A 3D pedestrian knee joint model was developed as a first step in a new description of the whole pedestrian body for computer simulations. The model was made to achieve better correlation with the results from previous tests with biological material. The model of the knee joint includes the articular surfaces, ligaments and capsule represented by the ellipsoid and plane elements as well as the spring-damping elements, respectively. The mechanical properties of the knee joint were based on available biomechanical data.To verify the new developed model with results from tests with biological material previously performed at the Department of Injury Prevention, Chalmers University of Technology, the computer simulations were carried out with the model of the knee joint using the MADYMO 3D program. To simulate different test conditions, which correspond to previous tests with biomechanical system, the following parameters were varied in our simulations: bumper height and bumper compliance. Four computer simulations were performed and compared with four test series with biological material with five tests in each series. The impact force, the condyle interface forces, the ligament forces and the ligament relative elongations were calculated and verified with the results of the tests with biological material. The output parameters calculated from the knee joint model correspond in general to what was observed in the studies with biological material.Complementary two computer simulations were performed to study the influence of the upper body mass to the distribution of the forces in the simulated knee structures. These simulations appear that body mass has an influence on the impact and condyle forces, the ligament strain and on the trajectory of the lower extremities.