Pronator quadratus

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Pronator quadratus
Front of the left forearm. Deep muscles. (Pronator quadratus visible at bottom-center right.)
Latin musculus pronator quadratus
Gray's subject #125 449
Origin medial, anterior surface of the ulna
Insertion    lateral, anterior surface of the radius
Artery: anterior interosseous artery
Nerve: median nerve (anterior interosseous nerve)
Action: pronates the forearm
Antagonist: Supinator muscle

Pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.

As it is on the anterior side of the arm, it is innervated by a branch of the median nerve, the anterior interosseous nerve. Arterial blood comes via the interosseous artery.

Origin and insertion

Its fibres run perpendicular to the direction of the arm, running from the most distal quarter of the anterior ulna to the distal quarter of the anterior radius.


When pronator quadratus contracts, it pulls the lateral side of the radius towards the ulna, thus pronating the hand. It also helps to keep the two bones in the forearm bound together.

Additional images

External links

ca:Múscul pronador quadrat de:Musculus pronator quadratus hu:Négyszögű csavaró izom sv:Pronator quadratus