Supinatori

Supinatori, or supinator muscles, are two forearm muscles responsible for supination of the forearm. They lie in the posterior compartment of the forearm and form a curved muscle that wraps around the proximal radius.

The supinator consists of two parts: a superficial head and a deep head. The superficial head originates from the lateral epicondyle of the humerus and adjoining ligaments, including the radial collateral and annular ligaments. The deep head originates from the supinator crest and adjacent surface of the ulna. The fibers insert on the proximal third of the radius, spiraling around the bone so that the insertion lies on its lateral surface.

Innervation is via the deep branch of the radial nerve, known as the posterior interosseous nerve as it passes through the muscle. Blood supply is provided mainly by the radial recurrent artery and the posterior interosseous arteries. Functionally, the supinators are the primary muscles that supinate the forearm, acting in concert with the biceps brachii. Their action is especially important when the elbow is extended; when the elbow is flexed, the biceps brachii contributes more to supination.

Clinical notes include the relationship of the deep branch of the radial nerve to the muscle. The nerve traverses the supinator, and entrapment or injury in this region can lead to posterior interosseous syndrome, characterized by forearm pain and weakness in resisted supination without significant sensory loss. Injury to the supinators or their nerve supply can impair forearm rotation and grip mechanics.