A technique has been developed to study the transmission of axial force
across the radiohumeral joint during simulated active motion of the elbow.
Variations in the line of action and in the amount of muscle load, as well
as in rotation of the forearm during flexion and extension of the elbow,
were assessed. Consistent patterns of force transmission were demonstrated
in the three specimens that were studied. The greatest force transmission
occurred between zero and 30 degrees of flexion, and it consistently
decreased with increased flexion. Force transmission was consistently
greater in magnitude when the forearm was in pronation than when it was in
supination. The varus-valgus pivot point with the elbow extended was
established to closely approximate the line of action of the brachial
muscle, which crosses near the center of the lateral portion of the
trochlea.