The radius is one of the two bones in the forearm. It is a long bone and its major features include the radial head, radial tuberosity, and distal end.
Biomechanically, it is larger distally and therefore makes up the major part of the wrist. Like the ulna, the radius enables a variety of different activities requiring a range of movement. The radius is one of the two rigid members within the forearm, the second major component in the kinematic chain of the arm.
The radius is part of two major body joints, the elbow and the wrist; with the ulna, it is part of two smaller but important joints, the proximal and distal radio-ulnar joints. The radial head is an articular surface of the proximal radius. The proximal surface is convex and articulates with the capitulum of the humerus to form a limited ball-and-socket joint, the other of the two joints that make up the elbow.
The distal end of the radius contains an articular surface to mate with the carpal bones and another articular surface, the ulnar notch. Together with the distal end of the ulna, eight carpal bones, and the proximal portions of the five metacarpal bones of the palm, it forms the wrist joint.
