A two dimensional dynamic model of the human knee joint is improved by employing more realistic bone profiles and ligament models. The knee model consists of a fixed rigid femur and a moving rigid tibia connected by the fiber tissues. The two articulating surfaces are represented by polynomial equations. The knee joint ligaments are modeled as nonlinear springs with a linear-parabolic operating region which is considered to be a more representative model. The nonlinear differential equations of motion constrained by geometrical nonlinear algebraic equations are solved numerically to simulate the knee dynamics under external pulse forcing. The flexion and extension motions, and the effects of pulse direction and ligaments insertion coordinates on the ligaments tension and point contact forces are discussed.