Upper limb

Extensor Carpi Ulnaris (humeral head)

Musculus extensor carpi ulnaris (caput humerale)

Origin

Lateral epicondyle of the humerus (common extensor origin)

Insertion

Base of the fifth metacarpal bone

Function

Extends and adducts (ulnarly deviates) the wrist

Innervation

Deep branch of the radial nerve (posterior interosseous nerve), C7–C8

Movement & chain

Works together with flexor carpi ulnaris as a synergist during ulnar deviation, and with the radial wrist extensors during pure wrist extension.

Palpation

Palpable on the ulnar side of the dorsal forearm, distally toward the ulnar styloid process, during combined extension and ulnar deviation of the wrist.

Clinical

Instability of the tendon in the sixth extensor compartment (subluxation) occurs with wrist trauma, with pain and a clicking sensation on the ulnar side of the wrist.

Segmental innervation

Radial nerve, C7–C8.

In clinical practice

The ECU tendon is a landmark in ultrasound examination of the ulnar wrist and in assessing tendon subluxation after wrist trauma.

Region in the model

Upper limb