The supinator muscle is thin and rhomboid-shaped. It lies on the lateroposterior surface of the proximal portion of forearm. It originates from the lateral epicondyle of the humerus, the supinator crest of ulna, and the capsule of the elbow-joint. It extends obliquely downwards and laterally on the posterior side of forearm. Then it twists around the upper end of radius, stretching medially. It is inserted into the anterior and lateral surface radius.
Action
When it is contracted, the supinator muscle causes supination of the forearm (lateral rotation, in opposition to the medial/inward rotation executed by the pronator teres). It also assists in extension of the upper limb at the elbow-joint portion.
Innervation
It is innervated by the side branches of the radial nerve (C5-C6-C7).
Blood Supply
The supinator muscle receives oxygen-rich blood from the radial recurrent and interosseous recurrent artery.
