the parts point knee onto the ground
knee is part_of_leg. right_knee_joint is not knee_joint. left_knee_joint is knee. left_knee_joint is knee_joint. left_knee_joint is not knee_joint. right_knee_joint is knee. right_knee_joint is knee_joint. right_knee_joint is not knee. knee is not part_of_leg. left_knee_joint is not knee.