Meniscus Repair

The menisci play a very important role in maintaining healthy articular cartilage. The knee meniscus is a functional structure, that protects the articular cartilage by both increasing the joint congruity and contact area and preventing the focal concentration of stresses. Three areas can be distinguished in the meniscus, the area in which the meniscus joins the capsule, the vascular area (red) and the avascular area (white), which are important when it comes to determining the indications and taking decisions with regard to repair. On the other hand, the meniscus is partly covered by the synovial, without forming part of it, and synovial cells could play an important role in healing, because they may differentiate producing pluripotential cells.

The menisci are also easily injured and difficult to repair. An injury to the medial or lateral cartilage is commonly found in asymptomatic individuals, and even more frequent in osteoarthritis (OA) patients. Meniscus injuries have been associated with early onset of OA, and meniscectomy is often followed by signs of OA. New vessel formation from preexisting capillaries is essential for repairing the damaged tissues and experimental studies have provided a different perspective on avascular area lesions suggesting that this part of the meniscus is unlikely to heal. The mechanisms of meniscal repair follow two patterns, the extrinsic pathway, which is usually used in lesions of the vascular area where there is a network of capillaries, which supply undifferentiated mesenchymal cells with nutrients to induce healing, and the intrinsic pathway, which is based on the self-repair capacity of the meniscal fibrocartilage and the synovial fluid. The more central the location of the meniscus injury, the lower the intrinsic responsiveness is. On the other hand, the origin of the repair cells is uncertain, but the presence of fibroblasts in the meniscal injury at an early stage suggests that the superficial meniscal cells and the synovial cells have an important role as a source of stem cells in the joint.