The influence of mechanical properties of subchondral plate, femoral head and neck on dynamic stress distribution of the articular cartilage.

A few finite element models have addressed the dynamic juxtaarticular stress transmission but none focused the investigation on the combined influence of the individual moduli of the underlying bones, including the subchondral plate, the femoral head and the femoral neck of the proximal femur. A finite element model including the acetabulum and the proximal femur was analyzed with dynamic loadings to study the effects of mechanical property changes in the underlying bones of the proximal femur on the stress distribution in the cartilage at the hip joint. We found the stress distribution was most sensitive to the subchondral plate stiffening, while the overall stiffening of the underlying bones had mild effect on the shear stress on the cartilage surface (or at the subchondral bone/cartilage interface) and on the strain energy density in the cartilage. Our results indicate that the subchondral plate plays a predominant mechanical role in the initial degeneration of the cartilage. The results may offer a mechanical explanation as to why the cartilage failure is common in patients with osteoarthritis but rare in patients with osteoporosis.