The kinematics of the knee joint are load-dependent; the length of the
lever arm of the extensor mechanism and the pathway of the instant center
of rotation vary with external load. This study was conducted to determine
if the maximum extensor torque-generating capacity of the knee joint is
dependent on the distance from the knee joint at which the external force
resisting extension is located. Maximum isometric extensor torques were
measured at 90 and 30 degrees of knee flexion while the distance from the
knee joint to the resisting force was varied. Our results demonstrated that
the subjects generated larger maximum extensor torques, at both 90 and 30
degrees of knee flexion, when the external resisting force was positioned
farther distal to the knee joint. This increase was as large as 50 per cent
with the knee at 30 degrees of flexion.