Extensor Carpi Radialis Longus – Anatomy, Nerve Supply

Last updated: February 8, 2026Reviewed date: February 8, 2026Reading time: 4 min read
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The Extensor Carpi Radialis Longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone (metacarpal of the index finger). The extensor carpi radialis longus is an extensor...

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Article Summary

The Extensor Carpi Radialis Longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone (metacarpal of the index finger). The extensor carpi radialis longus is an extensor muscle occupying the posterior compartment of the forearm. Based on their location, all muscles off the forearm can be classified into layers (superficial...

Key Takeaways

  • This article explains Structure of Extensor Carpi Radialis Longus in simple medical language.
  • This article explains Nerve Supply of Extensor Carpi Radialis Longus in simple medical language.
  • This article explains Function of Extensor Carpi Radialis Longus in simple medical language.
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The Extensor Carpi Radialis Longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone (metacarpal of the index finger).

The extensor carpi radialis longus is an extensor muscle occupying the posterior compartment of the forearm. Based on their location, all muscles off the forearm can be classified into layers (superficial to deep) and groups (radial and ulnar). Extensor carpi radialis is classified into the following:

  • Superficial layer – together with brachioradialis, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi and extensor carpi ulnaris.
  • Radial group – together with brachioradialis and extensor carpi radialis brevis.

This muscle extends between the humerus and the second metacarpal bone. It acts on the wrist joint causing extension and abduction (radial deviation) of the hand while powered by the radial nerve. These two actions are vital for effective hand gripping.

Structure of Extensor Carpi Radialis Longus

It originates from the lateral supracondylar ridge of the humerus, from the lateral intermuscular septum, and by a few fibers from the lateral epicondyle of the humerus.[rx]

The fibers end at the upper third of the forearm in a flat tendon, which runs along the lateral border of the radius, beneath the abductor pollicis longus and extensor pollicis brevis; it then passes beneath the dorsal carpal ligament, where it lies in a groove on the back of the radius common to it and the extensor carpi radialis brevis, immediately behind the styloid process.

One of the three muscles of the radial forearm group, it initially lies beside the brachioradialis but becomes mostly tendon early on. Passing between the brachioradialis and the extensor carpi radialis brevis, this tendon continues into the second tendon compartment together with the latter muscle.[rx] It is inserted into the dorsal surface of the base of \the second metacarpal bone, on its radial side.[rx]

Extensor Carpi Radialis Longus

  • Origin: lateral supracondylar ridge of humerus
  • Insertion: base of 2nd metacarpal
  • Action: extension and abduction of the wrist
  • Innervation: radial nerve

Nerve Supply of Extensor Carpi Radialis Longus

The extensor carpi radialis longus is a wrist extensor that is innervated by the radial nerve,[rx] from spinal roots C6 and C7.[rx] All other major extensor muscles in the superficial layer of the posterior compartment (the extensor digitorum, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digiti minimi) are innervated by the posterior interosseous branch of the radial nerve.

Function of Extensor Carpi Radialis Longus

As the name suggests, this muscle is an extensor at the wrist joint and travels along the radial side of the arm, so will also abduct (radial abduction) the hand at the wrist.[rx] That is, it manipulates the wrist so as to move the hand towards the thumb (i.e. abduction—away from the mid-position of the hand) and away from the palmar side (i.e. extension—increased angle between the palm and the front of the forearm).

or

Extensor carpi radialis longus primarily acts on the wrist joint to produce two major actions:

  • Wrist extension by working synergistically with extensor carpi radialis brevis and extensor carpi ulnaris.
  • Hand abduction (radial deviation), with the help of flexor carpi radialis.

Since extensor carpi radialis longus also spans the elbow, the muscle has a minimal contribution to elbow flexion. Together with other forearm extensors, extensor carpi radialis longus plays an important role in hand gripping. In order to achieve an effective grip, the wrist must be maintained in an extended position by the forearm extensors, including the extensor carpi radialis longus. Thereby, wrist flexion is prevented and the contraction force produced by the forearm flexors is transferred to the fingers. If the wrist would not be extended, the forearm flexor tendons would be incapable to shorten sufficiently to produce a functional hand grip.

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