The pronator teres muscle is located on the palm side of the forearm, below the elbow. Aided by the pronator quadratus, its function is to rotate the forearm palm-down, or pronation. Innervated by the median nerve, the pronator teres muscle has two heads -- the humeral head and the ulnar head. As the names imply, they connect the ends of the humerus and the ulna to the radius. The larger and shallower of the two, the humeral head, begins above the medial epicondyle, on the medial supracondylar ridge and the common flexor tendon. The ulnar head originates below the elbow on the inside of the coronoid process of the ulna. The two heads come together, cross the forearm diagonally, and insert halfway down the lateral surface of the radius via a tendon. Pronator teres syndrome is sometimes credited to neurogenic pain in the wrist and is caused by overactivity of the pronator teres muscle in which the median nerve becomes entrapped. Repetitive throwing or turning of a screwdriver can cause pronator teres syndrome.
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In Depth: Pronator teres