pronador

Pronador, or pronator, is a term used in anatomy to describe a muscle or group that causes pronation of the forearm, turning the palm to face downward or anteriorly. In humans the primary forearm pronators are the pronator teres and the pronator quadratus.

The pronator teres is a two‑headed muscle that originates from the medial epicondyle of the humerus and the coronoid process of the ulna, inserting on the lateral midshaft of the radius. Its main action is forearm pronation, with a secondary role in elbow flexion. The pronator quadratus is a square, flat muscle on the distal forearm, arising from the distal anterior ulna and inserting on the distal anterior radius. It functions as a primary pronator when the elbow is extended and helps stabilize the distal radioulnar joint during rotation.

In forearm rotation, these muscles act together to rotate the radius around the ulna. The pronation produced by these muscles is opposed by the supinator and, depending on elbow position, by the biceps brachii. The relative contribution of each pronator varies with speed of rotation and the angle of the elbow, with the pronator quadratus more active in slow rotation and stabilization, and the pronator teres contributing more when the elbow is flexed.

Clinical relevance includes pronator syndrome, a form of median nerve entrapment near the elbow or forearm, which can cause forearm pain, weakness, and sensory changes. The term pronador is also used in Spanish-language anatomical terminology to refer to these muscles and their function.