A 3D finite element model of a human knee was constructed to study the response of articular tissues to loads applied to the surface of the femur similar to normal and extreme movements of the joint as in sports activities. A solid model of the femoral and tibial cartilages and menisci were built from post mortem MR images of human knee at full extension using the Pro/Engineer software package. The knee kinematics data was registered for this model and successive articular surface positions were obtained as a function of flexion angle. The cartilage and menisci were modeled as nonlinear orthotropic materials and contact elements were used to compose the contact layer between articular surfaces. The model determined average contact areas and stress values, which were then compared with published experimental results for equivalent boundary conditions. The presence of menisci increased the contact area in the knee joint, thus creating lower contact stresses on the cartilage than those measured experimentally. Validation of results allows the utilization of 3D knee model for determining the contact areas and the contact stress field for diverse bones positions simulating sports activities.