The Importance of the Knee Joint Meniscal Fibrocartilages as Stabilizing Weight Bearing Structures Providing Global Protection to Human Knee-Joint Tissues

Abstract

The aim of this study was to review aspects of the pathobiology of the meniscus in health and disease and show how degeneration of the meniscus can contribute to deleterious changes in other knee joint components. The menisci, distinctive semilunar weight bearing fibrocartilages, provide knee joint stability, co-ordinating functional contributions from articular cartilage, ligaments/tendons, synovium, subchondral bone and infra-patellar fat pad during knee joint articulation. The meniscus contains metabolically active cell populations responsive to growth factors, chemokines and inflammatory cytokines such as interleukin-1 and tumour necrosis factor-alpha, resulting in the synthesis of matrix metalloproteases and A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS)-4 and 5 which can degrade structural glycoproteins and proteoglycans leading to function-limiting changes in meniscal and other knee joint tissues. Such degradative changes are hall-marks of osteoarthritis (OA). No drugs are currently approved that change the natural course of OA and translate to long-term, clinically relevant benefits. For any pharmaceutical therapeutic intervention in OA to be effective, disease modifying drugs will have to be developed which actively modulate the many different cell types present in the knee to provide a global therapeutic. Many individual and combinatorial approaches are being developed to treat or replace degenerate menisci using 3D printing, bioscaffolds and hydrogel delivery systems for therapeutic drugs, growth factors and replacement progenitor cell populations recognising the central role the menisci play in knee joint health.

Glycosaminoglycan and Proteoglycan Biotherapeutics in Articular Cartilage Protection and Repair Strategies: Novel Approaches to Visco‐supplementation in Orthobiologics

“…[412] Intra-articular injections of MSCs in sheep OA models retards the progression of OA and promotes repair of 60 mm full thickness cartilage defects [413] and stimulates cartilage regeneration in a sheep OA model induced by complete resection of the anterior cruciate ligament and medial meniscus. [130,417] MSCs are present in multiple niches in the knee-joint in subchondral bone, articular cartilage, meniscus, synovial fluid, synovium, and the adipose fat pad. Cartilage degeneration was also prevented and regeneration of the excised meniscus was prominent.…”

“…[416] The knee-joint menisci protect other knee-joint tissues from degenerative changes thus repair of the menisci is important for the global health and function of the knee-joint. [130,417] MSCs are present in multiple niches in the knee-joint in subchondral bone, articular cartilage, meniscus, synovial fluid, synovium, and the adipose fat pad. Developmental studies demonstrate that MSCs have chondrogenic roles during embryogenesis and diarthrodial joint development, [251] and also suggest that synovium-derived MSCs have migratory properties homing to sites of cartilage damage where they attempt to undertake cartilage repair in adulthood.…”

“…Cartilage degeneration was also prevented and regeneration of the excised meniscus was prominent . The knee‐joint menisci protect other knee‐joint tissues from degenerative changes thus repair of the menisci is important for the global health and function of the knee‐joint …”

Characterization of Synovial Cytokine Patterns in Bucket-Handle and Posterior Horn Meniscal Tears

“…Meniscal preservation has been suggested as the treatment of choice since it has been known for a long time that partial meniscectomy is strongly correlated with the development of early OA in children [ 8 ]. In addition, recent studies indicate that increased synovial fluid inflammatory cytokines, consequent to meniscal tears, may alter interactions between different articular tissues [ 9 ] and may lead to development of PTOA [ 10 – 12 ]. The cytokine pattern associated with anterior cruciate ligament (ACL) injury also suggests involvement of inflammatory cytokines in the onset and progression of PTOA [ 13 , 14 ].…”

Higher Incidence of Complete Lateral Meniscal Root Tears in Revision Compared With Primary Anterior Cruciate Ligament Reconstruction

“…T he menisci are critical stabilizing structures in the knee that become especially important in the setting of anterior cruciate ligament (ACL) deficiency. [1][2][3][4] The lateral meniscus, particularly its posterior root, is a secondary stabilizer to the pivot shift. Musahl et al 5 showeddand Frank et al 3 confirmeddthat a lateral meniscectomy further destabilized the ACL-deficient knee during a simulated pivot-shift maneuver.…”