We describe a method to simulate cartilage contact in diarthrodial joints such as the hip, knee and shoulder. The method derives time-dependent contact boundary conditions using kinematic, kinetic and geometric data that is collected experimentally and utilized to define the finite element (FE) analysis. The nonlinearity associated with contact is approximated using a penetration-based method, thus reducing the nonlinear problem to two linear ones, and greatly reducing the computational resources necessary. The method is applied to four shoulder models, allowing comparison of results that may be related to joint degeneration are compared. Keywords - Cartilage, finite element, shoulder, orthopaedic biomechanics.