Experimental studies have demonstrated that the moduli of articular cartilage in compression are one to two orders of magnitude smaller than in tension. However, only a few analyses of cartilage mechanics have been performed which account for this tension-compression nonlinearity (Soulhat et al., 1998; Ateshian and Soltz, 1999a,b). In order to understand the state of stress under loading conditions which simulate the physiologic environment of diarthrodial joints, and the possible implications for tissue failure and the pathomechanics of osteoarthritis, it is important to determine whether the tension-compression nonlinearity of cartilage significantly affects our current understanding of its response in contact mechanics. Most analyses of cartilage contact have employed linear isotropic or transversely isotropic models for cartilage, either within the context of elasticity theory or porous media theories. In this study, we present a finite element solution for the contact of a rigid spherical impermeable sphere against a cartilage layer supported on a rigid impermeable subchondral bone foundation, where cartilage is modeled using our recently proposed biphasic conewise linear elasticity model (Ateshian and Soltz, 1999a,b). A comparison is also provided with the more frequently used linear isotropic biphasic model, under similar conditions.

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