The proximal end of the radius illustrates the relationship of form and function. The cup-like surface of the radial head articulates with the rounded shape of the capitulum.
This forms a joint that allows for .

The rotational motion of the forearm

Explanation:

The two large bones of the forearm, one being the Ulna and the other is radial bone or radius.The Radius is larger in size than the Ulna.Radius is prism shaped, little curved longitudinally long bone.The part of two joints known as elbow and wrist comprised the Radius.Radius link with the capitulum of the humerus at the elbow region.Radius forms a joint at the wrist region with the ulna bone.