A u-p finite element analysis of the effect of joint curvature and tissue thickness on the indentation of articular cartilage

The highly hydrated, viscoelastic nature of articular cartilage enables it to aid in lubrication and load distribution in diarthrodial joints. The u-p finite element method models the tissue as consisting of two phases-a solid phase of collagen fibrils and proteoglycan aggregates and a fluid phase of interstitial water. The method, using solid displacements (u) and fluid pressures(p) as the nodal parameters, is a valuable tool to investigate tissue behavior under different loading and geometric configurations. The present study analyzed the mechanical response of cartilage under small strain conditions when the tissue was subjected to indentation loading. Because many analytical treatments of the indentation configuration assume the cartilage-bone layer to be an infinite plane, the authors assessed the effects of curvature of joint surfaces on the mechanical behavior of cartilage. Additionally, the effect of the thickness of the tissue on its behavior was investigated.