The mean bumper force at the impact point and the ligament force in the knee joint were examined, with calculations based on a compound pendulum model. Results indicate the possibility of minimizing these forces by varying the impact level. A mechanical model of the leg is described, and results of its use in tests simulating leg-bumper impacts are presented. The impact velocity, bumper level, and bumper padding were varied, and the impact sequence was documented by high-speed cinematography. The maximum knee deflection angle and the angular velocity of the leg after impact were derived. Based on the test data, the significance of bumper level and type for lower leg and knee injuries in car-pedestrian accidents is discussed. This study has shown that the bumper force has a maximum when the impact occurs near the lower leg center of gravity and a minimum near the knee level. The knee reaction forces have a minimum near the lower leg center of gravity. The knee ligament forces are highest for knee level impact. A deformable bumper structure can reduce the bumper force but not all knee reaction forces. The physical model can probably be developed into an instrument for rating bumper aggressiveness. The mathematical model used in the analysis is appended.