Extensor carpi ulnaris muscle

Last revised by Daniel J Bell on 17 Jan 2021

Extensor carpi ulnaris (ECU) muscle is a muscle of the superficial layer of the posterior compartment of the forearm. It is separated from the extensor digitorum and the extensor digiti minimi muscles by a distinct intermuscular septum. It is the only forearm extensor that lies in its own fibro-osseous tunnel at the level of the wrist with its own subsheath as it passes through the 6th extensor compartment of the wrist. At the level of the ulna, it is covered by a subsheath, extensor retinaculum and the linea jugata. It is one of the extrinsic muscles of the hand.


Related pathology

  • tendinosis and/or tenosynovitis
    • ECU is the second most common site of upper limb tenosynovitis 3
  • subluxation of the ECU tendon with subsheath injury 3

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Cases and figures

  • Figure 1: extensor compartments of the wrist
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  • Case 1: ECU tendinopathy
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  • Figure 2: ECU subluxation (red arrow)
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  • Case 2: ECU tendinosis and tenosynovitis
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  • Case 3: subluxation - traumatic
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