Extensor carpi radialis longus

At a glance

English

Extensor carpi radialis longus

Latin (TA2)

Extensor radialis longus carpi

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the extensor carpi radialis longus

This long radial wrist extensor counts among the superficial muscles of the back of the forearm, though its upper part forms the outer edge of the forearm beside brachioradialis. It begins higher than any other wrist extensor, above the elbow joint, so it also crosses the elbow.

Its fibres come from the lower third of the humeral lateral supracondylar ridge and from the lateral intermuscular septum. The belly is short and gives way to a long tendon about a third of the way down the forearm. This tendon runs along the lateral surface of the radius, is crossed obliquely by two thumb muscles, the long abductor and the short extensor, and passes under the extensor retinaculum in the second dorsal compartment with extensor carpi radialis brevis. It finishes on the back of the index metacarpal base, towards the thumb side.

Pulling on the index metacarpal, the muscle extends the wrist and draws the hand towards the radius. Acting together with flexor carpi radialis it gives a clean radial deviation, and with extensor carpi ulnaris it gives straight extension. Since it passes in front of the elbow axis it can also assist flexion of the elbow a little. It is supplied by the radial nerve itself, before the nerve divides, and receives blood from the radial recurrent artery and branches of the radial artery.

Its tendon is a useful donor in tendon transfer surgery and is often chosen to restore function after nerve injury. Because its branch leaves the radial nerve high, wrist extension can be partly kept when the posterior interosseous nerve alone is damaged.

Attachments, action and supply

Origin

Lower third of the humeral lateral supracondylar ridge and the lateral intermuscular septum.

Insertion

Back of the index metacarpal base, on the side nearer the thumb.

Action

Extends and abducts the hand at the wrist; weakly assists flexion of the elbow.

Nerve supply

Radial nerve, before its division (C6, C7).

Blood supply

Radial recurrent artery and branches of the radial artery.