Pathology of the meniscus.

The pathologic description of the menisci is facilitated by grouping the various disorders into etiologic groups. These include congenital anomalies, traumatic conditions, inflammatory disorders, metabolic disorders, degenerative conditions, and neoplasms. In clinical practice, traumatic conditions, as exemplified by meniscal tears of the vertical-longitudinal or vertical-transverse type, are the most important pathologic disorders. Healing of meniscal tears occurs only when the tear involves the peripheral vascularized attachment of either the lateral or medial meniscus. Intensive clinical and animal experimentation suggests that serum-derived growth factors are necessary for meniscal healing. Chondrocalcinosis is extremely frequent in the menisci of older individuals and may or may not be associated with degenerative changes of the menisci, including fibrillation, loss of protein polysaccharide ground substance, and chondrocytic proliferation. The role of degenerative changes of the menisci, including tears of the horizontal type, in the development of osteoarthritis (OA) of the knee is a subject of intense interest, as is the relationship between chondrocalcinosis and OA. Neoplastic involvement of the menisci is essentially limited to invasion by tumors starting in or, more commonly, adjacent to the knee joints.