Forearm design as
related to hand mobility.
By virtue of this arrangement,
the hand can be rotated
through 180 deg.,
palm up to palm down,
with the elbow flexed. With
the arm fully extended,
participation of shoulder
and elbow allows the hand
to be rotated through almost
360 deg., palm up to
palm up. U, ulna; R, radius;
P, pronation; S, supination.