THE MENISCI OF THE KNEE-JOINT - ANATOMICAL AND FUNCTIONAL-CHARACTERISTICS, AND A RATIONALE FOR CLINICAL TREATMENT

The menisci and their insertions into bone (entheses) represent a func tional unit. Thanks to their firm entheses, the menisci are able to di stribute loads and therefore reduce the stresses on the tibia, a funct ion which is regarded essential for cartilage protection and preventio n of osteoarthrosis. The tissue of the hypocellular meniscal body cons ists mainly of water and a dense elaborate type I collagen network wit h a predominantly circumferential alignment. The content of different collagens, proteoglycans and nonproteoglycan proteins shows significan t regional variations probably reflecting functional adaptation. The m eniscal horns are attached via meniscal insertional ligaments mainly t o tibial bone. At the enthesis, the fibres of the insertional ligament s attach to bone via uncalcified and calcified fibrocartilages. This a natomical configuration of gradual transition from soft to hard tissue , which is identical to other ligament entheses, is certainly essentia l for normal mechanical function and probably protects this vulnerable transition between 2 biomechanically different tissues from failure. Clinical treatment of meniscal tears needs to be based on these specia l anatomical and functional characteristics. partial meniscectomy will preserve some of the load distribution function of the meniscus only when the meniscal body enthesis entity is preserved. Repair of periphe ral longitudinal tears will heal and probably preserve the load distri bution function of the meniscus, whereas radial tears through the whol e meniscal periphery or more central and complex tears may be induced to heal, but probably do not preserve the load distribution function. There is no proof that replacement of the meniscus with an allograft c an reestablish some of the important meniscal functions, and thereby p revent or reduce the development of osteoarthrosis which is common aft er meniscectomy. After implantation, major problems are the remodellin g of the graft to inferior structural, biochemical and mechanical prop erties and its insufficient fixation to bone which fails to duplicate a normal anatomical configuration and therefore a functional meniscal enthesis.