The bones of the forearm are the ulna and radius. Both are long bones that articulate with each other at their proximal and distal ends.

The Ulna 

The ulna, located on the medial side of the forearm, is the longer of the two bones. Its proximal end, which forms most of the elbow joint, is thick and strong. It has two processes and two notches. Between its olecranon and coronoid processes lies the trochlear notch (semilunar notch), which accommodates the trochlea of the humerus. The radial notch, on the lateral side of the coronoid process, permits articulation with the radius. The distal end is much smaller than the proximal end, bearing a head and a styloid process. Laterally, the head articulates with the ulnar notch of the radius distally with the articular disk separating it from the wrist joint.

The Radius 

The radius is located on the lateral side of the forearm parallel to the ulna. The proximal end is small and has a head, neck, and tuberosity. The shallow cup, or fovea, on the proximal surface of the head articulates with the capitulum of the humerus. On the broad medial surface, the head articulates with the radial notch of the ulna. Below the neck on the medial side is the radial tuberosity (or tubercle). The distal end is large and club-shaped and forms the largest part of the wrist joint. It has two articular surfaces, one broad area that articulates with two carpal bones (the navicular and lunate) and a smaller surface on the medial side, the ulnar notch, that articulates with the ulna. Distally, the lateral surface extends into the styloid process. Colles fracture occurs at the distal radius with posterior displacement of the distal fragments, a “silver fork deformity.”

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