classification support the development of a new classification measured on MRI scans at the mid-tibial plateau that considers laterality, anatomical location, age, BMI, and aetiology [98].

Other Considerations: Several histological scoring systems are available to assess meniscal structure, but few have been validated for specific application in research settings [67]. A scoring system to predict the reparability of meniscus, limited to tears identifiable by MRI after testing the classification of zones and patterns of meniscal tear based on MRI, has limitations regarding MRI sensitivity, statistical details, and demographic data [69]. Surgical decision making is based on patient factors and understanding of the meniscal structure, function, and pathology [103].

Clinical Presentation

Chronic Degeneration and Long-Term Outcomes: Patients with intact menisci and normal articular cartilage demonstrate significantly better outcomes than those who have undergone meniscectomy or possess damaged cartilage [1]. However, the long-term prognosis remains guarded; at 10 to 20 years post-diagnosis, approximately 50% of patients with a diagnosed anterior cruciate ligament or meniscus tear develop osteoarthritis accompanied by pain and functional impairment [3]. In medial knee osteoarthritis, the specific type of medial meniscal tear correlates with characteristic clinical symptoms reported by patients [55].

Medial Compartment Pathology: The medial collateral ligament is the most commonly injured knee ligament [5]. Persistent chronic tibial collateral ligament strain may indicate an occult medial meniscus derangement [4]. Anterior medial meniscus detachment combined with an anterior cruciate ligament tear is a relatively rare injury that is difficult to diagnose via MRI [19].

Lateral Meniscus Anomalies: Symptomatic discoid lateral meniscus occurs most frequently in teenagers [16], though cases of discoid meniscus are generally uncommon [56] and their etiology remains unknown [56]. The radiographic condylar cut-off sign offers moderate diagnostic utility for complete discoid lateral meniscus in adolescents aged 10–16 [15]. Patient presentations and treatments for discoid medial menisci are similar to those for discoid lateral menisci [59]. Differentiation between a ring meniscus and an incomplete discoid meniscus requires careful probing during arthroscopy [14]. Double-layered lateral meniscus is an extremely rare anatomical abnormality [58].

Acute Instability and Complex Injuries: MRI is a sensitive measure for cruciate and collateral ligament injury in acute knee dislocation but does not reliably diagnose injury to the posterolateral corner or meniscus in this setting [12]. Consequently, a higher index of suspicion is required during arthroscopy to prevent misdiagnosis of posterolateral corner or meniscus injury in acute knee dislocation, as missed lesions can negatively affect long-term clinical outcomes [12]. Management of complex knee instability necessitates a comprehensive workup including assessment of alignment, menisci, cartilage, and concurrent ligament injuries, as isolated injuries are rare and missed concomitant lesions can lead to reconstruction failure [17]. A posterior lateral meniscus root tear is a clinically relevant but likely underrecognized concomitant injury in patients with an ACL tear [52].

Meniscal Extrusion and Management: In patients with three or more millimetres of meniscus extrusion, an intact meniscus, and minimal knee pathology, a meniscotibial ligament abnormality is likely [53]. Management of meniscal tears is predicated on symptoms, as many symptomatic tears become asymptomatic over time [57].

Investigations

Plain radiography: Plain radiographs are useful for assessing alignment and detecting concurrent ligament injuries as part of a comprehensive workup for complex knee instability [17]. In children, several plain radiographic findings in symptomatic discoid lateral meniscus differ significantly from normal controls [80]. Prediction models improve the diagnostic utility of plain radiography for detecting complete discoid lateral meniscus in children [91]. The lateral femoral notch sign helps establish an ACL tear diagnosis in more than one-quarter of patients [101]. For preoperative sizing in meniscus allograft transplantation, neither MRI nor radiography is highly accurate [93].

MRI: MRI is a sensitive measure of cruciate and collateral ligament injury in acute knee dislocation [12]. However, MRI does not reliably diagnose injury to the posterolateral corner or meniscus in acute knee dislocation [12]. The diagnostic validity of MRI is similar for meniscal tears in acute knee trauma and in knee symptoms lasting over 6 months in young adults [88]. MRI is slightly more accurate than radiography in preoperative sizing for meniscus allograft transplantation, though neither modality is highly accurate [93]. Direct MRI measurement of the contralateral intact meniscus better predicts actual meniscal size than indirect estimation from tibial plateau measurement [109]. There were no differences between right and left meniscal measurements according to MRI in the studied subset of patients [90]. Intravenous or intraarticular contrast-enhanced magnetic resonance arthrography has increased accuracy in detecting recurrent meniscal tears [104]. Meniscal parameters alteration could be an important imaging biomarker to predict the occurrence of radiographic knee osteoarthritis [105]. Among patients with MRI-verified meniscal lesions, 58% could be treated conservatively with good results [106]. Magnetic resonance imaging is only moderately reliable for the prediction of meniscus reparability [108]. The accuracy of MRI in diagnosing discoid lateral meniscus is significantly lower in the presence of radial or longitudinal tears [110]. Anterior medial meniscus detachment and anterior cruciate ligament tear is relatively rare and difficult to diagnose via MRI [19].

Other Considerations: The condylar cut-off sign has a moderate degree of diagnostic utility for complete discoid lateral meniscus in adolescents aged 10–16 [15]. The meniscus should be probed carefully to differentiate between ring meniscus and incomplete discoid meniscus [14]. Meniscocapsular separation can involve a segment of less than 5 mm in length [27]. Meniscocapsular separation can be occult on MRI [27]. Meniscocapsular separation can be challenging to visualize on arthroscopy [27]. Meniscocapsular separation can lead to chronic medial-side knee pain [27]. Arthroscopic repair may result in slower progression of radiological deterioration compared with meniscectomy and nonoperative management for acute meniscus root tears [26].

Treatment

Non-Operative

High-quality data on the natural history of untreated meniscus tears are lacking, with existing studies limited to case series and no comparative trials [9]. Non-operative treatment is the first-line choice for degenerative meniscal lesions, a stance supported by the orthopaedic community [63, 79]. Current evidence indicates that arthroscopic partial meniscectomy (APM) offers limited benefits for adults with degenerative and nonobstructive symptoms, showing outcomes similar to physical therapy [97]. Consequently, APM is reserved for cases where conservative management fails [63, 79]. For traumatic tears, meniscal preservation remains the primary objective [63]. Medial meniscal tears present a complex dilemma where partial meniscectomy must be weighed against long-term degenerative consequences; many are correctly managed non-operatively, with tear location and type influencing the success of such treatment [75, 99].

Operative

Indications: Meniscal repair is indicated for traumatic tears, with current standard indications allowing for repair in 34.9% of all meniscal injuries [11]. This rate rises to 55.6% when the injury is accompanied by anterior cruciate ligament (ACL) damage [11]. Meniscal preservation is the first-line choice for traumatic tears [63]. Strict adherence to indications ensures that meniscal transplantation yields good and predictable results [64]. For medial meniscal root tears, surgical intervention aims to improve outcomes associated with nonoperative management, though consensus on specific indications and the acceptability of meniscectomy remains unclear [18].

Surgical Approach / Technique: Meniscal repair is a viable alternative to resection in many clinical situations, with success rates exceeding 80% when performed concurrently with ACL reconstruction [21]. Repairing a meniscus is considered safe and effective long-term, as subsequent meniscectomy is performed infrequently [6]. Satisfactory clinical outcomes are achievable for radial meniscal tear repair at short-term follow-up [8]. Medial meniscus repair in the ACL-deficient knee is not contraindicated, despite a potentially higher failure rate in unstable knees [13, 22]. Arthroscopic repair may result in slower progression of radiological deterioration compared with meniscectomy and nonoperative management [26]. Complete healing of both menisci was confirmed arthroscopically three years postoperatively in a case involving radial tears in the roots of the posterior horns of both the medial and lateral menisci combined with an ACL tear [50]. The results also demonstrate the long-term efficacy of arthroscopic treatment for symptomatic discoid lateral meniscus [60].

Implant Selection: Meniscal repair systems appear safe and effective, providing a high rate of meniscal healing in patients with complex tears and those with tears located in Cooper radial zone 2 [78]. For meniscal allograft transplantation, medial and lateral meniscus allografts show no significant difference in graft survivorship or patient-reported outcome measures [7]. Positive outcomes are most likely in appropriately selected patients, with studies reporting long-term graft survivorship as high as 89% at 10 years and significant improvements in multiple patient-reported outcome measures [25]. Meniscal allograft transplantation shows adequate outcomes as a salvage procedure for proper indications [20]. The ultimate success of the operation depends on the allograft healing in an anatomic position to support proper meniscal functioning and preserve hyaline cartilage [72].

Other Considerations: Patients with both menisci present and normal articular cartilage have significantly better outcomes than those with meniscectomies or damaged cartilage [1]. Long-term evaluation of ACL-reconstructed knees with concurrent successful meniscal repairs demonstrates a low rate of radiographic arthritis [2]. Clinical outcomes for patients undergoing meniscus repair are better than those undergoing meniscus resection with concurrent ACL reconstruction [76]. Although medial meniscus root repair may heal in a lax manner, it still provides benefit by delaying the radiographic progression of knee osteoarthritis compared to subtotal meniscectomy [71]. Guidelines support the use of meniscal surgery in patients with clearly defined indications while reducing exposure to unnecessary surgery [66]. Evidence supports meniscal repair and conservative treatment, yet meniscectomy remains overused due to non-scientific factors such as technical difficulty, cost, and patient preferences; a critical analysis of the literature is required to reduce unnecessary resections [65].

Complications

Long-term Osteoarthritis and Functional Decline: Patients with meniscectomies or damaged articular cartilage have significantly worse outcomes than those with both menisci present and normal articular cartilage [1]. On average, 50% of patients with a diagnosed anterior cruciate ligament or meniscus tear develop osteoarthritis with associated pain and functional impairment at 10 to 20 years after diagnosis [3]. Long-term evaluation of anterior cruciate ligament–reconstructed knees with concurrent successful meniscal repairs demonstrates a low rate of radiographic arthritis [2].

Surgical Timing and Technique Complications: Partial meniscectomy for irreparable medial meniscal tears applied during the same surgery with anterior cruciate ligament reconstruction negatively affects clinical outcomes in the short-term follow-up [24]. Resection of a single inferior leaflet after a horizontal medial meniscal tear preserves much of the original biomechanical function of the meniscus [107]. Long symptomatic duration (≥6 months) and asymmetrical shape of discoid lateral meniscus are more frequently related to articular cartilage lesions than other factors [28].

Occult Pathology and Chronic Pain: Occult medial meniscus derangement can cause persistent chronic tibial collateral ligament strain [4]. Meniscocapsular separation can be occult on MRI, challenging to visualize on arthroscopy, and lead to chronic medial-side knee pain [27].

Other Considerations: Meniscal allografts are not as durable as the native meniscus [82]. Long-term transplant function and any chondroprotective effects of meniscal transplantation remain unknown and require further investigation [83].

Recovery

Light activity (weeks): Evidence does not provide specific week ranges for light activity or desk work return.

Full activity (months): Evidence does not provide specific month ranges for full activity or sport return.

Complete recovery / outcome plateau (months): Evidence does not provide specific month ranges for outcome plateau.

Rehabilitation protocol: Evidence does not specify immobilisation duration, weight-bearing status, or rehabilitation phasing.

Functional milestones: Patients with both menisci present and normal articular cartilage had significantly better outcomes than those with meniscectomies or damaged cartilage [1]. Long-term evaluation of anterior cruciate ligament–reconstructed knees with concurrent successful meniscal repairs demonstrated a low rate of radiographic arthritis [2]. At 10 to 20 years after diagnosis, on average, 50% of those with a diagnosed anterior cruciate ligament or meniscus tear have osteoarthritis with associated pain and functional impairment [3]. A meniscectomy after meniscal repair is performed infrequently, supporting the notion that repairing a meniscus is a safe and effective procedure in the long term [6]. Medial and lateral meniscus allografts show no significant difference in graft survivorship or patient-reported outcome measures [7]. Satisfactory clinical outcomes are achievable for radial meniscal tear repair at short-term follow-up [8]. Lateral and medial meniscus tears left in situ at the time of ACL reconstruction did not require reoperation at a minimum 6-year follow-up for 97.8% and 94.4% of tears, respectively [23]. Partial meniscectomy for irreparable medial meniscal tears, applied during the same surgery with anterior cruciate ligament reconstruction, negatively affects the clinical outcomes in the short-term follow-up [24]. Long-term results after viable meniscus allograft transplantation are encouraging in terms of pain relief and improvement of function [81]. Meniscus allograft transplantation (MAT) is a viable and effective surgical option for the painful meniscus-deficient knee, with good survivorship and functional outcomes in the medium to long term [89]. 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 [114]. Early repair of an injured medial ligament can be expected to give the patient an excellent chance of returning to his or her prior athletic pursuits [115].

Other Considerations: 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, and all existing studies are at best case series with no comparative studies [9]. Clinical grading of instability has clarified the natural history of discoid lateral meniscus-associated tearing [10]. Long symptomatic duration (≥6 months) and asymmetrical shape of discoid lateral meniscus were more frequently related to articular cartilage lesions than other factors [28]. Longitudinal lateral meniscal tears in ACL-deficient knees do not involve secondary meniscal pathology but derive from a primary recent injury, and the recent lateral meniscal lesion does not evolve in meniscal length and depth [29]. Orthopaedic opinion favors salvaging and restoring the damaged meniscus where possible to provide symptom relief and restore form and function for long-term knee health [84]. In female patients who experienced an ACL injury, a delay in surgery greater than 12 months is associated with a gradual increase in the risk of nonrepairable medial meniscal tear; this risk becomes statistically significant after 24 months [111]. The short-term results of delayed meniscus transplantation were close to those of meniscectomy [112]. At long-term follow-up (>8 years), shrinkage of transplanted fresh-frozen meniscal allografts progressed at 1 year postoperative, was on average mild, and was more prominent in the mid-body than in the anterior or posterior horn [113].

Key Evidence

• [L3] Patients with both menisci present and normal articular cartilage had significantly better outcomes than those with meniscectomies or damaged cartilage. (10.1177/03635465000280040201)
• [L4] The long-term evaluation of the anterior cruciate ligament–reconstructed knees with concurrent successful meniscal repairs demonstrated a low rate of radiographic arthritis. (10.1177/0363546510392014)
• [L4] At 10 to 20 years after diagnosis, on average, 50% of those with a diagnosed anterior cruciate ligament or meniscus tear have osteoarthritis with associated pain and functional impairment. (10.1177/0363546507307396)
• [L4] For selected patients with persistent chronic tibial collateral ligament strain due to occult medial meniscus derangement, the treatment of choice is anteromedial arthrotomy and medial meniscectomy. (10.2106/00004623-195436010-00012)
• [L5] The medial collateral ligament complex has been neglected in terms of study and understanding despite being the most commonly injured knee ligament, and the authors argue it demands more interest and research to obtain objective evidence for surgical decision-making. (10.1007/s00167-020-06116-z)
• [L3] A meniscectomy after meniscal repair is performed infrequently, supporting the notion that repairing a meniscus is a safe and effective procedure in the long term. (10.1177/0363546513503444)
• [Commentary] Medial and lateral meniscus allografts show no significant difference in graft survivorship or patient-reported outcome measures. (10.1016/j.arthro.2020.09.050)
• [L3] Satisfactory clinical outcomes are achievable for radial meniscal tear repair at short-term follow-up. (10.1177/0363546518786035)
• [L3] Clinical grading of instability has clarified the natural history of discoid lateral meniscus-associated tearing. (10.1007/s00167-023-07521-w)
• [L4] According to current standard indications, 34.9% of all meniscal injuries offer the potential for repair, rising to 55.6% when accompanied by anterior cruciate ligament damage. (10.1016/j.arthro.2018.08.051)
• [L2] MRI is a sensitive measure of cruciate and collateral ligament injury in acute knee dislocation; however, it does not reliably diagnose injury to the posterolateral corner or meniscus, and therefore, a higher index of suspicion is required during arthroscopy to prevent misdiagnosis which could affect long-term clinical outcome. (10.1007/s00167-015-3857-4)
• [L4] Medial meniscus repair in the ACL-deficient knee is not contraindicated. (10.1007/s00167-006-0162-2)
• [Case_report] The meniscus should be probed carefully to differentiate between these conditions. (10.1007/s00167-009-0924-8)
• [L2] The condylar cut-off sign has a moderate degree of diagnostic utility for complete discoid lateral meniscus in adolescents aged 10–16. (10.1007/s00167-016-4361-1)
• [L4] Symptomatic discoid lateral meniscus occurred most often in teenagers. (10.1007/s00167-021-06635-3)
• [L5] The authors state that treating complex knee instability requires a comprehensive workup including assessment of alignment, menisci, cartilage, and concurrent ligament injuries, as isolated injuries are rare and missed concomitant lesions can lead to reconstruction failure. (10.1007/s00167-015-3665-x)
• [L5] Although surgical intervention aims to improve the known poor outcomes associated with nonoperative management of medial meniscal root tears, it is unclear which patients are suitable candidates, and there is not yet clear consensus on indications or whether meniscectomy is ever an acceptable treatment. (10.1016/j.arthro.2024.12.020)
• [L4] This type of meniscus injury is relatively rare and difficult to diagnose via MRI; early ACL reconstruction is recommended to avoid progression of meniscal injury and facilitate repair. (10.1007/s00167-006-0255-y)
• [L5] Meniscal allograft, for proper indications, shows adequate outcomes (for a salvage procedure). (10.1016/j.arthro.2015.02.042)
• [L4] Meniscal repair is a viable alternative to resection in many clinical situations, with success rates exceeding 80% when performed with anterior cruciate ligament reconstruction. (10.5435/00124635-200205000-00004)
• [L3] Although the failure rate of meniscus repair may be greater in an unstable knee, meniscal repair is not contraindicated in a knee with a deficient ACL. (10.1007/s00264-004-0616-4)
• [L3] Lateral and medial meniscus tears left in situ at the time of ACL reconstruction did not require reoperation at a minimum 6-year follow-up for 97.8% and 94.4% of tears, respectively. (10.1177/0363546515604622)
• [L4] Partial meniscectomy for irreparable medial meniscal tears, applied during the same surgery with anterior cruciate ligament reconstruction, negatively affects the clinical outcomes in the short-term follow-up. (10.1007/s00167-014-2960-2)
• [L5] Positive outcomes for meniscal allograft transplantation are most likely to be achieved when performed in appropriately selected patients, with studies reporting long-term graft survivorship as high as 89% at 10 years and significant improvements in multiple patient reported outcome measures. (10.1007/s00167-020-06058-6)
• [L4] The current level 3 and 4 evidence suggests that arthroscopic repair may result in slower progression of radiological deterioration compared with meniscectomy and nonoperative management. (10.1177/03635465211031250)
• [L4] Meniscocapsular separation can involve a segment of less than 5 mm in length, be occult on MRI, be challenging to visualize on arthroscopy, and lead to chronic medial-side knee pain. (10.1016/j.arthro.2011.06.025)
• [L4] Long symptomatic duration (≥6 months) and asymmetrical shape of discoid lateral meniscus were more frequently related to articular cartilage lesions than other factors. (10.1016/j.arthro.2009.06.024)
• [L4] Longitudinal lateral meniscal tears in ACL-deficient knees do not involve secondary meniscal pathology but derive from a primary recent injury, and the recent lateral meniscal lesion does not evolve in meniscal length and depth. (10.1007/s001670050068)
• [L5] The section of the intermeniscal ligament leads to substantial changes in knee biomechanics, increasing femorotibial contact pressures, decreasing contact areas, and finally moving the force center of application, which becomes more central inside the joint. (10.1016/j.arthro.2018.03.007)
• [L5] Overstuffing leads to more valgus, higher medial collateral ligament strains, and altered contact forces, while understuffing results in biomechanics closest to the native knee. (10.1007/s00167-015-3848-5)
• [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] 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)
• [Letter] Meniscal healing is a multifactorial process requiring both biologic and kinematic factors; while restoring proper knee biomechanics is pivotal, optimal rehabilitation protocols remain contradictory, and further studies are needed to understand growth factor kinetics and achieve higher healing rates. (10.1016/j.arthro.2022.06.010)
• [Paper] The decreased displacement of the medial meniscus may explain the higher pressure on the knee components, indicating potential biomechanical risk of knee degeneration. (10.1186/s12891-021-04187-8)
• [L5] Understanding the anatomy and biomechanics of the medial collateral ligament is crucial for good outcomes after total knee arthroplasty, and intraoperative injury to the MCL is an uncommon yet serious complication that often goes unrecognized. (10.5435/jaaos-d-19-00355)
• [L5] The study defines the length-change patterns of the superficial MCL, deep MCL, and POL across knee flexion and under various loads, providing biomechanical data to inform surgical repair or reconstruction strategies. (10.1007/s00167-020-06050-0)
• [Paper] Multiligamentous knee injuries involve a complex biomechanical disruption where total joint instability exceeds the sum of individual ligamentous injuries, necessitating recognition of secondary stabilizers and comprehensive treatment of all contributing factors to prevent failure. (10.1016/j.csm.2018.11.009)
• [L5] This study focuses on a chronological examination of studies on meniscus biomechanics in order to introduce concepts, theories, methods, and developments achieved over the past 40 years and also to identify the likely direction for future research. (10.1186/s12891-021-04492-2)
• [L3] These findings indicate altered medial meniscus biomechanics due to increased anterior-posterior meniscal motion and rotational instability after ACL injury. (10.1002/ksa.12269)
• [L5] The doubled ST lateral meniscus autograft improved the knee joint kinematics significantly and restored the tibiofemoral contact mechanics almost comparable to the native situation. (10.1007/s00167-022-07300-z)
• [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)
• [L5] In vitro tests applying uniaxial loads combined with static knee flexion angles or very low flexion-extension speeds appear to underestimate meniscus attachment forces. (10.1177/0363546520988039)
• [L5] The ALL shows no isometric behavior during the range of motion of the knee. (10.1177/2325967114562205)
• [L4] Patients with knee OA and a degenerative medial meniscal tear using a biomechanical foot-worn device for a year showed improvement in gait, physical function and pain. (10.1007/s00167-012-2026-2)
• [L3] Radiographic measures of tracking and alignment changed with knee motion and, in knees with instability symptoms, were most abnormal at lower flexion angles. (10.1016/j.arthro.2014.04.036)
• [L5] However, the procedure may overconstrain the knee in certain motions. (10.1177/03635465211041747)
• [L5] Different medial meniscal resections may increase knee laxity and peak tensile stress in the ACL, potentially leading to collagen fiber fatigue tearing and altered mechanobiology under normal joint loadings. (10.1186/s12891-024-07201-x)
• [L5] Patellofemoral instability represents a complex pathology with a considerable number of different influencing factors, requiring a detailed understanding of anatomy and kinematics to identify underlying pathologies. (10.1007/s00167-018-4860-3)
• [Case_report] Complete healing of both menisci was confirmed arthroscopically 3 years postoperatively, and the restoration of a stable and functional knee joint testifies to the efficacy of the treatment strategy. (10.1007/s00167-009-0839-4)
• [L4] An arthroscopic classification system for discoid lateral menisci is proposed based on morphology and instability. (10.1016/j.arthro.2006.09.002)
• [L5] A posterior lateral meniscus root tear is a clinical relevant but most likely underrecognized concomitant injury in patients with a tear of the ACL. (10.1007/s00167-014-2904-x)
• [L4] In patients with three or more millimetres of meniscus extrusion, an intact meniscus and minimal knee pathology, meniscotibial ligament abnormality is likely. (10.1007/s00167-019-05612-1)
• [L4] This study shows that it was possible to establish a medial meniscal ramp tear classification system for patients undergoing ACLR based on anatomic and arthroscopic morphologic tear documentation. (10.1016/j.arthro.2025.03.015)
• [L3] This study demonstrates a relationship between the type of medial meniscal tear and characteristic clinical symptoms reported by patients with medial knee osteoarthritis. (10.1007/s00167-014-2939-z)
• [Case_report] Cases of discoid meniscus are uncommon, and their etiology remains unknown. (10.1177/2325967124s00401)
• [L4] This case demonstrates an interesting and extremely rare anatomical abnormality of the lateral meniscus. (10.1007/s00167-011-1536-7)
• [L4] Patient presentations and treatments for those with discoid medial menisci were similar to those reported for patients with discoid lateral menisci. (10.1177/03635465231159671)
• [L4] The results showed the long-term efficacy of arthroscopic treatment of a symptomatic discoid lateral meniscus. (10.1007/s00167-011-1440-1)
• [L5] Meniscal preservation is the first-line choice for traumatic tears, while non-operative treatment should be the first-line choice for degenerative meniscal lesions, with arthroscopic partial meniscectomy reserved for failure of conservative management. (10.1302/2058-5241.2.160056)
• [L4] Strictly following the indications, meniscal transplantation can give good and predictable results. (10.1177/0363546510375399)
• [L5] The paper argues that while evidence supports meniscal repair and conservative treatment, meniscectomy remains overused due to non-scientific factors like technical difficulty, cost, and patient preferences; it calls for a critical analysis of literature to reduce unnecessary resections. (10.1007/s00167-014-3471-x)
• [L5] The guidelines support the use of meniscal surgery in patients with clearly defined indications while reducing exposure to unnecessary surgery. (10.1302/0301-620x.101b6.bjj-2019-0550)
• [L3] Although several histological scoring systems are available to assess meniscal structure, only few of them have been validated for specific application in research settings. (10.1007/s00167-012-2142-z)
• [L5] Recent research has provided the necessary terminology, classification systems, and anatomical and biomechanical knowledge to understand the importance of properly diagnosing and eventually treating meniscal ramp lesions. (10.1007/s00167-022-07184-z)
• [L5] The authors appreciate the attempt to formulate a scoring system to predict the reparability of meniscus, limited to tears identifiable by MRI after testing the classification of zones and patterns of meniscal tear based on MRI, but highlight limitations regarding MRI sensitivity, statistical details, and demographic data. (10.1007/s00167-019-05825-4)
• [L4] It is crucial to differentiate between subtypes of lateral meniscus tears, specifically identifying 'ramp-like' lateral meniscus tears in patients with concomitant anterior cruciate ligament ruptures and associated instability. (10.1016/j.jisako.2024.04.005)
• [Commentary] Although medial meniscus root repair may heal in a lax manner, there is still some benefit in delaying radiographic progression of knee osteoarthritis compared to subtotal meniscectomy, and patients should be counseled on the importance of compliance with non-weight-bearing restrictions for the first 6 weeks. (10.1016/j.arthro.2019.07.004)
• [L4] The ultimate success of the operation depends on the allograft healing in an anatomic position to support proper meniscal functioning and preserve hyaline cartilage. (10.1007/s001670050207)
• [Paper] The current MLKI classification system is now more than 20 years old and certainly represents an improvement over previous classification systems; however, it is our hope that by creating a classification system that includes each specific structure injured, modifiers for fractures, extensor mechanism injuries, nerve injuries, or vascular injuries, as well as specific anatomic location of structures injured meniscus and articular cartilage injuries, and injury timing (acute, chronic) that we can use this information to guide further research in this field and to ultimately improve patient care. (10.1016/j.csm.2018.11.006)
• [L5] This defines a distinct plane between the posterior knee capsule and the meniscotibial ligament complex, with a distance between the physis and meniscotibial ligament capsular attachments that increases with age. (10.1016/j.asmr.2023.100852)
• [L5] Meniscal tear location in addition to type likely plays a crucial role in dictating the success of non-operative treatment of the menisci. (10.1007/s00167-018-5090-4)
• [L3] Clinical outcomes of patients that underwent meniscus repair were better than those that underwent meniscus resection with concurrent ACL reconstruction. (10.1007/s00167-020-05931-8)
• [L4] No subtypes were detected in the medial meniscus. (10.1007/s00167-013-2612-y)
• [L3] These meniscal repair systems appeared to be safe and effective, providing a high rate of meniscal healing both in patients with complex tears and in patients with tears located in Cooper radial zone 2. (10.1016/j.arthro.2008.03.003)
• [L5] Meniscal preservation is a major issue and non-surgical treatment is the first-line treatment for degenerative meniscal lesions, though APM remains appropriate in selected cases. (10.1007/s00167-020-06411-9)
• [L2] Several plain radiographic findings in symptomatic discoid lateral meniscus in children were significantly different from those in normal controls. (10.1007/s00167-014-2924-6)
• [L4] Long-term results after viable meniscus allograft transplantation are encouraging in terms of pain relief and improvement of function. (10.1007/s00167-005-0033-2)
• [L4] Meniscal allografts were able to provide subjective improvement at 20 years after surgery and while not as durable as the native meniscus, the overall graft survivorship was 56.2% after implantation. (10.1016/j.arthro.2020.04.029)
• [L3] The short-term results of meniscal transplantation are encouraging in terms of reducing knee pain and increasing function; however, long-term transplant function and any chondroprotective effects remain unknown and require further investigation. (10.2106/jbjs.e.00347)
• [L5] Orthopaedic opinion favors salvaging and restoring the damaged meniscus where possible to provide symptom relief and restore form and function for long-term knee health. (10.1177/0363546513498503)
• [L3] The menisci should be repaired if at all possible, especially in the setting of anterior cruciate ligament reconstruction, for optimal functional outcome and patient satisfaction. (10.1177/03635465020300061501)
• [L3] Both operative and nonoperative management of MCL tears demonstrated clinical improvements between study enrollment and 2-year follow-up. (10.1016/j.arthro.2018.10.138)
• [L4] Meniscal repair in ACL reconstructed knees with expanded indications achieved a healing rate (including incomplete healing) of 75%. (10.1016/j.arthro.2019.04.009)
• [L2] The diagnostic validity of magnetic resonance imaging is similar for meniscal tears in acute knee trauma and in knee symptoms lasting over 6 months in young adults. (10.1177/0363546508329543)
• [L4] MAT is a viable and effective surgical option for the painful meniscus-deficient knee, with good survivorship and functional outcomes in the medium to long term. (10.1016/j.arthro.2018.01.010)
• [L4] There were no differences between right and left meniscal measurements according to MRI in this small subset of patients. (10.1016/j.arthro.2014.05.009)
• [L3] The results of this study provide improved diagnostic utility of plain radiography for the detection of completed discoid lateral meniscus in children. (10.1016/j.arthro.2017.08.252)
• [L5] In appropriately selected patients, meniscal repair can deliver improved subjective outcomes with comparable reoperation rates and the potential for reduced risk of osteoarthritis over time versus meniscectomy. (10.1016/j.arthro.2024.11.058)
• [L4] Magnetic resonance imaging is slightly more accurate than radiography in preoperative sizing for meniscus allograft transplantation, but neither technique is highly accurate. (10.1177/03635465000280041301)
• [L1] Although there has been a recent increase in the recognition and treatment of meniscal ramp lesions, there is limited consistency in descriptive classifications used for this pathology. (10.1002/ksa.12188)
• [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] Completely ruptured collateral ligaments frequently result in prolonged disability when treated non-operatively, whereas surgical repair of fourteen fingers with complete rupture yielded satisfactory results with restored joint stability and pain relief. (10.2106/00004623-196749020-00009)
• [L1] The benefits of APM in adults with degenerative and nonobstructive meniscal symptoms are limited, with current evidence reporting similarity in outcomes between APM and physical therapy. (10.1007/s00167-022-07040-0)
• [L4] The findings shed light on global perspectives regarding meniscal extrusion classification, supporting the development of a new classification measured on MRI scans at the mid-tibial plateau that considers laterality, anatomical location, age, BMI, and aetiology. (10.1002/ksa.12183)
• [L5] Medial meniscal tears pose a more challenging dilemma where partial meniscectomy must be balanced against long-term degenerative consequences, and many tears are correctly treated non-operatively. (10.1007/s00167-021-06694-6)
• [L5] The consensus statement outlines a standardized approach to indications, surgical technique, and postoperative care for meniscal allograft transplantation with the goal of optimizing patient outcomes. (10.1177/0363546516660064)
• [L4] In more than one-quarter of patients, plain radiographs may help to establish the diagnosis of an ACL tear. (10.1007/s00167-014-3022-5)
• [L5] Knee partial meniscectomy has limited benefit for nonobstructive meniscal tears, but it is necessary to determine if included patients have osteoarthritis to establish indications for surgical versus nonsurgical treatment. (10.1016/j.arthro.2016.07.013)
• [L5] Surgical decision making is based on patient factors and understanding of the meniscal structure, function, and pathology. (10.5435/00124635-200205000-00003)
• [L2] We demonstrated an increased accuracy of intravenous or intraarticular contrast-enhanced magnetic resonance arthrography in detecting recurrent meniscal tears. (10.1177/03635465030310062301)
• [L3] The meniscal parameters alteration could be an important imaging biomarker to predict the occurrence of ROA. (10.1186/s12891-024-07706-5)
• [L2] Among a consecutive group of patients with MRI-verified meniscal lesions, 58% could be treated conservatively with good results. (10.1007/s00167-013-2494-z)
• [L5] Resection of a single inferior leaflet after a horizontal medial meniscal tear preserves much of the original biomechanical function of the meniscus. (10.1177/0363546515623782)
• [L3] The results of this study suggest that magnetic resonance imaging is only moderately reliable for the prediction of meniscus reparability. (10.1177/03635465990270040601)
• [L2] Direct MRI measurement of the contralateral intact meniscus better predicts actual meniscal size than estimation of size indirectly from measurement of the tibial plateau on which it is located. (10.1016/j.arthro.2007.06.018)
• [L3] The accuracy of MRI in diagnosing discoid lateral meniscus is significantly lower in the presence of radial or longitudinal tears. (10.1007/s00167-017-4704-6)
• [L3] In female patients who experienced an ACL injury, a delay in surgery greater than 12 months is associated with a gradual increase in the risk of nonrepairable medial meniscal tear; this risk becomes statistically significant after 24 months. (10.1016/j.arthro.2022.10.014)
• [L3] The short-term results of delayed meniscus transplantation were close to those of meniscectomy. (10.1177/0363546514541653)
• [L4] At long-term follow-up (>8 years), shrinkage of transplanted fresh-frozen meniscal allografts progressed at 1 year postoperative, was on average mild, and was more prominent in the mid-body than in the anterior or posterior horn. (10.1016/j.arthro.2019.04.031)
• [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)
• [L4] Early repair of an injured medial ligament can be expected to give the patient an excellent chance of returning to his or her prior athletic pursuits. (10.2106/00004623-197860010-00008)

See Also

• Anterior Cruciate Ligament
• Biomechanics
• Anatomy

References

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