Arising from the common origin and from the lower part of the medial supracondylar ridge the main superficial belly is joined by the small deep head, which latter arises from the medial border of the coronoid process of the ulna just distal to the sublime tubercle. The median nerve lies between the two heads. The muscle, forming the medial border of the cubital fossa, runs distally across the front of the forearm to be inserted by a flat tendon into the most prominent part of the lateral convexity of the radius, between the lower ends of the anterior and posterior oblique lines. The attachment lies just behind the lateral profile of the radius.
Nerve supply of pronator teres:
By the first (highest) muscular branch of the median nerve (C6 and 7), usually arising just below the level of the elbow joint but occasionally above it, in which case the median nerve may be said to have a muscular branch in the arm.
Action of pronator teres:
The muscle pronates the forearm and flexes the elbow. In simple pronation, the flexing action of the muscle requires opposition by triceps. Its oblique origin from the humerus is functional; it exerts an adducting pull on the radius (and thus on the ulna) to oppose the abduction of anconeus.