Extensor carpi radialis brevis originates at the lateral epicondyle and extends plus abducts the wrist.
The extensor carpi radialis brevis is a short, thick muscle in the posterior compartment of the forearm. It lies just medial to the extensor carpi radialis longus and assists in extending and abducting the wrist. It plays a central role in stabilizing the wrist during gripping and is commonly involved in overuse injuries such as tennis elbow.
The muscle is located in the lateral posterior forearm. It originates from the lateral epicondyle of the humerus and inserts into the base of the third metacarpal bone. It lies deep to the extensor carpi radialis longus proximally and superficial to deeper extensors like the extensor digitorum.
The extensor carpi radialis brevis has a compact muscle belly that transitions into a tendon passing beneath the extensor retinaculum.
The extensor carpi radialis brevis contributes to:
Supplied by the deep branch of the radial nerve (C7–C8), which becomes the posterior interosseous nerve after piercing the supinator. The muscle receives its innervation before the nerve enters the supinator.
Proximally, it lies deep to the extensor carpi radialis longus and lateral to the extensor digitorum. At the wrist, its tendon is just medial to that of the longus. The radial nerve passes nearby, making the area clinically significant.
Although less visible than the extensor carpi radialis longus, its tendon contributes to the tendon group palpable on the dorsolateral side of the wrist during wrist extension.
Derived from the extensor muscle mass of the posterior compartment during limb bud development, the extensor carpi radialis brevis shares embryological origins with the other wrist extensors and is innervated by the radial nerve consistent with its dorsal origin.
In many non-human primates, the muscle plays a greater role in climbing and weight-bearing on the forelimbs. In humans, it has adapted for fine motor control and wrist stability during tool use and precision tasks.