How is a subluxation extensor carpi ulnaris (ECU) etiology of ulnar-sided wrist pain diagnosed and treated?

Updated: Apr 26, 2021
  • Author: David M Lichtman, MD; Chief Editor: Harris Gellman, MD  more...
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See Differential Diagnosis for a list of conditions that cause ulnar wrist pain. Common conditions from this list are discussed below.

Subluxation of extensor carpi ulnaris

The extensor carpi ulnaris (ECU) courses through the sixth dorsal compartment, where it is held tightly to the ulnar groove by a subsheath, which is separate from the extensor retinaculum. When the ECU tendon subluxes, the subsheath is torn, whereas the retinaculum usually remains intact. [12] The mechanism that causes ECU subluxation is often forced supination, palmar flexion, and ulnar deviation. The ECU tendon is relocated with pronation.

The patient has pain over the dorsal wrist and clicking or snapping with pronation and supination. On evaluation, the subluxation can be reproduced with active forearm supination and ulnar deviation. Tenderness and swelling are often present over the ECU tendon at the ulnar head. Routine radiographic findings are negative. Further studies are often unnecessary. Magnetic resonance imaging (MRI) can show inflammation about the sheath, as well as malpositioning of the tendon.

In acute subluxation, immobilization for 6 weeks in a long-arm cast with the forearm pronated and the wrist in slight radial deviation and dorsiflexion should be attempted. With chronic and symptomatic subluxation, surgical reconstruction of the subsheath is beneficial.

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