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:
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
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.
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.
Dorsal base of the third metacarpal
Deep branch of the radial nerve
Flexor carpi ulnaris
Extension and abduction at the wrist joint