The Interplay of Biomechanical and Biological Changes Following Meniscus Injury

Correlation of meniscus tear type with synovial inflammation and the therapeutic potential of docosapentaenoic acid

BACKGROUND

Synovitis, characterized by inflammation of the synovial membrane, is commonly induced by meniscus tears. However, significant differences in inflammatory responses and the key inflammatory mediators of synovium induced by different types of meniscal tears remain unclear.

METHODS

Magnetic resonance imaging (MRI) was employed to identify the type of meniscus tear, and the quantification of synovial inflammation was assessed through H&E staining assay. Transcription and expression levels of IL-1β and IL-6 were evaluated using bioinformatics, ELISA, RT-qPCR, and IHC of CD68 staining assays. The therapeutic potential of Docosapentaenoic Acid (DPA) was determined through network pharmacology, ELISA, and RT-qPCR assays. The safety of DPA was assessed using colony formation and EdU staining assays.

RESULTS

The results indicate that both IL-1β and IL-6 play pivotal roles in synovitis pathogenesis, with distinct expression levels across various subtypes. Among tested meniscus tears, oblique tear and bucket handle tear induced the most severe inflammation, followed by radial tear and longitudinal tear, while horizontal tear resulted in the least inflammation. Furthermore, in synovial inflammation induced by specific meniscus tears, the anterior medial tissues exhibited significantly higher local inflammation than the anterior lateral and suprapatellar regions, highlighting the clinical relevance and practical guidance of anterior medial tissues' inflammatory levels. Additionally, we identified the essential omega-3 fatty acid DPA as a potential therapeutic agent for synovitis, demonstrating efficacy in blocking the transcription and expression of IL-1β and IL-6 with minimal side effects.

CONCLUSION

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.

Functional testing following isolated meniscus repair may help to identify patients who need additional physical therapy prior to a return to activity

OBJECTIVES

Functional testing (FT), commonly used to evaluate dynamic knee function and provide objective information about how well a patient, has progressed in rehabilitation following an anterior cruciate ligament (ACL) reconstruction. The purpose of the study was to determine whether a functional test could be used as an assessment tool for return to activity following isolated meniscus repair.

METHODS

The results of FT completed between 80 and 150 days post-operation (representing 4-months post-operative) in isolated meniscal repair patients were analysed for the involved limb, uninvolved limb, and limb symmetry index (LSI). Involved limb performance and LSI on FT were also recorded for a matched cohort of patients who underwent an isolated ACL reconstruction between 151 and 220 days post-operation (representing 6-months post-operative). The meniscus cohort was compared to the ACL cohort.

RESULTS

The meniscus cohort (n ​= ​26) performed well (LSI of 88% or better) on all functional test exercises, including all hop tests. There were patients in the meniscus cohort who did not achieve 90% LSI on the FT at 4 months. There was no statistically significant difference in any of the tests between the meniscus and ACL (n ​= ​39) cohorts.

CONCLUSION

A majority of isolated meniscal repair patients perform well on FT by 4 months post-operatively and similar to patients undergoing isolated ACL reconstruction at 6 months post-operatively. Not all patients performed well on FT at 4 months post-operatively; however so, there may be a role for FT in isolated meniscal repair patients, and those patients may need further physical therapy prior to a return to sports.

LEVEL OF EVIDENCE

III; Retrospective cohort study.

LEVEL OF EVIDENCE

IV.

Increased lateral femoral condyle ratio measured by MRI is associated with higher risk of solitary meniscus injury

Background: Past studies found that an increased lateral femoral condyle ratio is associated with anterior cruciate ligament injuries, but it is not clear if there is a link between MRI-measured lateral femoral condyle ratios and meniscal injuries. MRI provides a more accurate selection of measurement planes. Compared to X-rays, it further reduces data errors due to non-standard positions. Objective: To study the relationship between knee bone morphology and Solitary meniscal injuries by MRI. Methods: A total of 175 patients were included in this retrospective case-control study, including 54 cases of pure medial meniscus injury, 44 cases of pure lateral meniscus injury as the experimental group, and 77 control subjects. MRI images were used to measure the femoral notch width, femoral condylar width, femoral notch width index, lateral femoral condylar ratio (LFCR), posterior tibial slope, medial tibial plateau depth, and meniscus slope. In addition, carefully check for the presence of specific signs such as bone contusions and meniscal extrusions. Comparing the anatomical differences in multiple bone morphologies between the two groups, a stepwise forward multifactorial logistic analysis was used to identify the risk factors for Solitary meniscal injuries. Finally, ROC curves were used to determine the critical values and best predictors of risk factors. Results: MTS, LTS, and LFCR ended up as independent risk factors for meniscus injury. Among all risk factors, LFCR had the largest AUC of 0.781 (0.714-0.848) with a threshold of 72.75%. When combined with MTS (>3.63°), diagnostic performance improved with an AUC of 0.833 (0.774-0.892). Conclusion: Steep medial tibial plateau slope, steep lateral tibial plateau slope angle, and deep posterior lateral femoral condyles on MRI are independent risk factors for meniscal injuries. In patients with knee discomfort with the above imaging findings (X-ray, MRI), we should suspect and carefully evaluate the occurrence of meniscal injuries. It not only provides a theoretical basis to understand the mechanism of meniscus injury but also provides theoretical guidance for the prevention of meniscus injury and the development of intervention measures. Level of evidence III.

Engineering approaches for RNA-based and cell-based osteoarthritis therapies

Osteoarthritis (OA) is a chronic, debilitating disease that substantially impairs the quality of life of affected individuals. The underlying mechanisms of OA are diverse and are becoming increasingly understood at the systemic, tissue, cellular and gene levels. However, the pharmacological therapies available remain limited, owing to drug delivery barriers, and consist mainly of broadly immunosuppressive regimens, such as corticosteroids, that provide only short-term palliative benefits and do not alter disease progression. Engineered RNA-based and cell-based therapies developed with synthetic chemistry and biology tools provide promise for future OA treatments with durable, efficacious mechanisms of action that can specifically target the underlying drivers of pathology. This Review highlights emerging classes of RNA-based technologies that hold potential for OA therapies, including small interfering RNA for gene silencing, microRNA and anti-microRNA for multi-gene regulation, mRNA for gene supplementation, and RNA-guided gene-editing platforms such as CRISPR-Cas9. Various cell-engineering strategies are also examined that potentiate disease-dependent, spatiotemporally regulated production of therapeutic molecules, and a conceptual framework is presented for their application as OA treatments. In summary, this Review highlights modern genetic medicines that have been clinically approved for other diseases, in addition to emerging genome and cellular engineering approaches, with the goal of emphasizing their potential as transformative OA treatments.

Inflammatory synovial biomarkers and state of the tibiofemoral joint in the post-surgical settings: a narrative review

Background and Objective

Knee surgery attempts to restore the native biomechanics of the knee, improve stability, and decrease the progression of osteoarthritis (OA). However, despite improvements in surgical techniques, tissue degradation and OA are common after knee surgery, occurring in higher rates in surgical knees compared to non-surgical knees. The aim of this study is to analyze previous literature to determine which synovial fluid biomarkers contribute to knee tissue degradation and decrease patient outcomes in the post-surgical setting of the knee.

Methods

A narrative review of relevant literature was performed in July 2023. Studies reporting on synovial biomarkers associated with the post-surgical knee were included.

Key Content and Findings

The literature reported that proinflammatory synovial biomarkers cause cartilage degradation and turnover which eventually leads to OA. The associated biomarkers are typically present prior to physical symptoms so understanding which one's correlate to OA is important for potential therapeutic treatments in the future. Studying the preoperative, early postoperative, and late postoperative synovial biomarkers will allow physicians to develop an improved understanding of how these biomarkers progress and correlate to knee tissue degradation and OA. This understanding could lead to further developments into potential treatment options. Research into inhibiting or reversing these inflammatory biomarkers to slow the progression of knee tissue degradation has already begun and has reported some promising results but is currently limited in scope.

Conclusions

Synovial fluid biomarkers in the post-surgical knee setting may contribute to decreased patient outcomes and the progression of knee tissue degradation. There is no current consensus on which of these biomarkers are the most detrimental or associated with decreased patient outcomes. With an improved understanding of the individual biomarkers, potential personalized therapeutic treatment could be used by physicians in the future to improve patient outcomes after surgery.

Allografts for partial meniscus repair: an in vitro and ex vivo meniscus culture study

The purpose of this study was to evaluate the treatment potential of a human-derived demineralized scaffold, Spongioflex® (SPX), in partial meniscal lesions by employing in vitro models. In the first step, the differentiation potential of human meniscal cells (MCs) was investigated. In the next step, the ability of SPX to accommodate and support the adherence and/or growth of MCs while maintaining their fibroblastic/chondrocytic properties was studied. Control scaffolds, including bovine collagen meniscus implant (CMI) and human meniscus allograft (M-Allo), were used for comparison purposes. In addition, the migration tendency of MCs from fresh donor meniscal tissue into SPX was investigated in an ex vivo model. The results showed that MCs cultured in osteogenic medium did not differentiate into osteogenic cells or form significant calcium phosphate deposits, although AP activity was relatively increased in these cells. Culturing cells on the scaffolds revealed increased viability on SPX compared to the other scaffold materials. Collagen I synthesis, assessed by ELISA, was similar in cells cultured in 2D and on SPX. MCs on micro-porous SPX (weight >0.5 g/cm3) exhibited increased osteogenic differentiation indicated by upregulated expression of ALP and RUNX2, while also showing upregulated expression of the chondrogen-specific SOX9 and ACAN genes. Ingrowth of cells on SPX was observed after 28 days of cultivation. Overall, the results suggest that SPX could be a promising biocompatible scaffold for meniscal regeneration.

Post-traumatic osteoarthritis: epidemiology, pathogenesis, clinical picture, approaches to pharmacotherapy

Post-traumatic osteoarthritis (PTOA) is an inflammatory and degenerative disease that occurs as a result of the joint structures injury. It is a common pathology, accounting for approximately 12% of all cases of osteoarthritis (OA). PTOA often occurs in people of young productive age, progresses rapidly, causing chronic pain and increasing dysfunction. Individuals undergoing joint replacement for PTOA are, on average, 10 years younger than those with primary OA. The time interval from the moment of injury to the onset of typical PTOA radiological signs varies widely – from 1 year to 15–20 years.The main injuries that cause PTOA are intra-articular fractures, anterior cruciate ligament injuries, meniscus rupture and dislocation of the patella of the knee joint, joint dislocations with damage to the ligamentous apparatus of the ankle and shoulder joints.The pathogenesis of PTOA is determined by chronic inflammation accompanied by macrophage activation, hyperproduction of cytokines, primarily interleukin (IL) 1â, chemokines and growth factors, progressive destruction of joint tissue and degenerative changes (fibrosis, neoangiogenesis, osteophytosis).Pathogenetic treatment of PTOA, which would stop the progression of the disease, has not been developed. The possibility of using inhibitors of IL1â, IL6, inhibitors of tumor necrosis factor á, glucocorticoids, hyaluronic acid, autologous cell based therapy is under study. The control of pain and inflammation in PTOA requires the prescription of traditional drugs that are widely used in the practice of managing patients with primary OA. In particular, the use of symptomatic delayed-acting agents, such as the injectable form of chondroitin sulfate, seems to be appropriate.