A four-bar knee joint measurement walking system for prosthesis design

BACKGROUND: Gait analysis is important for the lower limb prosthesis design. Simulating the natural motion of the human knee in different terrains is useful for the design and performance assessment of the prosthetic knee. OBJECTIVE: This study aimed to propose a four-bar knee joint measurement system which can simulate the natural knee motions to collect the kinetic parameters precisely and analyze the walking characteristics under different terrain conditions. METHODS: A low-cost four-bar knee joint mechanism was proposed and gait characteristics were assessed on level ground, ascending and descending stairs, and ascending and descending ramp. RESULTS: The initial knee flexion angle during stair ascent at heel strike is obviously larger than in other walking scenes. The stance phase accounts for 53% of a single gait cycle during stair descent, which is slightly lower than other walking scenarios. The period that both the hindfoot and forefoot contact the ground in ramp descent accounts for 18%, which is less than for the others. While the forefoot contacts the ground in ramp ascent, the maximum vertical ground reaction force of the forefoot occurs when the hindfoot and forefoot simultaneously contact the ground, whereas in other scenarios the forefoot contacts the ground solely. CONCLUSIONS: The four-bar knee joint can simulate the natural motion of the human knee accurately. The gait characteristics analysis of different walking scenarios indicated that the low-cost four-bar knee joint exoskeleton was suitable for human knee joint simulation.