Solution of contact problems such as the three-body femur-meniscus-tibia unit in the knee are an essential part of research in diarthrodial joint mechanics. There are numerous studies which focus on geometry [1], load transfer during articulation [2] and material properties of the components of the knee joint [3], for example. Results from experimental investigations of this problem are limited, however, as there are few variables that can be measured directly. To gain a greater understanding of contact in joints, we turn to the finite element method to construct numerical solutions for this complex problem. Our finite element formulation is developed from the differential equations and boundary conditions, including the constraints of contact, that govern biphasic tissues in a joint. Even when the governing equations are linear, the problem becomes nonlinear because the contact surface is not known in advance. Our contact formulation [4] begins with the existing biphasic mixed-penalty element, and develops the appropriate contact constraints and contact detection algorithms. We can employ our computational model to do parametric analysis of the effects of geometry, loading and material properties on the deformation, fluid flow, stress and pressure throughout the soft tissues of a joint. For this study, we investigate a simplified femur-meniscus-tibia unit developed from an axisymmetric representation of the knee (see Fig. 1).
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