kyynärluulihas

The kyynärluulihas, also known in English as the pronator quadratus, is a small, flat muscle located in the forearm. It is one of the intrinsic muscles of the forearm and is situated deep within the anterior compartment, close to the wrist joint. Its primary function is to assist in pronation of the forearm, which is the movement of turning the palm downwards.

The muscle originates from the distal (lower) quarter of the anterior surface of the ulna, which is one of the two bones in the forearm. It then extends across the wrist and inserts onto the distal quarter of the anterior surface of the radius, the other forearm bone. This anatomical arrangement allows the kyynärluulihas to pull the radius medially (towards the ulna), causing the radius to rotate over the ulna and pronate the forearm.

While the brachioradialis and pronator teres muscles are also involved in pronation, the kyynärluulihas plays a crucial role in providing a strong and stable pronation action, particularly when the forearm is already partially pronated. It also contributes to stabilizing the distal radioulnar joint, which is where the ends of the radius and ulna meet near the wrist. The muscle is innervated by the anterior interosseous nerve, a branch of the median nerve.