Regional Variations in Cartilage Mechanics and Composition Suggest a Sensitivity to Changes in Chronic Joint Loading Patterns

It has been suggested that variations in cartilage mechanical properties and biochemistry within a joint may be critical in understanding the implications of altered joint kinematics as a pathway to the initiation of knee osteoarthritis (OA) [1]. For example, the kinematic changes resulting from anterior cruciate ligament (ACL) injury have been suggested as a mechanism for the initiation of OA by altering chronic joint loading patterns in a tissue with low adaptation potential [1]. This mechanism would suggest that regions of cartilage subjected to different habitual post-natal mechanical loading might exhibit, among other things, differences in biochemical content and mechanical properties. The tibial plateau offers a good test bed to evaluate this mechanism since peripheral region articular cartilage (covered by the menisci) appears to experience lower contact pressures in vivo during weight-bearing activity than regions of cartilage exposed to cartilage-cartilage contact [2, 3]. Thus, the purpose of this study was to test the hypothesis that there are significant regional differences in cartilage mechanical properties (including dynamic shear modulus, phase shift angle, and equilibrium Young’s Modulus) and biochemistry (including collagen content, sulfated glycosaminoglycan (s-GAG) content, and water content) between the central and peripheral regions of the porcine tibial plateau.