Ligament & Meniscus Pathology

Meniscal and ligamentous pathology: management of traumatic vs degenerative tears, root tear repair, and the role of arthroscopy in preventing joint degeneration.

Overview

Current evidence indicates that meniscal repair is a viable alternative to resection in many clinical situations, with success rates exceeding 80% when performed concomitantly with anterior cruciate ligament reconstruction [16]. While only 34.9% of all meniscal injuries offer the potential for repair under standard indications, this figure rises to 55.6% when the injury is accompanied by anterior cruciate ligament damage [7]. Medial meniscus repair in the ACL-deficient knee is not contraindicated, and 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 [9, 111].

Clinical decision-making requires careful stratification of patient factors. It is necessary to determine if patients have osteoarthritis to establish indications for surgical versus nonsurgical treatment [102], as knee partial meniscectomy has limited benefit for nonobstructive meniscal tears [102]. Patients with ACL reconstruction and meniscal resections do not exhibit decreased clinical outcomes at 2 years postoperatively [6], and meniscal repair in ACL reconstructed knees with expanded indications achieved a healing rate (including incomplete healing) of 75% [85]. A recommendation for ACL reconstruction within 6 months after trauma was made to preserve the meniscus and reduce the risk of developing OA due to a significantly higher rate of prognostically advantageous meniscal repair [106].

Despite these findings, further studies are needed to define the relative importance of individual histologic findings in the clinical setting of meniscus tear and repair [4]. Evaluating the usefulness of meniscectomy is flawed due to insufficient stratification of meniscal tear characteristics [109], and clinical practice guidelines may be flawed if they recommend against treatments that benefit specific patient subgroups despite Level I evidence showing safety and efficacy [109]. While meniscal allograft shows adequate outcomes for proper indications as a salvage procedure [18], current practice guidelines for the ACL-deficient knee with single-compartment osteoarthritis include pathoanatomy, indications, contraindications, technical considerations, and clinical outcomes [19].

Anatomy & Pathophysiology

Kinematics and Biomechanics

Jump direction significantly influences knee biomechanics, with lateral jumps identified as the most dangerous of stop-jumps [26]. The anterior cruciate ligament provides resistance to externally applied anterior tibial force but not to internal rotational torque during simulated weight-bearing flexion [34]. Fixation of a posterior cruciate ligament graft with the knee in flexion and an anterior tibial load best restores intact knee biomechanics [35]. Both fixation protocols for double-bundle anterior cruciate ligament reconstruction restore knee kinematics without predisposing either graft to failure [36]. The position of an anterior cruciate ligament graft is the most critical surgical variable because it has a direct effect on knee biomechanics and, ultimately, on clinical outcome [42].

Ligamentous Reconstruction and Kinematic Restoration

Neither anatomic single-bundle nor double-bundle ACL reconstruction fully restores normal knee kinematics [27]. Both anatomic single-bundle and double-bundle ACL reconstructions are similarly effective for restoring near-normal dynamic knee function [27]. There are no differences in knee kinematics between double-bundle and single-bundle techniques using a central femoral tunnel [28]. The effective role of the anatomical double-bundle procedure in better restoring knee kinematics should be questioned in an in vivo model [37]. Kinematics of the anterior cruciate ligament injured knee did not change significantly after ligament reconstruction, but functional results were satisfactory and knee laxity was diminished [40]. 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 [41]. Knee biomechanics in the leg with ACL reconstruction are altered mainly in the sagittal plane during side-cutting compared with the contralateral leg [31].

Medial Collateral and Anterolateral Complexes

Altering the normal length of the superficial medial collateral ligament results in measurable changes in knee kinematics and stability [30]. Finite element analysis models can effectively analyze the biomechanical functions of the superficial and deep layers of the medial collateral ligaments [33]. An intricate relationship exists among the main medial knee structures and their individual components for static function to applied loads [38]. Knowledge of the biomechanical function of the anterolateral components is lacking, and further research is required to evaluate the influence of the anterolateral capsule on rotatory laxity of the knee [45].

Meniscal Pathophysiology

Surgical treatment of medial meniscus posterior root repair allows restoration of physiological knee joint biomechanics [29]. Sectioning of the anterior intermeniscal ligament leads to substantial changes in knee biomechanics, increasing femorotibial contact pressures and decreasing contact areas [43]. Sectioning of the anterior intermeniscal ligament moves the force center of application more central inside the joint [43].

Clinical Assessment and Bracing

No braces are currently available with biomechanical evidence that satisfies the requirements of applying correct anatomic joint forces that vary with the knee flexion angle [32]. Proper use of physical examination techniques requires understanding of the anatomy and biomechanical principles of the knee as well as the pathophysiology of the injuries [39]. Knee kinematics derived from the one-leg rise test were reliable for asymptomatic and ACL-injured knees [44].

Classification

Arthroscopic Morphology: An arthroscopic classification system for discoid lateral menisci is proposed based on morphology and instability [63]. This system distinguishes subtypes of lateral meniscus tears, specifically identifying 'ramp-like' lateral meniscus tears in patients with concomitant anterior cruciate ligament ruptures and associated instability [78].

Schatzker: Meniscal tears are commonly seen in each Schatzker classification of operative tibial plateau fractures, with longitudinal tears being the most common pattern [75].

Medial Meniscal Ramp: A medial meniscal ramp tear classification system for patients undergoing ACL reconstruction can be established based on anatomic and arthroscopic morphologic tear documentation [76].

Kaplan Fiber: The classification system used to report Kaplan fiber injury was associated with low inter-rater reliability [77]. The presence of Kaplan fiber injury was not associated with other injuries commonly observed in conjunction with ACL tear [77].

Outerbridge: There is a high prevalence of articular cartilage damage as defined by the Outerbridge classification in patients undergoing arthroscopic surgery for meniscal pathology [89].

Other Considerations: A ligamentous structure associated with discoid meniscus is an important differential diagnosis for symptoms usually referred to as meniscus pathology [1]. Further studies are needed to define the relative importance of individual histologic findings in the clinical setting of meniscus tear and repair [4]. Although several histological scoring systems are available to assess meniscal structure, only a few have been validated for specific application in research settings [50]. A higher incidence of ligament and meniscal injuries was noted with higher-grade subtypes of tibial avulsion of the posterior cruciate ligament [56]. No subtypes of morphological variations were detected in the medial meniscus in a cadaver study [62]. Various meniscal tear classifications induce nuanced synovial inflammation [83]. The type and location of meniscal tears differ in young athletes with a stable knee compared to those seen in ACL-deficient knees [91]. The degree of ligament injury patterns and the side of the injured collateral ligament influenced the type and incidence of meniscal damage in multiligament injured knees [101]. Both meniscal repair and resection in anterior cruciate ligament-reconstructed knees were associated with new cartilage lesions [104].

Clinical Presentation

The clinical presentation of ligamentous and meniscal pathology often overlaps, requiring careful differentiation. A ligamentous structure associated with discoid meniscus serves as an important differential diagnosis for symptoms typically attributed to meniscus pathology [1]. In adults, the discoid meniscus lesion represents an atypical clinical entity with no significant predictive value of clinical signs for diagnosis [46]. Presenting symptoms in cases of accessory lateral discoid meniscus may actually stem from a concurrent medial meniscus tear, while the accessory lateral meniscus is found incidentally [47]. The discoid medial meniscus remains a rare abnormality with significant associated morbidity [60].

Diagnostic accuracy varies by modality and injury type. MRI: 1.5-Tesla MRI accurately diagnoses ACL and medial meniscal tears and can reliably complete the diagnostic workup following physical examination, particularly in young adults [10]. However, MR diagnosis of a partial ACL tear is difficult because various tear patterns may be seen, with many partial tears demonstrating MR features indistinguishable from complete ACL tear, mucoid ACL degeneration, or normal ACL [11]. Anterior medial meniscus detachment and anterior cruciate ligament tear is a relatively rare injury type that is difficult to diagnose via MRI [8]. Medial meniscal ramp lesions were present in approximately 17% of patients undergoing ACL reconstruction, yet less than one-half of these lesions were diagnosed on preoperative MRI [13]. Tears of the posterior horn of the medial meniscus may be underdiagnosed by intraoperative assessment using only an anterolateral portal view during ACL reconstruction [59]. The double ACL sign can be a supportive finding for diagnosis and preoperative planning for meniscus injury [53].

Physical examination remains a cornerstone of diagnosis. Clinical examination by an experienced examiner using multiple meniscus tests is sufficient for a diagnosis of a meniscal tear [55]. The meniscal pseudocyst is a new clinical sign characterized by a lump protruding from the joint line, most prominent at 45° of flexion [58]. This sign has a complete correlation with meniscal tears requiring surgical intervention [58]. In patients with three or more millimetres of meniscus extrusion, an intact meniscus, and minimal knee pathology, meniscotibial ligament abnormality is likely [48].

Long-term sequelae and inflammatory profiles provide critical context for chronic presentations. 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 [2]. ACL and meniscal injuries display a pro-inflammatory phenotype in synovial fluid at the time of knee arthroscopy [51]. Conversely, cartilage lesions exhibited a synovial fluid inflammatory profile distinct from ACL and meniscal injury at the time of knee arthroscopy [51]. More severe cartilage lesions were associated with a reduced presence of anti-inflammatory markers in synovial fluid at the time of knee arthroscopy [51]. Anterior cruciate ligament mucoid degeneration needs to be more broadly known and properly diagnosed so that progress can be made in its management [49].

Bone scan utility is time-dependent. Clinically useful positive predictive values for intra-articular abnormalities on bone scans were found only for medial meniscus lesions when time since ACL rupture was more than 18 months [3]. Clinically useful positive predictive values for intra-articular abnormalities on bone scans were found only for local cartilage degeneration when markedly increased uptake was seen when time since ACL rupture was more than 4 months [3].

Surgical outcomes and injury evolution also inform clinical expectations. Eighty-three percent of menisci were symptom-free regardless of meniscal integrity after arthroscopic meniscal repair with the FasT-Fix during ACL reconstruction [14]. Newly formed injuries may occur even in asymptomatic cases following arthroscopic meniscal repair with the FasT-Fix during ACL reconstruction [14].

Investigations

Plain radiography: Can be used to screen for and diagnose discoid lateral meniscus [66]. Several plain radiographic findings in symptomatic discoid lateral meniscus in children were significantly different from those in normal controls [105]. Radiographic measurements of meniscal size are less accurate than MRI measurements, though the difference is very small and likely has limited influence on clinical outcomes [86]. Using radiographs to determine meniscal size for transplantation appears reasonable without compromising clinical outcome [86]. Radiography is slightly more accurate than MRI in preoperative sizing for meniscus allograft transplantation, yet neither modality is highly accurate for this specific purpose [98].

MRI: 1.5-Tesla MRI accurately diagnoses anterior cruciate ligament and medial meniscal tears and can reliably complete the diagnostic workup following physical examination, particularly in young adults [10]. 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 [93]. MRI is the best method for accurately evaluating meniscal cysts as it can demonstrate all visible features of these lesions [79]. MRI contributes to enhancing the diagnostic accuracy of an unhealed meniscal repair when there are limited clinical signs of meniscal pathology [88]. MRI is successful in determining the presence or absence of tears in discoid menisci, though its ability to determine tear type in discoid menisci is questionable [99]. MR diagnosis of partial anterior cruciate ligament tear is difficult because various tear patterns may be seen; many partial tears demonstrate MR features indistinguishable from complete tears, mucoid degeneration, or a normal ligament [11]. MRI is not always useful in predicting reparability of symptomatic isolated lateral semilunar meniscus tears, as most symptomatic cases with normal MRI for these tears were reparable [92]. Anterior medial meniscus detachment and anterior cruciate ligament tear is a relatively rare injury that is difficult to diagnose via MRI [8]. Intra-articular abnormalities did not explain all scintigraphic patterns in anterior cruciate ligament deficiency [3]. MRI did not reveal normal menisci in all cases following polyurethane meniscal scaffold implantation for partial meniscal deficiency [74]. All 24 knees in a long-term follow-up of operated lateral tibial plateau fractures exhibited MRI abnormalities, with an unexpectedly high number of pathological changes in the menisci and ligaments developing in the long term [84]. Development of new cartilage lesions was evident after 2-year follow-up in patients with arthroscopic anterior cruciate ligament reconstruction as detected by MR imaging [108]. Medial meniscal ramp lesions were present in approximately 17% of patients undergoing anterior cruciate ligament reconstruction, yet less than one-half were diagnosed on preoperative MRI [13]. The diagnostic accuracy of MRI for multiple ligament knee injuries largely varied among knee structures, with many structures at risk of misdiagnosis, especially posterolateral corner, meniscal, and chondral lesions [97]. The anterior meniscofemoral ligament of the medial meniscus is a rare anomaly that is often unrecognized and underreported; MRI rarely detects this ligament, and it may be obscured during arthroscopy [107].

Bone scan: Clinically useful positive predictive values for bone scans in anterior cruciate ligament deficiency were found only for medial meniscus lesions when time since rupture was more than 18 months [3]. Clinically useful positive predictive values for bone scans in anterior cruciate ligament deficiency were found only for local cartilage degeneration when markedly increased uptake was seen and time since rupture was more than 4 months [3].

Other Considerations: A ligamentous structure associated with discoid meniscus is an important differential diagnosis for symptoms usually referred to as meniscus pathology [1]. Early anterior cruciate ligament reconstruction is recommended for anterior medial meniscus detachment to avoid progression of meniscal injury and facilitate repair [8].

Treatment

Non-Operative

Non-operative management provides symptomatic relief for most patients with degenerative posterior root tears of the medial meniscus [81]. Initial non-operative treatment is recommended for anterior horn tears noted on MRI among patients without mechanical symptoms and whose clinical examination is inconsistent with a pathologic meniscal condition [103]. Arthroscopic partial meniscectomy should not be proposed as a first-line treatment for degenerative meniscus lesions; non-operative treatment should always be started first, with surgery only envisaged after its failure [87, 110]. Non-surgical treatment for acute medial meniscus posterior root tear did not result in any significant change in clinical outcomes from the initial to the final follow-up [113]. Meniscal tear location in addition to type likely plays a crucial role in dictating the success of non-operative treatment of the menisci [90]. Initial nonoperative management of degenerative meniscal tears is worth a try [115]. However, nonoperative management of pediatric and adolescent ACL injuries resulted in high rates of residual knee instability, increased risk of meniscal tears, and comparatively low rates of return to sports [114].

Operative

Indications: According to current standard indications, 34.9% of all meniscal injuries offer the potential for repair [7]. The potential for meniscal repair rises to 55.6% when the injury is accompanied by anterior cruciate ligament damage [7]. Medial meniscus repair in the ACL-deficient knee is not contraindicated [9]. Strictly following the indications, meniscal transplantation can give good and predictable results [68]. 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 [71]. Patients with ACL tears treated non-operatively developed secondary meniscal lesions requiring delayed surgical management [52]. Delayed ACL reconstruction is associated with a greater incidence of concomitant medial meniscal and chondral injury [118].

Surgical Approach / Technique: Meniscal repair is a viable alternative to resection in many clinical situations, with success rates exceeding 80% when performed with anterior cruciate ligament reconstruction [16]. Clinical outcomes of patients that underwent meniscus repair were better than those that underwent meniscus resection with concurrent ACL reconstruction [61]. Repairs of the longitudinal posterior horn of the medial meniscus during an ACL reconstruction with nonweightbearing for 5 weeks can be performed with an equivalent high degree of clinical success for both repair techniques [117]. Complete healing of both menisci was confirmed arthroscopically 3 years postoperatively in a case of radial tears in the roots of the posterior horns of both the medial and lateral menisci combined with an anterior cruciate ligament tear [57]. Arthroscopic treatment of a symptomatic discoid lateral meniscus in childhood shows long-term efficacy [64]. Arthroscopic meniscus transplantation can achieve satisfying subjective and objective clinical outcomes, with a failure rate of 11% after 1–3 years of followup [73].

Implant Selection: Meniscal allograft, for proper indications, shows adequate outcomes as a salvage procedure [18]. Current practice guidelines for the ACL-deficient knee with single-compartment osteoarthritis include pathoanatomy, indications, contraindications, technical considerations, and clinical outcomes [19].

Adjuncts: There was no difference in outcomes in meniscal repair performed with biological augmentation using an MVP versus that performed concomitantly with ACL reconstruction [65]. Additional research is needed to ensure that biologic augmentation tools are used with appropriate clinical indications and to acknowledge that not all meniscus repairs can always heal [80].

Other Considerations: Long-term evaluation of ACL-reconstructed knees with concurrent successful meniscal repairs demonstrates a low rate of radiographic arthritis [5]. Patients with ACL reconstruction and meniscal resections do not exhibit decreased clinical outcomes at 2 years postoperatively [6]. 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 [17]. Knee meniscal repair has a success rate of approximately 80% in both men and women [67]. Meniscal allograft survival and patient-reported outcomes were associated with age, with lower outcomes in patients younger than 35 years and worse survival in patients older than 50 years [69]. Meniscectomy remains overused due to non-scientific factors like technical difficulty, cost, and patient preferences [82].

Complications

Osteoarthritis: At 10 to 20 years after diagnosis, 50% of patients with a diagnosed anterior cruciate ligament (ACL) or meniscus tear develop osteoarthritis with associated pain and functional impairment [2]. At 10-year follow-up, radiological signs of osteoarthritis are present in 53.5% of subjects following ACL reconstruction with a 4-strand hamstring autograft and accelerated rehabilitation [25]. Meniscectomy performed prior to or at the time of ACL reconstruction is identified as a risk factor for these radiological signs [25]. Similarly, chondral lesions present at the time of ACL reconstruction are identified as a risk factor for radiological signs of osteoarthritis at 10-year follow-up [25]. Meniscal and chondral pathology at the time of revision ACL reconstruction continues to have significant detrimental effects on patient-reported outcomes at 6 years after revision surgery [70]. Conversely, long-term evaluation of ACL-reconstructed knees with concurrent successful meniscal repairs demonstrates a low rate of radiographic arthritis [5].

Instability and Re-injury: A history of ACL reconstruction is a risk factor for further injury, with the highest risk occurring in the first year after reconstruction [120]. Ligament knee lesions are most probably the result of recent trauma [116]. Longitudinal lateral meniscal tears in ACL-deficient knees do not involve secondary meniscal pathology but derive from a primary recent injury [122]. The recent lateral meniscal lesion does not evolve in meniscal length and depth [122]. Clinical grading of instability has clarified the natural history of discoid lateral meniscus-associated tearing [24]. Recent studies have shed new light on the natural history of injury to the posterior cruciate ligament, as well as on its complex anatomy and functional mechanical behavior [121].

Other Considerations: Long-term subjective and objective results of a successful ACL reconstruction are affected by the status of the menisci and articular surface [12]. Eighty-three percent of menisci were symptom-free regardless of meniscal integrity after arthroscopic meniscal repair with the FasT-Fix during ACL reconstruction, though newly formed injuries may occur even in asymptomatic cases [14]. Good short-term clinical and anatomic outcomes are observed post-repair of meniscal lesions despite their chronic nature [15]. 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 [17]. Good long-term outcomes can be obtained in patients up to over 12 years after combined ACL reconstruction and meniscal repair [20]. Meniscal preservation with repair of radial tears results in improved short-term clinical outcomes, however, long-term outcomes remain unknown [21]. Patients with ACL reconstruction with meniscal resections do not exhibit decreased clinical outcomes at 2 years postoperatively [6]. Two-year improvements in patient-reported outcomes after meniscal allograft transplantation are predictive of sustained success at midterm and long-term follow-up, with significant correlations observed between 2-year outcomes and those at 5 to 10 and 10+ years [22]. Meniscus repair failure risk does not differ between men or women at mid-term follow up [72]. A history of meniscectomy shortens the expected career of a professional football player, whereas ACL reconstruction does not shorten the expected career of a professional football player [112]. 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; all existing studies on the natural history of untreated meniscus tears are at best case series with no comparative studies [23].

Recovery

Light activity (weeks): Evidence does not specify a discrete week range for light activity or driving; however, accelerated rehabilitation protocols are noted in the context of 10-year follow-up outcomes [25].

Full activity (months): Good short-term clinical and anatomic outcomes are observed post-repair of meniscal lesions despite their chronic nature [15], and good long-term outcomes can be obtained in patients up to over 12 years after combined anterior cruciate ligament reconstruction and meniscal repair [20]. Two-year improvements in patient-reported outcomes after meniscal allograft transplantation are predictive of sustained success at midterm and long-term follow-up, with significant correlations observed between 2-year outcomes and those at 5 to 10 and 10+ years [22].

Complete recovery / outcome plateau (months): 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 [2]. At 10-year follow-up, radiological signs of osteoarthritis were present in 53.5% of subjects following anterior cruciate ligament reconstruction with 4-strand hamstring autograft and accelerated rehabilitation [25]. The long-term subjective and objective results of a successful anterior cruciate ligament reconstruction are affected by the status of the menisci and articular surface [12]. Clinically useful positive predictive values for scintigraphic patterns in anterior cruciate ligament deficiency were found only for medial meniscus lesions when time since ACL rupture was more than 18 months [3], and only for local cartilage degeneration when markedly increased uptake was seen when time since ACL rupture was more than 4 months [3]. Meniscal repair is associated with a lower progression to knee osteoarthritis at approximately six years of followup compared to partial meniscectomy [126].

Rehabilitation protocol: The long-term evaluation of anterior cruciate ligament–reconstructed knees with concurrent successful meniscal repairs demonstrated a low rate of radiographic arthritis [5]. Magnetic resonance imaging is unsuitable for diagnosis of the healing process of a repaired meniscus [94].

Functional milestones: 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 [100]. A meniscal lesion at the time of anterior cruciate ligate tear was highly predictive for less favourable outcome following arthroscopically assisted anatomical single-bundle anterior cruciate ligament reconstruction using patellar tendon autograft [123]. In female patients who experienced an anterior cruciate ligament injury, a delay in surgery greater than 12 months is associated with a gradual increase in the risk of nonrepairable medial meniscal tear [124], and the risk becomes statistically significant after 24 months [124].

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 [23], and all existing studies on the natural history of untreated meniscus tears are at best case series with no comparative studies [23]. Clinical grading of instability has clarified the natural history of discoid lateral meniscus-associated tearing [24]. Meniscal preservation with repair of radial tears results in improved short-term clinical outcomes, however, long-term outcomes remain unknown [21]. The long-term survival rate of repaired menisci was 91% [94]. Meniscal allograft transplantation 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 [95]. Relapse of meniscal symptoms and arthrosis have not been observed in a patient with bilateral discoid medial menisci accompanied by distal arthrogryposis, although long-term follow-up is considered necessary [96]. At long-term follow-up greater than 8 years, shrinkage of transplanted fresh-frozen meniscal allografts progressed at 1 year postoperative [125], was on average mild [125], and was more prominent in the mid-body than in the anterior or posterior horn [125]. The short-term results of delayed meniscus transplantation were close to those of meniscectomy [127].

Key Evidence

• [L4] This ligamentous structure is an important differential diagnosis to symptoms usually referred to as meniscus pathology. (10.1016/j.arthro.2005.12.023)
• [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] Intra-articular abnormalities did not explain all scintigraphic patterns, and clinically useful positive predictive values were found only for medial meniscus lesions when time since ACL rupture was more than 18 months, and for local cartilage degeneration when markedly increased uptake was seen when time since ACL rupture was more than 4 months. (10.1007/s001670050203)
• [L4] Further studies are needed to define the relative importance of the individual histologic findings in the clinical setting of meniscus tear and repair. (10.1177/0363546506293700)
• [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)
• [L2] Patients with ACLR with meniscal resections do not exhibit decreased clinical outcomes at 2 years postoperatively. (10.1177/0363546515577364)
• [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)
• [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)
• [L4] Medial meniscus repair in the ACL-deficient knee is not contraindicated. (10.1007/s00167-006-0162-2)
• [L3] 1.5-Tesla MRI accurately diagnoses ACL and medial meniscal tears and can reliably complete the diagnostic workup following physical examination, particularly in young adults. (10.1186/s12891-021-04011-3)
• [L3] MR diagnosis of a partial ACL tear is difficult because various tear patterns may be seen, with many partial tears demonstrating MR features indistinguishable from complete ACL tear, mucoid ACL degeneration, or normal ACL. (10.1007/s00167-011-1617-7)
• [L3] The long-term subjective and objective results of a successful anterior cruciate ligament reconstruction are affected by the status of the menisci and articular surface. (10.1177/03635465000280040201)
• [L4] Medial meniscal ramp lesions were present in approximately 17% of patients undergoing ACL reconstruction, and less than one-half were diagnosed on preoperative MRI. (10.1177/0363546517704426)
• [L4] Eighty-three percent of menisci were symptom-free regardless of meniscal integrity, but newly formed injuries may occur even in asymptomatic cases. (10.1177/0363546509356977)
• [L4] The results found suggest good short-term clinical and anatomic outcomes post-repair of meniscal lesions, despite their chronic nature. (10.1007/s00167-013-2552-6)
• [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] 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)
• [L5] Meniscal allograft, for proper indications, shows adequate outcomes (for a salvage procedure). (10.1016/j.arthro.2015.02.042)
• [L5] This review discusses current practice guidelines for the ACL-deficient knee with single-compartment osteoarthritis, including pathoanatomy, indications, contraindications, technical considerations, and clinical outcomes. (10.1016/j.jisako.2024.100337)
• [L3] This study demonstrates that good long-term outcomes can be obtained in patients up to over 12 years after combined ACL reconstruction and meniscal repair. (10.1007/s00167-011-1501-5)
• [L1] Meniscal preservation with repair of radial tears results in improved short-term clinical outcomes, however, long-term outcomes remain unknown. (10.1016/j.arthro.2016.03.029)
• [L4] Two-year improvements in patient-reported outcomes after meniscal allograft transplantation are predictive of sustained success at midterm and long-term follow-up, with significant correlations observed between 2-year outcomes and those at 5 to 10 and 10+ years. (10.1016/j.arthro.2025.02.020)
• [L3] Clinical grading of instability has clarified the natural history of discoid lateral meniscus-associated tearing. (10.1007/s00167-023-07521-w)
• [L2] At 10-year follow-up, radiological signs of OA were present in 53.5% of subjects, with meniscectomy prior to or at the time of ACL reconstruction and chondral lesions at the time of ACL reconstruction identified as risk factors. (10.1007/s00167-012-2234-9)
• [L3] Jump direction significantly influenced knee biomechanics, suggesting that lateral jumps are the most dangerous of the stop-jumps. (10.1177/0363546505278696)
• [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)
• [L5] There were no differences in knee kinematics between the DB and SB-central techniques. (10.1177/0363546515611646)
• [L5] Surgical treatment of MMPRA allows restoration of physiological knee joint biomechanics. (10.1002/ksa.12465)
• [L5] Altering the normal ligament length resulted in measurable changes in knee kinematics and stability. (10.1007/s00167-011-1519-8)
• [L3] Knee biomechanics in the leg with ACLR were altered mainly in the sagittal plane during side-cutting compared with the contralateral leg. (10.1177/03635465221112940)
• [L4] No braces are currently available with biomechanical evidence that satisfies the requirements of applying correct anatomic joint forces that vary with the knee flexion angle. (10.1007/s00167-012-2048-9)
• [L5] This model can effectively analyze the biomechanical functions of the superficial and deep layers of the MCLs of knee joints. (10.1186/s13018-017-0566-3)
• [L5] The study established an experimental protocol to measure knee kinematics during weight-bearing flexion. (10.1016/j.arthro.2010.04.069)
• [L5] Conversely, fixation with the knee in flexion and an anterior tibial load best restored intact knee biomechanics. (10.1177/03635465000280040401)
• [L5] Both fixation protocols restored knee kinematics without predisposing either graft to failure. (10.1177/0363546507300822)
• [L4] The effective role of the anatomical double-bundle procedure in better restoring knee kinematics should be questioned in an in vivo model. (10.1177/0363546507305677)
• [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] Proper use of physical examination techniques requires understanding of the anatomy and biomechanical principles of the knee as well as the pathophysiology of the injuries. (10.5435/jaaos-d-15-00464)
• [L3] Kinematics of the anterior cruciate ligament injured knee did not change significantly after ligament reconstruction, but the functional results were satisfactory and knee laxity was diminished. (10.1177/03635465020300031001)
• [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)
• [L4] The position of an ACL graft is the most critical surgical variable because it has a direct effect on knee biomechanics and, ultimately, on clinical outcome. (10.1177/0363546505279922)
• [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)
• [L3] Knee kinematics derived from the OLR were reliable for asymptomatic and ACL-injured knees. (10.1186/s12891-019-2887-3)
• [L5] Knowledge of the biomechanical function of the anterolateral components is lacking, and further research is required to evaluate the influence of the anterolateral capsule on rotatory laxity of the knee. (10.1007/s00167-015-3616-6)
• [L4] The discoid meniscus lesion represents an atypical clinical entity in adults with no significant predictive value of clinical signs for diagnosis. (10.1007/s00167-008-0703-y)
• [L4] The presenting symptoms were due to a medial meniscus tear, while the accessory lateral meniscus was found incidentally. (10.1007/s00167-006-0093-y)
• [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] Anterior cruciate ligament mucoid degeneration needs to be more broadly known and properly diagnosed so that progress can be made in its management. (10.1007/s00167-011-1433-0)
• [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)
• [L3] Cartilage lesions exhibited a synovial fluid inflammatory profile distinct from ACL and meniscal injury at the time of knee arthroscopy, with ACL and meniscal injuries displaying a pro-inflammatory phenotype while more severe cartilage lesions were associated with a reduced presence of anti-inflammatory markers. (10.1177/03635465251381371)
• [L3] Patients with ACL tears treated non-operatively developed secondary meniscal lesions requiring delayed surgical management. (10.1007/s00167-018-5201-2)
• [L5] This sign can be a supportive finding for diagnosis and preoperative planning for meniscus injury. (10.1007/s00167-011-1441-0)
• [L2] Clinical examination by an experienced examiner using multiple meniscus tests is sufficient for a diagnosis of a meniscal tear. (10.1007/s00167-011-1636-4)
• [L4] A higher incidence of ligament and meniscal injuries was noted with higher-grade subtypes. (10.1016/j.jisako.2025.100921)
• [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] The meniscal pseudocyst is a new clinical sign characterized by a lump protruding from the joint line, most prominent at 45° of flexion, which has a complete correlation with meniscal tears requiring surgical intervention. (10.1177/03635465010290050301)
• [L4] Tears of the posterior horn of the medial meniscus may be underdiagnosed by intraoperative assessment using only an anterolateral portal view during ACL reconstruction. (10.1016/j.arthro.2014.12.003)
• [L4] The discoid medial meniscus remains a rare abnormality with significant associated morbidity. (10.1007/s00167-011-1487-z)
• [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)
• [L4] An arthroscopic classification system for discoid lateral menisci is proposed based on morphology and instability. (10.1016/j.arthro.2006.09.002)
• [L4] The results showed the long-term efficacy of arthroscopic treatment of a symptomatic discoid lateral meniscus. (10.1007/s00167-011-1440-1)
• [L3] There was no difference in outcomes in meniscal repair performed with biological augmentation using an MVP versus that performed concomitantly with ACL reconstruction. (10.1177/0363546516686968)
• [L2] These findings demonstrate that plain radiographs can be used to screen for and diagnose discoid lateral meniscus. (10.1007/s00167-016-3999-z)
• [L5] Knee meniscal repair has a success rate of approximately 80% in both men and women, and meniscal repair is a critical procedure for maintaining long-term knee health. (10.1016/j.arthro.2019.12.017)
• [L4] Strictly following the indications, meniscal transplantation can give good and predictable results. (10.1177/0363546510375399)
• [L3] Both meniscal allograft survival and patient-reported outcomes were associated with age, with lower outcomes in patients younger than 35 years and worse survival in patients older than 50 years. (10.1007/s00167-020-06276-y)
• [L3] Meniscal and chondral pathology at the time of revision ACL reconstruction has continued significant detrimental effects on patient-reported outcomes at 6 years after revision surgery. (10.1177/03635465231151389)
• [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)
• [L3] Meniscus repair failure risk does not differ between men or women at mid-term follow up. (10.1016/j.arthro.2019.09.030)
• [L4] Arthroscopic meniscus transplantation can achieve satisfying subjective and objective clinical outcomes, with a failure rate of 11% after 1–3 years of followup, as documented by second-look arthroscopy. (10.1007/s00167-011-1572-3)
• [L4] However, the MRI did not reveal normal menisci in all cases. (10.1002/ksa.12724)
• [L4] Meniscal tears are commonly seen in each Schatzker classification, with longitudinal tears being the most common pattern. (10.1186/s13018-021-02265-0)
• [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)
• [L4] The classification system used to report Kaplan fiber injury was associated with low inter-rater reliability, and the presence of Kaplan fiber injury was not associated with other injuries commonly observed in conjunction with ACL tear. (10.1007/s00167-021-06730-5)
• [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)
• [L5] Magnetic resonance imaging is the best method for accurately evaluating these lesions, as it can demonstrate all of the visible features of meniscal cysts. (10.1177/03635465990270021901)
• [L5] Additional research is needed to shed more light in this fascinating microworld, and we need to ensure that all these amazing tools are used with appropriate clinical indications and that we acknowledge that not all menisci repairs can always heal. (10.1016/j.arthro.2021.08.017)
• [L4] This study demonstrated that non-operative treatment provided symptomatic relief in most patients with the degenerative posterior root tear of the medial meniscus. (10.1007/s00167-009-0891-0)
• [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)
• [L4] These findings provide valuable insights into the nuanced nature of synovial inflammation induced by various meniscal tear classifications and contribute to the development of new adjunctive therapeutic agents in the management of synovitis. (10.1186/s12891-024-07491-1)
• [L3] All 24 knees exhibited MRI abnormalities with an unexpectedly high number of pathological changes in the menisci and ligaments developing in the long term. (10.1186/s12891-015-0633-z)
• [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)
• [L1] Arthroscopic partial meniscectomy should not be proposed as a first line of treatment for degenerative meniscus lesions and should only be considered after non-operative management has failed. (10.1007/s00167-016-4407-4)
• [L3] The clinical relevance of this finding is that MRI contributes to enhancing the diagnostic accuracy of an unhealed meniscal repair when there are limited clinical signs of meniscal pathology. (10.1007/s00167-019-05523-1)
• [L4] This study shows a high prevalence of articular cartilage damage as defined by the Outerbridge classification in patients undergoing arthroscopic surgery for meniscal pathology. (10.1016/j.arthro.2012.02.029)
• [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)
• [L4] The type and location of these tears differ from those seen in ACL-deficient knees, which is useful for predicting surgical procedures. (10.1177/0363546506287939)
• [L3] MRI is not always useful in predicting reparability of symptomatic isolated lateral semilunar meniscus tears, and most of the symptomatic cases with normal MRI were reparable. (10.1007/s00167-002-0280-4)
• [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)
• [L3] The long-term survival rate of repaired menisci was 91%, and magnetic resonance imaging is unsuitable for diagnosis of the healing process of a repaired meniscus. (10.1177/03635465990270011001)
• [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)
• [Case_report] Relapse of meniscal symptoms and arthrosis have not been observed in this patient, although long-term follow-up is considered necessary. (10.1007/s00167-006-0178-7)
• [L3] The diagnostic accuracy of MRI for multiple ligament knee injuries largely varied among knee structures, with many at risk of misdiagnosis, especially posterolateral corner, meniscal, and chondral lesions. (10.1177/03635465221145697)
• [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)
• [L4] MRI is successful in determining the presence or absence of tears in discoid menisci; however, its ability to determine the tear type is questionable. (10.1007/s00167-013-2371-9)
• [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 degree of ligament injury patterns and the side of the injured collateral ligament influenced the type and incidence of meniscal damage. (10.1007/s00167-022-07064-6)
• [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)
• [L4] We recommend nonoperative treatment of anterior horn tears noted on MRI among patients without mechanical symptoms and whose clinical examination is inconsistent with the presence of a pathologic meniscal condition. (10.1177/03635465020300020701)
• [L3] Both treatment types were associated with new cartilage lesions, suggesting that meniscal injury itself may be a key contributor to cartilage degeneration. (10.1002/ksa.70369)
• [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)
• [L2] Due to the significantly higher rate of prognostically advantageous meniscal repair, the recommendation for an ACL reconstruction within 6 months after trauma was made to preserve the meniscus and reduce the risk of developing OA. (10.1007/s00167-015-3830-2)
• [L4] The anterior meniscofemoral ligament of the medial meniscus is a rare anomaly that is often unrecognized and underreported because MRI rarely detects it and it may be obscured during arthroscopy. (10.1177/0363546503261712)
• [L2] Development of new cartilage lesions was evident after 2-year follow-up in patients with arthroscopic ACLR as detected by MR imaging. (10.1007/s00167-016-4153-7)
• [L5] The authors argue that evaluating the usefulness of meniscectomy is flawed due to insufficient stratification of meniscal tear characteristics, and that clinical practice guidelines may be flawed if they recommend against treatments that benefit specific patient subgroups despite Level I evidence showing safety and efficacy. (10.1016/j.arthro.2014.03.016)
• [L5] Arthroscopic partial meniscectomy should not be proposed as a first-line treatment for degenerative meniscus lesions; non-operative treatment should always be started first, with surgery only envisaged after its failure. (10.1007/s00167-017-4458-1)
• [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] A history of meniscectomy, but not ACL reconstruction, shortens the expected career of a professional football player. (10.1177/0363546509349035)
• [L4] Non-surgical treatment for acute medial meniscus posterior root tear did not result in any significant change in clinical outcomes from the initial to the final follow-up. (10.1007/s00167-023-07444-6)
• [L4] Nonoperative management resulted in high rates of residual knee instability, increased risk of meniscal tears, and comparatively low rates of return to sports. (10.1177/0363546521990817)
• [L5] Initial nonoperative management of degenerative meniscal tears is worth a try. (10.1016/j.arthro.2019.11.128)
• [L2] Ligament knee lesions are most probably the result of recent trauma. (10.1177/0363546506290189)
• [L3] Repairs of the longitudinal posterior horn of the medial meniscus during an anterior cruciate ligament reconstruction with nonweightbearing for 5 weeks can be performed with an equivalent high degree of clinical success for both repair techniques. (10.1177/03635465030310063101)
• [L2] Delayed ACL reconstruction is associated with a greater incidence of concomitant medial meniscal and chondral injury and should be considered when trialling non‐operative management for ACL rupture. (10.1002/ksa.70002)
• [L2] A history of anterior cruciate ligament reconstruction is a risk factor for further injury, with the highest risk in the first year after reconstruction. (10.1177/03635465010290021301)
• [L4] Recent studies have shed new light on the natural history of injury to the posterior cruciate ligament, as well as on its complex anatomy and functional mechanical behavior, and this new information is likely to alter the way that orthopaedic surgeons have traditionally treated injuries to this structure. (10.2106/00004623-199309000-00014)
• [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)
• [L4] A meniscal lesion at the time of ACL tear was highly predictive for less favourable outcome. (10.1007/s00167-012-2001-y)
• [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)
• [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)
• [L1] Meniscal repair is associated with a lower progression to knee osteoarthritis at approximately six years of followup compared to partial meniscectomy. (10.1007/s00167-023-07600-y)
• [L3] The short-term results of delayed meniscus transplantation were close to those of meniscectomy. (10.1177/0363546514541653)

See Also

• Anterior Cruciate Ligament
• Biomechanics
• Anatomy

References

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