Extensor carpi ulnaris tendinopathy

Last revised by Bahman Rasuli on 27 Sep 2023

Extensor carpi ulnaris (ECU) tendinopathy is varied and includes tendinosis, (stenosing) tenosynovitis, tendon instability, and (rarely) rupture. 

Athletes at increased risk of ECU tendinopathy include those who participate in 1,2:

  • racquet sports, e.g. tennis
  • club sports, e.g. golf
  • high-impact contact sports, e.g. rugby

Patients typically present with ulnar-sided wrist pain and/or pain on wrist extension. Localized swelling may be present. 

A positive ECU synergy test appears sensitive although not 100% specific for ECU tendinopathy. With the elbow in 90º flexion and the forearm in full supination, resistance to thumb abduction with counter pressure on the middle finger. Reproduction of dorsal-ulnar wrist pain is considered positive for ECU tendinopathy although the test may also be positive for triangular fibrocartilage complex or lunotriquetral pathology 1.

Numerous pathologies can affect the ECU tendon 2:

  • tenosynovitis
    • causes by repetitive wrist flexion/extension, especially in supination
    • in non-athletes, consider rheumatoid arthritis
    • stenosing tenosynovitis is rare
  • tendinosis
    • results from overuse
  • tendon instability
    • ranges from subluxation to gross dislocation
      • common finding in asymptomatic individuals 4
      • on neutral wrist MRI, severe subluxation (>50%) and associated with ulnar-sided wrist pain, sprain of the dorsal radioulnar ligament, and tenosynovitis in a short/shallow ulnar groove can be considered symptomatic 5
    • results from ECU subsheath injury/dysfunction
    • usually the result of single acute trauma

Ultrasound and MRI are the mainstays of ECU tendon imaging, with ultrasound offering the advantage of dynamic assessment, Doppler interrogation for inflammation, and assessment of the contralateral ECU tendon 2

Other causes of ulnar-sided wrist pain should be considered such as 2,3:

  • ECU tendon sheath becomes more prominent distal to the ulnar styloid and should not be mistaken for tenosynovitis 2

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