Musculus pronator quadratus, also known as the pronator quadratus muscle, is a deep muscle located in the forearm. It is one of the muscles responsible for the rotation of the radius bone in the forearm, specifically turning the palm of the hand downward (pronation).
The muscle is located on the anterior (front) aspect of the forearm and is rectangular in shape, hence its name "quadratus." It is situated deep to the other muscles of the forearm, just above the wrist joint.
The musculus pronator quadratus originates from the anterior surface of the ulna, the larger of the two bones in the forearm, near the wrist joint. From this origin, it extends upwards and diagonally across the forearm. It then inserts onto the anterior surface of the radius, the other bone in the forearm.
When the musculus pronator quadratus contracts, it causes the radius to cross over the ulna, resulting in pronation of the forearm. This movement is involved in actions such as turning a doorknob, using a screwdriver, or playing certain musical instruments. It also acts to stabilize the distal radioulnar joint, which allows for the rotational movement of the forearm.
The pronator quadratus muscle is innervated by the anterior interosseous nerve, a branch of the median nerve. It receives its blood supply from the anterior interosseous artery.
In summary, the musculus pronator quadratus is a deep muscle in the forearm that plays a crucial role in forearm pronation and stabilization of the radioulnar joint.
