Current strategies for articular cartilage repair.

Defects of articular cartilage that do not penetrate to the subchondral bone fail to heal spontaneously. Defects that penetrate to the subchondral bone elicit an intrinsic repair response that yields a fibrocartilaginous repair tissue which is a poor substitute for hyaline articular cartilage. Many arthroscopic repair strategies employed utilise this intrinsic repair response to induce the formation of a repair tissue within the defect. The goal, however, is to produce a repair tissue that has the same functional and mechanical properties of hyaline articular cartilage. To this end, autologous osteochondral transfer can provide symptomatic relief. This technique involves the excision of healthy cartilage plugs from 'non-load bearing' regions of the joint for implantation into the defect. Cell based transplantation methods currently involve the transplantation of expanded autologous chondrocytes to the defects to form a repair tissue. This technique again involves the excision of healthy cartilage from the joint for expansion. Current research is exploring the potential use of mesenchymal stem cells as a source for tissue engineering, as well as the combination of cells with biodegradable scaffolds. Although current repair strategies improve joint function, further research is required to prevent future degeneration of repair tissue.