The extensor carpi radialis brevis is one of the muscles of the superficial layer of the posterior compartment of the forearm. The term "brevis" means "short" in Latin; it has a "long" counterpart muscle, the extensor carpi radialis longus which it lies deep and medial to along much of its course.

The posterior compartment of the forearm consists of a superficial layer (7 muscles) and a deep layer (5 muscles).

The muscles of the superficial layer include:

The muscles of the superficial layer share a common origin from the lateral epicondyle and lateral supracondylar ridge of the humerus.

All the muscles of the posterior compartment are innervated by the radial nerve.

Origin

Lateral epicondyle of the humerus

The tendon of the extensor carpi radialis brevis passes underneath the abductor pollicis longus and extensor pollicis brevis, and then beneath the extensor retinaculum to insert on to the dorsal surface of the base of the third metacarpal.

Insertion

Dorsal base of the third metacarpal

Innervation

Deep branch of the radial nerve

Blood Supply

Radial artery

Antagonist

Flexor carpi ulnaris

Action

Extension and abduction at the wrist joint