radius /rā″dē·əs/ pl. radii [L, ray] , the lateral bone of the forearm lying parallel to the ulna and partially revolving around it. Its proximal end is small and forms a part of the elbow joint. The distal end is large and forms a part of the wrist joint. The radius receives the insertions of various muscles and articulates with the humerus, ulna, scaphoid, lunate, and triangular bones.
