The forearm (antebrachium) is the part of the upper limb that extends between the elbow and the wrist joints. It consists of two bones that are known as the radius and the ulna. The radius is shorter and smaller than the ulna and is found on the lateral side, while the ulna is positioned on the medial side of the forearm.

Both bones are indirectly connected by an interosseous membrane via their interosseous borders. They also directly articulate with each other at two sites, forming the proximal and distal radioulnar joints.

The proximal radioulnar joint is formed between the head of the radius and the radial notch of the ulna. The distal radioulnar joint is formed between the head of the ulna and the ulnar notch of the radius. The mentioned joints and the humeroradial joint allow the pronation and supination of the forearm, as the radius can pivot around the ulna.

Both bones also articulate with the humerus proximally, forming the elbow joint, and the carpal bones distally, forming the wrist joint. The ulna and radius also serve as attachment sites for many muscles that are responsible for extension and flexion of the forearm, wrist, and fingers.

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Bones of forearm