Pronator quadratus
Musculus pronator quadratus
Also known as: PQ
A flat, square muscle joining the distal quarters of the ulna and radius. It is the prime mover of pronation and binds the two bones together.
Overview
Pronator quadratus is the deepest muscle of the anterior forearm. It runs transversely from the distal quarter of the anterior ulna to the distal quarter of the anterior radius. It initiates and drives pronation, with pronator teres joining in for fast or resisted movements. Its deep fibres also hold the radius and ulna together, resisting separation at the distal radio-ulnar joint, especially during weight-bearing on the hand. It is supplied by the terminal part of the anterior interosseous nerve.
Anatomy
- Origin
Distal quarter of the anterior surface of the ulna.
- Insertion
Distal quarter of the anterior surface of the radius.
- Action
Pronation of the forearm; stabilises the distal radio-ulnar joint.
- Innervation
Anterior interosseous nerve (median nerve).
- Nerve roots
C8–T1 (C7–C8)
- Arterial supply
Anterior interosseous artery.
- Relations
Covered by the tendons of FPL, FDP, FCR and FCU and by the radial and ulnar arteries. It lies on the interosseous membrane and the distal radius and ulna.
Function
- Pronates the forearm (prime mover)
- Holds the distal radius and ulna together
Clinical significance
Distal radius fracture surgery
In volar plating of distal radius fractures, pronator quadratus is elevated off the bone, and it may be repaired over the plate to protect the flexor tendons.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.