Extensor Carpi Radialis Brevis Muscle – Functions, Anatomy

The Extensor Carpi Radialis Brevis Muscle is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.

Extensor carpi radialis brevis is a fusiform muscle found in the lateral part of the posterior forearm. Together with anconeus, brachioradialis, extensor carpi radialis longus, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris, it belongs to the superficial forearm extensor group. Crossing the elbow and wrist joints from their posterior aspects, these muscles produce extension at one or both of these joints. The specific action of extensor carpi radialis brevis is to extend and abduct the hand at the wrist joint.

Origin and Insertion of Extensor Carpi Radialis Brevis Muscle

It arises from the lateral epicondyle of the humerus, by the common extensor tendon; from the radial collateral ligament of the elbow-joint; from a strong aponeurosis which covers its surface; and from the intermuscular septa between it and the adjacent muscles.^[rx]

The fibers end approximately at the middle of the forearm in the form of a flat tendon, which is closely connected with that of the extensor carpi radialis longus, and accompanies it to the wrist; it passes beneath the abductor pollicis longus and extensor pollicis brevis, beneath the extensor retinaculum, and inserts into the lateral dorsal surface of the base of the third metacarpal bone, with a few fibers inserting into the medial dorsal surface of the second metacarpal bone.^[rx]

Anatomy of Extensor Carpi Radialis Brevis Muscle

Extensor carpi radialis brevis

• Origin: lateral epicondyle of humerus
• Insertion: base of 3rd metacarpal
• Action: extension and abduction of the wrist
• Innervation: radial nerve

Nerve Supply of Extensor Carpi Radialis Brevis Muscle

• Like all the muscles in the posterior forearm, ECR Brevis is supplied by a branch of the radial nerve.
• Extensor carpi radialis brevis is innervated directly by the radial nerve (C5- C8), or sometimes from its deep branch/posterior interosseous nerve. The radial nerve stems from the posterior cord of the brachial plexus.

Function of Extensor Carpi Radialis Brevis Muscle

• It is an extensor, and an abductor of the hand at the wrist joint. That is, it serves to manipulate the wrist so that the hand moves away from the palm and towards the thumb. The muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension. A wrist roller can be used and reverse wrist curls with dumbbells can be performed.
• When the extensor carpi radialis brevis muscle contracts together with extensor carpi radialis longus and flexor carpi radialis, it contributes to producing hand abduction (radial deviation).