MECHANICAL AND BIOCHEMICAL-CHANGES IN THE SUPERFICIAL ZONE OF ARTICULAR-CARTILAGE IN CANINE EXPERIMENTAL OSTEOARTHRITIS

The changes in the tensile mechanical properties and biochemical compo sition of the superficial zone of articular cartilage were examined in a canine model of early osteoarthritis generated by transection of th e anterior cruciate ligament. Sixteen weeks following ligament transec tion, the tensile stiffness of the articular cartilage was decreased b y 44% and the ion-induced stress relaxation of the tissue was increase d by 57% compared with the contralateral control. Biochemical analyses indicated that the water content of the experimental tissue was incre ased by 13%, which was reflected as an apparent 37% decrease in the pr oteoglycan content and a 36% decrease in the collagen content (express ed per wet weight). The hydroxypyridinium crosslink density was decrea sed in the experimental tissue by 11%. A significant negative correlat ion was found between the ion-induced stress relaxation and the hydrox ypyridinium crosslink density in both control tissue (R = -0.56) and e xperimental tissue (R = -0.70). No correlation was noted between the t ensile stiffness and the biochemical composition of the tissue. These results suggest that, in the superficial zone of articular cartilage, the structure of the tissue may play a more important role than the co mposition in the determination of its mechanical properties. A major e vent observed in the model of early osteoarthritis appears to be the d isruption and remodeling of the collagen network in the superficial zo ne of the articular cartilage.