pronatori

Pronatori, or pronators, are the muscles primarily responsible for forearm pronation, the movement that rotates the palm downward or backward. In human anatomy the two main pronators are the pronator teres and the pronator quadratus. A smaller contribution to pronation can come from other forearm muscles depending on the position of the arm, but the teres and quadratus are considered the primary pronators.

The pronator teres is a two-headed muscle located in the anterior compartment of the forearm. It originates from the medial epicondyle of the humerus and the coronoid process of the ulna, and inserts onto the lateral surface of the radius. The pronator quadratus lies in the distal forearm as a square-shaped muscle, attaching from the distal anterior ulna to the distal anterior radius. The quadratus acts as a deep stabilizer during pronation.

Innervation and blood supply vary between the two muscles. The pronator teres receives innervation from the median nerve (typically C6–C7). The pronator quadratus is innervated by the anterior interosseous nerve, a branch of the median nerve. Blood supply is provided by branches of the ulnar and radial arteries for the teres, while the pronator quadratus is supplied mainly by the anterior interosseous artery.

Functionally, these muscles produce forearm pronation and help stabilize the distal radioulnar joint. They act as antagonists to the supinator and related extensor muscles. Clinically, pronator syndrome refers to median nerve compression at the forearm, and injuries or overuse can impair pronation strength.