Analysis of the type of collagen present in osteoarthritic human cartilage.

Abnormal synthesis of type I collagen by fibrocartilage has been suggested as a mechanism involved in degenerative arthritis. Samples of normal and osteoarthritic adult femoral head cartilage were thus studied for histology and collagen composition. The electrophoretic analysis of the cyanogen bromide-derived peptides showed the sole presence of type II collagen in all normal and in all osteoarthritic samples, except those in which fibrocartilage was present. The sensitivity of the technique would not permit, however, the detection of a minute amount (less than 3%) of type I collagen in the samples. The results show that massive deposition of type I collagen occurs only when fibrocartilage is formed. It is suggested that this fibrocartilage is formed when the subchondral bone is damaged.