The knee meniscus: Structure–function, pathophysiology, current repair techniques, and prospects for regeneration

The meniscus has long been appreciated as a source of knee symptoms and disability. In fact, through much of the 20 th century total meniscectomy was performed relatively frequently for patients with persistent, disabling mechanical knee symptoms. The procedure relieved mechanical symptoms but at a cost: Total meniscectomy was associated with accelerated degenerative radiographic changes, establishing the importance of the meniscus in the pathogenesis of osteoarthritis.1 -3 Biomechanical studies clarified these clinical observations. The meniscus distributes substantial mechanical load throughout the tibiofemoral joint surfaces that would otherwise be transmitted directly and focally to the weight-bearing portions of the femur and tibia. Damage to or resection of the meniscus disrupts this load sharing function, leading to excess loading of cartilage and subchondral bone and attendant changes of osteoarthritis.1 ,

Meniscus is a vital functional unit in knee joint. It acts as a lubricating structure, a nutrient transporting structure, as well as shock absorber during jumping, twisting and running and offers stability within the knee joint. It helps in load distribution, in bearing the tensile hoop stresses and balancing by providing a cushion effect between hard surfaces of two bones. Meniscus may be injured in sports, dancing, accident or any over stressed condition. Any meniscal lesion can lead to a gradual development of osteoarthritis or erosion of bone contact surface due to disturbed load and contact stress distribution caused by injury/pain. Once injured, the possibilities of self-repair are rare in avascular region of meniscus, due to lack of blood supply in avascular region. Meniscus has vascular and avascular regions in structure. Majority of the meniscus parts turn avascular with increase in age.Purpose of this review is to highlight advances in meniscus repair with special focus on tissue engineering using textile/fiber based scaffolds, as well as the recent technical advances in scaffolds for meniscus recon- struction/ regeneration treatment.

Arthroscopic meniscectomy

To evaluate the biomechanical effect of horizontal, vertical, and cruciate suture repairs and partial meniscectomy on contact mechanics of dog stifles. Ex vivo experimental study. Cadaveric canine stifles (n=24). Simulated bucket handle medial meniscal tears were created in cadaveric dog stifles. Tears were treated with 1 of 3 suture repair techniques or partial meniscectomy. Instantaneous contact area (CA), mean contact pressure (MCP), and peak contact pressure (PCP) measurements were recorded with a pressure sensing system. CA, MCP, and PCP for intact stifles (control), stifles with simulated tears, and stifles after treatment were recorded and compared using 1-way repeated measures ANOVA. Stifles with bucket handle tears had significantly decreased CA, increased MCP and increased PCP when compared with control. All meniscal repair techniques reestablished normal contact mechanics. When comparing meniscal repair and partial meniscectomy, stifles with partial meniscectomy had approximately 35% lower CA, 57% higher MCP, and 55% higher PCP than stifles undergoing repair. Contact mechanics obtained from each repair technique were mechanically superior to partial meniscectomy. Performing meniscal repair instead of partial meniscectomy in dogs with select meniscal tears may mitigate the development of degenerative joint disease. Criteria for selection of candidates for meniscal repair should be confirmed with future studies. Based on this ex-vivo model, meniscal repair will restore normal contact mechanics. Consideration should be given to meniscal repair as treatment for peripheral meniscal tears located in the vascular zone if the meniscal parenchyma is normal.

Engineering Stem and Stromal Cell Therapies for Musculoskeletal Tissue Repair.

Meniscal Repair Versus Partial Meniscectomy: A Systematic Review Comparing Reoperation Rates and Clinical Outcomes

Objectives:Recent studies have described an increased risk of osteoarthritis (OA) following ACL reconstruction (ACLR). Systematic reviews have suggested that meniscal pathology, which occurs in up to 60% of patients with ACL injury, increases this risk. The purpose of this study was to determine the influence of lateral meniscus tears and repair versus partial lateral meniscectomy on the risk of OA in patients following ACLR.Methods:All patients who underwent primary autograft or allograft bone-patellar tendon-bone (BPTB) transtibial ACLR by a single surgeon between 1999-2019, were identified. Revision ACLR, multi-ligamentous reconstructions, and patients with less than 2-year imaging follow-up were excluded. Patients with lateral meniscus pathology at the time of ACLR were identified and treatment (e.g. lateral meniscectomy or lateral meniscus tear) was extracted. OA was defined at follow-up as Kellgren-Lawrence (KL) grade III-IV on plain radiographs. Chi-square tests assessed differences in incidence rates (p<0.05).Results:A consecutive series of 113 patients (57 males, 56 females; age 35.7±11.9 years) with BPTB ACLR were included. The mean follow-up was 9±5 years. The prevalence of lateral meniscus tears was 60.2% (68/113) and the prevalence of lateral compartment OA at follow-up was 14% (16/113) Patients with a lateral meniscus tear were 4.7 times more likely to develop OA compared to patients with no lateral meniscus tear. 20.6% of patients (14/68) with lateral meniscus tear developed lateral OA compared to 4.4% of patients (2/45) without lateral meniscus tear (p=0.0158). Patients who underwent lateral meniscal repair (n=16) had significantly lower prevalence of OA (0/16) compared to patients who underwent lateral meniscectomy (14/52) (p=0.0196).Conclusions:At nine-year follow-up, patients with a lateral meniscus tear at time of ACLR were more likely to develop OA compared to patients with no lateral meniscus tear and patients treated with partial meniscectomy had higher prevalence of OA compared to those treated with meniscus repair. In patients who require ACLR, care should be taken in evaluating and treating the lateral meniscus to decrease the likelihood of the development of OA. We believe lateral meniscal repair is essential for lateral meniscus tears at the time ACL reconstruction to help avoid development of OA.Figure 1.

Multi-ligament knee injuries (MLKIs) are rare and complex knee lesions and are potentially associated with intra-articular injuries, especially meniscal tears. Understanding the meniscal tear patterns involved in MLKI can help the orthopedic surgeon treat these complex injuries. The purpose of this study was to describe the incidence, classification, and treatment of meniscal injuries in a cohort of patients with MLKIs and carry out an updated review of the evidence available. Descriptive retrospective study. Patients with a history of reconstructive surgery for MLKI performed between 2013 and 2023 were included. Informed consent was obtained from all patients included in the study. Patient demographics, magnetic resonance imaging (MRI) study, and operative reports were reviewed. Groups were then formed based on ligament injury patterns. Meniscal tears were identified by MRI and through diagnostic arthroscopy for each patient. The association between meniscal lesions and injury patterns was calculated through Fisher's exact test. Agreement between the presence of meniscal tear on MRI and in diagnostic arthroscopy was measured using the kappa test. The sensitivity and specificity of MRI were calculated. We inferred the presence of a meniscal tear by injury pattern using the Agresti-Coull confidence interval. For the statistical analysis, a significance of 5% and a confidence interval of 95% were considered. Seventy patients with MLKIs were included, with a mean age of 30.69years (SD 10.65). Forty-seven patients had meniscal lesions (67.1%). Of them, 6 had only medial meniscus tears, 31 had only lateral meniscus tears, and 10 had lesions of both menisci, comprising 57 meniscal lesions in total. An anterior cruciate ligament (ACL) + medial collateral ligament/posteromedial corner (MCL/PMC) was the most common injury pattern (52.86% of all patients). Of these 37 patients, 78.38% had meniscal injuries, and most of them (68.97%) were only lateral meniscus injuries. The odds ratio (OR) of having a meniscal tear when having an ACL + medial-side injury was 4.83 (95% CI; 0.89-26.17). Patients with ACL + lateral-side injury pattern had meniscal tears in 42.86%. The lateral meniscus was involved in 100% of these patients. 62.5% of medial meniscus injuries were treated by meniscal repair, and 37.5% by partial meniscectomy. 58.54% of lateral meniscus injuries were treated by meniscal repair, and 39.02% by partial meniscectomy. Agreement calculated using the kappa test between MRI and diagnostic arthroscopy for medial meniscal lesions was 78.57%, and for lateral meniscal lesions was 84.29%. The ligament injury pattern and the side of the injured collateral ligament influenced the incidence and laterality of meniscal damage. ACL + medial-side injuries were shown to have significantly greater meniscal damage compared to other injury patterns.It is crucial to have a high index of suspicion, obtain a high-quality MRI, and arthroscopically evaluate any possible meniscal lesions in MLKIs.

Meniscal repair and regeneration: Current strategies and future perspectives

Stem Cell and Tissue Engineering Applications in Orthopaedics and Musculoskeletal Medicine

The Cost-Effectiveness of Meniscal Repair Versus Partial Meniscectomy in the Setting of Anterior Cruciate Ligament Reconstruction

Background: Meniscal tears in the avascular region are thought to rarely heal and are a considerable challenge to treat. Although the therapeutic effects of a pulsed electromagnetic field (PEMF) have been extensively studied in a variety of orthopaedic disorders, the effect of a PEMF on meniscal healing has not been reported. Hypothesis: PEMF treatment would promote meniscal healing and prevent osteoarthritis progression. Study Design: Controlled laboratory study. Methods: A total of 72 twelve-week-old male Sprague-Dawley rats with full-thickness longitudinal medial meniscal tears in the avascular region were divided into 3 groups: control (Gcon), treatment with a classic signal PEMF (Gclassic), and treatment with a high–slew rate signal PEMF (GHSR). Macroscopic observation and histological analysis of the meniscus and articular cartilage were performed to evaluate the meniscal healing and progression of osteoarthritis. The synovium was harvested for histological and immunofluorescent analysis to evaluate the intra-articular inflammation. Meniscal healing, articular cartilage degeneration, and synovitis were quantitatively evaluated according to their scoring systems. Results: Dramatic degenerative changes of the meniscus and articular cartilage were noticed during gross observation and histological evaluation in Gcon at 8 weeks. However, the menisci in the 2 treatment groups were restored to normal morphology, with a smooth surface and shiny white color. Particularly, the HSR signal remarkably enhanced the fibrochondrogenesis and accelerated the remodeling process of the regenerated tissue. The meniscal healing scores of the PEMF treatment groups were significantly higher than those in Gcon at 8 weeks. Specifically, the HSR signal showed a significantly higher meniscal repair score than did the classic signal at week 8 (P < .01). Additionally, the HSR signal significantly downregulated the secretion levels of interleukin 1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) in the meniscus and synovium as compared with the control group. When compared with the 2 treatment groups, Gcon had significantly higher degeneration scores (Gcon vs Gclassic, P < .0001; Gcon vs GHSR, P < .0001). The HSR signal also exhibited significantly lower synovitis scores compared with the other two groups (Gcon vs Gclassic, P < .0001; Gclassic vs GHSR, P = .0002). Conclusion: A PEMF promoted the healing of meniscal tears in the avascular region and restored the injured meniscus to its structural integrity in a rat model. As compared with the classic signal, the HSR signal showed increased capability to promote fibrocartilaginous tissue formation and modulate the inflammatory environment, therefore protecting the knee joint from posttraumatic osteoarthritis development. Clinical Relevance: Adjuvant PEMF therapy may offer a new approach for the treatment of meniscal tears attributed to the enhanced meniscal repair and ameliorated osteoarthritis progression.

Chondrocyte apoptosis and regional differential expression of nitric oxide in the medial meniscus following partial meniscectomy

The long-term effects of hyaluronan during development of osteoarthritis following partial meniscectomy in a rabbit model

PurposeThis study aimed to evaluate and compare the time required to return to sports (RTS) after surgery, the rate of revision surgery and the time required for RTS after revision surgery in elite athletes undergoing meniscal repair or partial meniscectomy, particularly analysing the difference between medial and lateral menisci. It was hypothesised that both procedures would entail similar, high rates of RTS, with the lateral meniscus exhibiting higher potential healing postprocedure compared to the medial meniscus.MethodsA systematic review was conducted based on the PRISMA guidelines. Quality assessment of the systematic review was performed using the AMSTAR-2 checklist. The following search terms were browsed in the title, abstract and keyword fields: ‘meniscus’ or ‘meniscal’ AND ‘tear,’ ‘injury’ or ‘lesion’ AND ‘professional,’ ‘elite’ or ‘high-level’ AND ‘athletes,’ ‘sports,’ ‘sportsman,’ ‘soccer,’ ‘basketball,’ ‘football’ or ‘handball’. The resulting measures extracted from the studies were the rate of RTS, level of RTS, complications, revision surgery and subsequent RTS, Tegner, International Knee Documentation Committee (IKDC) and Visual Analogue Scale (VAS).ResultsIn this study, the cohort consisted of 421 patients [415 (98.6%) men and 6 (1.4%) women] with a mean age of 23.0 ± 3.0 years. All patients were elite athletes in wrestling, baseball, soccer, rugby or handball. While 327 (77.7%) patients received partial meniscectomy at a mean age of 23.3 ± 2.6 years, 94 (22.3%) patients received meniscal repair at a mean age of 22.1 ± 4.0 years. After partial meniscectomy, 277 patients (84.7%) returned to their competitive sports activity and 256 (78.3%) returned to their pre-injury activity levels. A total of 12 (3.7%) patients required revision surgery because of persistent pain [5 (1.5%) patients], chondrolysis [2 (0.7%) patients] or both chondrolysis and lateral instability [5 (1.5%) patients]. Ten (83.3%) of the twelve patients had involvement of the lateral meniscus, whereas the location of injury was not specified in the remaining two patients. After revision surgery, all patients (100%) resumed sports activity. However, after meniscal repair, 80 (85.1%) athletes returned to their competitive sports activity and 71 (75.5%) returned to their pre-injury activity levels. A total of 16 (17.0%) patients required partial meniscectomy in cases of persistent pain or suture failure. Of these, 4 (25%) patients involved lateral and medial menisci each and 8 (50%) patients were not specified. After revision surgery, more than 80.0% of the patients (13) resumed sports activity.ConclusionsIn elite athletes with isolated meniscal injury, partial meniscectomy and meniscal suture exhibited similar rates of RTS and return to pre-injury levels. Nonetheless, athletes required more time for RTS after meniscal repair and exhibited an increased rate of revision surgery associated with a reduced rate of RTS after the subsequent surgery. For lateral meniscus tears, meniscectomy was associated with a high rate of revision surgery and risk of chondrolysis, whereas partial medial meniscectomy allowed for rapid RTS but with the potential risk of developing knee osteoarthritis over the years. The findings of this systematic review suggested a suture on the lateral meniscus in elite athletes because of the high healing potential after the procedure, the reduced risk of developing chondrolysis and the high risk of revision surgery after partial meniscectomy. Furthermore, it is important to evaluate several factors while dealing with the medial meniscus. If rapid RTS activity is needed, a hyperselective meniscectomy is recommended; otherwise, a meniscal suture is recommended to avoid accelerated osteoarthritis.Level of evidenceLevel IV.Study registrationPROSPERO-CRD42022351979 (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=351979).