Location and attachment
- Origin: lateral supracondylar ridge of the humerus.
- Insertion: dorsal surface of the base of the 2nd metacarpal bone.
Topographically, the muscle lies most laterally in the forearm. In a cross-section of the middle third of the forearm, it is located on the lateral side together with the brachioradialis muscle (m. brachioradialis) and the extensor carpi radialis brevis muscle (m. extensor carpi radialis brevis). For spatial orientation: anteriorly at this level are the flexor digitorum superficialis, pronator teres, flexor carpi radialis, and palmaris longus; posteriorly are the extensor digitorum and extensor carpi ulnaris; and between the bones are the flexor digitorum profundus, flexor pollicis longus, and supinator.
What is its function?
The primary function of the extensor carpi radialis longus is wrist extension. In addition, the muscle abducts the wrist, producing radial deviation.
Blood supply and innervation
- Blood supply: provided by branches of the radial artery (a. radialis) and the radial recurrent artery (a. recurrens radialis).
- Innervation: supplied by the radial nerve — n. radialis (C6–C7 segments).
Topography and adjacent structures
At the level of the elbow joint, cross-sectional structures include the extensor carpi radialis longus, brachioradialis, and anconeus muscles, the tendons of the biceps and triceps brachii, and the lateral epicondyle. Important neurovascular bundles, including the radial, median, and ulnar nerves, also pass through this region.
In the most common anatomical description, the muscle participates in the formation of the radial nerve canal. This canal is formed by three muscles crossing over the nerve: the brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis. Medial to the nerve in this zone lies the brachialis muscle (m. brachialis), and posterior to it is the lateral epicondyle of the humerus.
Clinical significance
- Wartenberg's syndrome (cheiralgia paresthetica): entrapment neuropathy of the superficial branch of the radial nerve can occur due to its compression between the tendons of the brachioradialis and extensor carpi radialis longus muscles. This is precipitated by pronation of the wrist with ulnar flexion (e.g., during prolonged computer mouse use), external compression (watch strap, handcuffs), or iatrogenic causes (chronic compression after creation of an arteriovenous fistula between the radial artery and cephalic vein for hemodialysis).
- Electromyography (EMG): the extensor carpi radialis longus is one of the target muscles during needle EMG. The study is performed to determine the severity of denervation and reinnervation changes in the muscles. The physician evaluates spontaneous activity, motor unit potential (MUP) recruitment, and MUP parameters (recommendation strength grade — C, level of evidence — 4).
Class and exam questions
What are the origin and insertion sites of the extensor carpi radialis longus?
The muscle originates from the lateral supracondylar ridge of the humerus and inserts onto the dorsal surface of the base of the 2nd metacarpal bone.
Which arteries supply this muscle?
Blood supply is provided by branches of the radial artery (a. radialis) and the radial recurrent artery (a. recurrens radialis).
In the development of which entrapment syndrome does the tendon of this muscle participate?
Its tendon is involved in the pathogenesis of Wartenberg's syndrome (cheiralgia paresthetica). The superficial branch of the radial nerve may be entrapped between the tendons of the extensor carpi radialis longus and brachioradialis.
Which muscles form the radial nerve canal in the elbow region?
In the most accepted anatomical interpretation, the canal is formed by three muscles crossing over the nerve: the brachioradialis, as well as the extensor carpi radialis longus and brevis.
What else to study on this topic
- Brachioradialis muscle (m. brachioradialis)
- Extensor carpi radialis brevis muscle (m. extensor carpi radialis brevis)
- Radial nerve (n. radialis) and its branches
- Wartenberg's syndrome (cheiralgia paresthetica)
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