Upper limb

Pronator Quadratus

Musculus pronator quadratus

Origin

Distal anterior surface of the ulna

Insertion

Distal anterior surface of the radius

Function

The primary pronator of the forearm, most active during fast or resisted pronation

Innervation

Anterior interosseous nerve (branch of the median nerve, C8–T1)

Movement & chain

Initiates pronation and works together with pronator teres, which assists mainly during forceful pronation against resistance.

Palpation

Deeply located, just proximal to the wrist on the anterior side between the radius and ulna; not well distinguished directly due to the overlying tendon mass.

Clinical

Can be involved in pronator quadratus syndrome from an anterior interosseous nerve lesion, with weakness of pronation and of flexor pollicis longus/flexor digitorum profundus (index).

Segmental innervation

Median nerve (anterior interosseous nerve), C8–T1.

In clinical practice

Function test: pronating the forearm with the elbow fully flexed (to disable pronator teres) specifically assesses pronator quadratus and the anterior interosseous nerve.

Region in the model

Upper limb