Author: Dr Peter de Souza
Last modified: 3 March 2021

The extensor carpi ulnaris is one of the muscles of the superficial layer of the posterior compartment of the forearm. It lies medial to the extensor digiti minimi.

The posterior compartment of the forearm consists of a superficial layer (7 muscles) and a deep layer (5 muscles).

The muscles in the superficial layer include:

The muscles of the superficial layer share a common origin from the lateral epicondyle and lateral supracondylar ridge of the humerus.

All the muscles of the posterior compartment are innervated by the radial nerve.


  • Lateral epicondyle of the humerus
  • Posterior border of ulna


  • Tubercle on medial base of little finger metacarpal (V)

The tendon passes beneath the extensor retinaculum within a groove between the head and styloid process of the ulna.


  • Extension and adduction at the wrist joint


Posterior interosseus nerve (continuation of the deep branch of the radial nerve)

Blood Supply

  • Posterior interosseus artery (from common interosseus artery)
  • Radial recurrent artery


Flexor carpi radialis