The lower extremity of the ulna or distal extremity is the end of the ulna (one of two long bones in the forearm) closest to the wrist. The extremity is small, and presents two eminences; the lateral and larger is a rounded, articular eminence, termed the head of the ulna; the medial, narrower and more projecting, is a non-articular eminence, the styloid process.
The head presents an articular surface, part of which, of an oval or semilunar form, is directed downward, and articulates with the upper surface of the triangular articular disk which separates it from the wrist-joint; the remaining portion, directed lateralward, is narrow, convex, and received into the ulnar notch of the radius.
The styloid process projects from the medial and back part of the bone; it descends a little lower than the head, and its rounded end affords attachment to the ulnar collateral ligament of the wrist-joint.
The head is separated from the styloid process by a depression for the attachment of the apex of the triangular articular disk, and behind, by a shallow groove for the tendon of the extensor carpi ulnaris.