Biomechanical Properties of the Canine Knee Articular Cartilage as Related to Matrix Proteoglycans and Collagen

Abstract

The instant, creep and equilibrium responses of canine knee articular cartilages were determined after a constant load application with an in situ indentation creep test and related to the chemical composition of the tissue. Instantly, the cartilage stiffness correlated inversely with the proportion of proteoglycans (PGs) extractable with guanidium chloride. The tibial cartilage, rich in PGs but relatively poor in collagen, showed a low resistance to instant rearrangement of the solid matrix after load application. However, the resistance of the tibial cartilage to water flow during creep deformation was similar or even higher than in the femur. The rate of creep correlated inversely with the PG content. The equilibrium modulus of the femoral cartilage (0.40 MPa), 29 per cent higher than in the tibia (0.31 MPa), was related to the content of PGs, while in the tibia the direct correlation between PGs and modulus was not observed. Our results suggest that while PGs control the fluid flow in articular cartilage, a high PG content alone does not guarantee high stiffness of the cartilage. Instead, the properties of the collagen network are suggested to control particularly the instant shape alterations of the articular cartilage under compression.