Extensor Digitorum

Joe Muscolino

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The extensor digitorum is seen. The extensor digitorum has been ghosted in.

The Extensor Digitorum is in the Superficial Layer of the Posterior Compartment of the forearm.



  • Lateral epicondyle of the humerus via the common extensor belly/tendon to fingers #2-5 (index, middle, ring, little).
    • The distal attachments are onto the posterior surfaces of the middle and distal phalanges of fingers #2-5 via the dorsal digital expansion.



  • Extends fingers #2-5 at the metacarpophalangeal and proximal and distal interphalangeal joints.
  • Extends the hand at the wrist joint.



  1. The extensor digitorum distal tendons spread out to create a fibrous aponeurosis called the dorsal digital expansion.
  2. The extensor carpi ulnaris is often involved with lateral elbow tendinopathy (aka tennis elbow).
  3. Some textbooks refer to the extensor digitorum as the extensor digitorum communis.