Extensor carpi radialis brevis

At a glance

English

Extensor carpi radialis brevis

Latin (TA2)

Extensor radialis brevis carpi

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the extensor carpi radialis brevis

Extensor carpi radialis brevis belongs to the superficial group of the posterior forearm. It sits just behind and partly under its longer partner, extensor carpi radialis longus, on the radial side of the back of the forearm. The two muscles share a sheath and travel together towards the wrist.

The fleshy belly starts from the common extensor tendon on the front of the lateral epicondyle, with extra fibres taken from the elbow's radial collateral ligament and the fascia between neighbouring muscles. About halfway down the forearm it narrows into a flat tendon. This tendon slips under the extensor retinaculum in the second dorsal compartment, beside the longus tendon, and ends on the dorsal aspect of the third metacarpal base, close to the styloid process of that bone.

Because it inserts nearer the centre of the hand than the longus, the brevis is the more purely extending of the pair. It holds the wrist in slight extension whenever the fingers grip, which keeps the long finger flexors at a useful length. Working with the flexor carpi radialis it also tilts the hand towards the radial side. Its nerve is the deep branch of the radial nerve, given off before that branch enters the supinator, and its blood comes from the radial artery and the radial recurrent artery.

Clinically this is the muscle most linked with lateral epicondylitis, often called tennis elbow. Repeated gripping and wrist extension strain its origin, causing pain over the outer elbow that worsens when the wrist is extended against resistance. Rest, bracing and graded loading of the tendon are the usual first treatments.

Attachments, action and supply

Origin

Lateral humeral epicondyle through the common extensor tendon, the lateral ligament of the elbow, the radial collateral, and the adjacent intermuscular septa.

Insertion

Back of the third metacarpal base, near its styloid process.

Action

Extends the wrist and helps abduct the hand towards the radial side; steadies the wrist during gripping.

Nerve supply

Deep branch of the radial nerve (C7, C8).

Blood supply

Radial artery and its radial recurrent branch.