Proteoglycans of articular cartilage: changes in aging and in joint disease.

In human osteoarthritis and animal models of degenerative joint disease, damage to the structure of cartilage proteoglycan is a central event. Loss of proteoglycan from the matrix alters the physicochemical properties of the tissue, but the pathological process and biochemical mechanisms that lead to this loss are poorly understood. This review examines the present state of knowledge regarding proteoglycan structure and the changes that occur in aging and osteoarthritis. It also discusses how these studies will influence the development of new methods for measuring cartilage breakdown.