The pronator teres is innervated by the median nerve. The physician may notice an enlarged pronator teres muscle. The lateral corticospinal tract is responsible for the motor pathway of the pronator quadratus. In the forearm, this action is performed by pronator quadratus and pronator teres muscle. The pronator quadratus and the pronator teres are either reduced or absent. Injection of corticosteroids into the pronator teres muscle may produce relief of symptoms. About its center is a rough ridge, for the insertion of the pronator teres muscle. It then gives off the anterior interosseus branch in the pronator teres. Tinel's sign the area around the pronator teres heads should be positive. It is assisted in this action by pronator quadratus. Then the Pronator quadratus muscle is found and detached from the radius. Pronator drift indicates abnormal function of the corticospinal tract in the contralateral hemisphere. Pronator teres pronates the forearm, turning the hand posteriorly. A supinator turns the palm of the hand up; a pronator turns the palm down. Pronator quadratus&colon; originates on surfaces of the radius and ulna.