Extensor Carpi Ulnaris (ECU) Subluxation

Original Editor - Laura Chimimba
Top Contributors - Laura Chimimba, Vidya Acharya and Kirenga Bamurange Liliane

Introduction[edit | edit source]

Extensor Carpi Ulnaris (ECU) muscle primary functions at the wrist joint is to move the joint into extension and ulnar deviations whilst also providing a stabilising force at the ulnar side of the joint. The muscle’s function will be affected by the position of the forearm as forearm pronation and supination affect the muscle’s angle of pull.  Due to the mobility required around the wrist the muscle relies on specific stabilising structures such as the fibro-osseous groove, tendon subsheath and extensor retinaculum to maintain its position at the wrist[1].

Although the incidence of ECU subluxation is low in the general population, it can be found within sports, such as tennis, golf and rugby that require forceful or repeated wrist extension/ulnar deviation or good wrist stability for hold equipment. The overall incidence of wrist injury can be up to 8.9% of all reported sports injuries but data documenting the frequencing of ECU subluxations specifically is limited[2].

However, it has been reported that the incidence of ECU injury is 1 case/18 players/year in professional tennis players. Men were more frequently affected with 42% of all athletes within the study of 50 professional tennis players having ECU instability[3]. In contrast the prevalence of ECU injuries specifically within golf, has been poorly recognised although it is acknowledged that the wrist is frequently injured in both amateur and professional golfers[1]. Though within professional Rugby League in England, it has been found that the incidence of acute ECU injury is 1 injury/60 players/year, with a significant proportion (50%) requiring surgical repairs in this cohort[1].

Clinically Relevant Anatomy[edit | edit source]

ECU Origin:

  • Lateral epicondyle of the humerus via the common extensor tendon.
  • Posterior border of the ulna.       

ECU Insertion:

  • Medial side of the base of the fifth metacarpal.

The tendon itself, passes under the extensor retinaculum within a synovial sheath that forms the 6th compartment of the wrist, within a grove lateral to the ulna styloid process.  The function of the extensor retinaculum is predominantly to prevent bowstringing of the tendon as it passes across the wrist[5].

Nerve supply:

  • Posterior interosseous branch of the radial nerve
  • Nerve root C7/8

Muscle Action:

  • Wrist extension – along with extensor carpi radialis longus (ECRL) and brevis (ECRB)
  • Ulnar deviation of the wrist – along with flexor carpi ulnaris (FCU)


The ECU tendon can be palpated on the dorsal aspect of the wrist with the wrist in resisted extension and ulnar deviation.

Mechanism of Injury / Pathological Process
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Common risk factors for ECU injury are[1]:

  • Wrist loading with the ECU is in a vulnerable position (flexion during supination and ulnar deviation).
  • Sudden lateral force applied to the wrist during an isometric contraction of the ECU.

Acute injuries are commonly associated with some form of 'trauma' that requires high levels of wrist extensor or ulnar deviation forces to be produced, such as:

  • Hitting a powerful backhand during tennis where the forearm is reuired to create top spin by moving forcefully from pronation to supination[1].
  • Hitting a solid object during the golf swing whilst the golf club moves from a radially deviated position to neutral, and the ECU contracts isometrically to stabilize the joint[1]
  • Contact sports like rugby that require the athlete to hold the ball (and thus contract the ECU isometrically in maximal supination) to maintain possession when entering a ‘contact’.  The resultant force during the 'contact' can result in a tear of the tendon’s subsheath and a resultant sublaxation[1].

An athlete/patient may report that they felp a "snap", "pop" or a "tear" at the time of the trauma.

Chronic injuries will occur gradully over time and are potentially due to overuse or technical errors overloading the ulnar side of the wrist. Over time the ECU tendon subsheath will be damaged thus causing the subluxation. An athlete/patient may go on to develop co-comittant tenosynovitis/tendinopathy as the tendon becomes irritated by repeated rubbing against the ulna styloid during subluxations.

Clinical Presentation[edit | edit source]

Commonly athletes/patients present complaining of persistent ulnar wrist pain aggravated by activities requiring pronation and supination, which may be associated with a “clicking” or "snapping" sensation.

Objectively, a thorugh wrist assessment should be completed to aid identification of associated pathologies and to rule out any additional differential diagnoses[6].

  • Range of motion (ROM): likely full other except during the acute phase of injury and will potentially present with pain on
    • passive wrist radial deviation
    • active wrist extension and/or ulnar deviation
  • Subluxation will occur during active supination, flexion and ulnar deviation and relocate during pronation.
    • it is rare for this to occur passively due to the reduction in tendon tension when the muscle is not contracting.
    • should a dislocation occur during passive movement, the ECU can be considered as grossly unstable.
    • the presence of pain should be noted as pain severity may guide a patient towards a surgical approach.
  • Tenderness on palpation of the 6th dorsal compartment and the ECU tendon will localise the are of discomfort.
    • most athletes/patients with acute ECU subsheath ruptures or tendinopathies will be tender distal to the ulna styloid and groove, whilst those with a TFCC injury may present with tenderness localised to the wrist joint line[6]

Diagnostic Procedures[edit | edit source]

Although most ECU subluxation diagnoses can be made through a good clincal examination, diagnostic imaging may be benefical to rule out concomitant pathology or to confirm the diagnosis in subtle cases.

  • X-rays: will like be unremarkable but pronated grip views or other specialised plain radiographs may be helpful for assessing other possible differential diagnoses
  • MRI: can be a sensitive and specific modality for the assessment of the ECU but the images should include studies with the wrists positioned in pronation, supination and neutral to maximise sensitivity. Comparison with the asymptomatic wrist is also helpful to assess the relative position of the ECU within the ulnar osseus groove in all positions[6].
  • Ultrasound: is useful for assessing the dynamic stability of the ECU tendon as the tendon can be visualised whilst the patient/athlete pronates and supinates their forearm.

Outcome Measures[edit | edit source]

Management / Interventions
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Conservative Management[7]

  • Wrist splint or long arm cast – in pronation and radial deviation (4-6 weeks)
  • Appropriate conditioning programme to maintain fitness whilst wrist is immobilised
    • Aim to meet national physical activity guidelines in the amateur athlete or to maintain appropriate levels of cardiovascular fitness in the professional athlete to aid an efficient return to competition on completion of their rehab.
  • ROM recovery post immobilisation
    • AAROM/AROM exercises: consider taping ECU during this time to help maintain tendon stability
  • Progressive strengthening programme:
    • Scapular stability
    • Rotator cuff strength and endurance exercises
    • Isometric -> isotonic wrist strengthening exercises
    • Wrist stability exercises
    • Sports-specific training
      • Including review of equipment (eg tennis racket grip -> greater risk of injury with a western or semi-western style of grip due to the high amounts of top spin generated)[8]
  • Full recovery of function would be expected in 3-4 months with appropriate rehab.

Surgical Management[9]

  • ECU subsheath reconstruction +/- wrist arthroscopy
    • if nonoperative management fails
  • Technique
    • direct repair in acute cases
    • chronic cases may require an extensor retinaculum flap for ECU subsheath reconstruction
  • Wrist arthroscopy shows concurrent TFCC tears in 50% of cases
  • Post operative rehab will follow similar principles to those described for conservative management.
  • Full recovery of function would be expected in 3 months with appropriate rehab[7].

Differential Diagnosis[6][9][edit | edit source]

  • ECU Tenosynovitis
  • ECU Tendinopathy
  • Lunotriquetral ligament injury
  • TFCC tear
  • Ulnar styloid impaction syndrome
  • Ulnar styloid fracture
  • Hook of Hamate fracture
  • Pisotriquetral arthritis

References[edit | edit source]

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Campbell D, Campbell R, O’Connor P, Hawkes R. Sports-related extensor carpi ulnaris pathology: a review of functional anatomy, sports injury and management. Br J Sports Med. 2013;47(17):1105–11.
  2. Rettig AC, Ryan RO, Stone JA. Epidemiology of hand injuries in sports. In PA: WB Saunders; 1992.
  3. Montalvan B, Parier J, Brasseur JL, Le Viet D, Drape JL. Extensor Carpi Ulnaris injuries in tennis players: a study of 28 cases. Br J Sports Med. 2006;40(5):424–9; discussion 429.
  4. Campbell D, Campbell R, O’Connor P, Hawkes R. Sports-related extensor carpi ulnaris pathology: a review of functional anatomy, sports injury and management. Br J Sports Med. 2013;47(17):1105–11.
  5. Soames RW, Palastanga N. Anatomy and human movement: Structure and function. 7th ed. London, England: Elsevier Health Sciences; 2018.
  6. 6.0 6.1 6.2 6.3 Themes UFO. Surgical Treatment for Extensor Carpi Ulnaris Subluxation [Internet]. Musculoskeletalkey.com. 2016 [cited 2021 Nov 23]. Available from: https://musculoskeletalkey.com/surgical-treatment-for-extensor-carpi-ulnaris-subluxation/
  7. 7.0 7.1 Graham TJ. Pathologies of the Extensor Carpi Ulnaris (ECU) tendon and its investments in the athlete. Hand Clin. 2012;28(3):345–56, ix.
  8. Cunha J, Martins Ú, Gomes D, Matos J, Moreira J, Aguiar-Branco C. P-45 Conservative treatment of traumatic Extensor Carpi Ulnaris instability in a tennis player: case report. Br J Sports Med. 2016;50(Suppl 1):A56.2-A57.
  9. 9.0 9.1 Abbasi D. Snapping Extensor Carpi Ulnaris (ECU) [Internet]. Orthobullets.com. [cited 2021 Nov 28]. Available from: https://www.orthobullets.com/hand/6030/snapping-extensor-carpi-ulnaris-ecu