To the posterior of the two ridges the lower part of the interosseous membrane is attached, while the triangular surface between the ridges gives insertion to part of the pronator quadratus muscle.
12.
Thus when the arm is in a supine ( palm up ) position, contraction of pronator quadratus acts to roll the outside of the radius toward the ulna, which is pronation.
13.
As might be expected, the symptoms involve weakness in the muscle innervated by the AIN including the flexor digitorum profundus muscle to the index ( and sometimes the middle ) finger, the flexor pollicis longus muscle to the thumb and the pronator quadratus of the distal forearm.
14.
The "'pronator teres "'is a muscle of the human body ( located mainly in the forearm ) that, along with the Pronator quadratus, serves to pronate the forearm ( turning it so that the palm faces posteriorly when from the anatomical position ).
15.
It accompanies the anterior interosseous artery along the anterior of the interosseous membrane of the forearm, in the interval between the flexor pollicis longus and flexor digitorum profundus, supplying the whole of the former and ( most commonly ) the radial half of the latter, and ending below in the pronator quadratus and wrist joint.
