Cartilage injury and repair.

Articular cartilage is a complex structure that, once damaged, has little capacity for permanent repair. The problem lies in the inability of the body to regenerate tissue with the appropriate macromolecular constituents and architecture of normal hyaline cartilage. Although full-thickness defects are capable of stimulating a repair response, the resulting fibrocartilage is inferior and cannot withstand long-term, repetitive use. Numerous surgical approaches that involve penetration of subchondral bone offer short-term to moderate-term relief of symptoms, whereas other approaches have seen significant improvement through transplantation of osteochondral and periosteal tissue and implantation of autologous chondrocytes. Despite these procedures, articular cartilage damage continues to be an unmet clinical problem. Improvements in biochemical and molecular biologic techniques may allow advances in the understanding of chondrocyte and cartilage biology and may provide innovative and novel approaches to stimulating the repair of articular cartilage through biologic means.