Muscle:Extensor Carpi Ulnaris

Extensor Carpi Ulnaris (ECU) is the ulnar wrist extensor of the dorsal forearm. Its trigger points (TrPs) produce a focused pattern of pain at the ulnar side of the dorsal wrist — a referral pattern that is clinically distinct from the more radially focused patterns of the extensor carpi radialis muscles. The ECU is the least frequently involved of the dorsal forearm wrist extensors under ordinary conditions; unlike the radial wrist extensors, it is seldom required to support a load against gravity in everyday activity. ECU TrPs are most commonly encountered following gross trauma, prolonged limb immobilisation, or as part of a global shoulder–elbow freezing pattern. It is almost never found with TrPs in the absence of at least one coexisting TrP in the neighbouring Muscle:Extensor_Digitorum.

Anatomy

• Proximal attachment: Common extensor tendon of the lateral epicondyle
• Distal attachment: Ulnar side of the base of the fifth metacarpal bone
• Fibre architecture: Fibre-length-to-muscle-length ratio 0.28 — longitudinal endplate zone running the length of the muscle belly. Designed for force at the expense of speed and range of motion.
• Innervation: Deep branch of the radial nerve (posterior interosseous nerve), spinal levels C6, C7, and C8
• Primary actions: Extension and ulnar deviation (adduction) of the hand at the wrist. Together with the extensor carpi radialis longus, produces strong pure wrist extension when both contract in concert. During wrist flexion, the ECU functions as the primary antagonist (EMG-confirmed).

The ECU stands out clearly from the surrounding forearm muscles when the patient vigorously spreads the fingers — this manoeuvre is used to identify the muscle for palpation.

Referred Pain Pattern

Essential pattern:

• Ulnar side of the dorsal wrist — focal and well-localised

This is a notably contained referral zone compared to the broader patterns of the extensor carpi radialis muscles. Spillover into the dorsal ulnar forearm may occur with highly active TrPs.

Activation and Perpetuating Factors

The ECU rarely develops TrPs from ordinary repetitive use. Typical activation contexts:

• Gross trauma: fracture of the ulna; shoulder dislocation
• Prolonged immobilisation: arm cast; post-surgical immobilisation of the shoulder or elbow
• Frozen shoulder syndrome: when most shoulder muscles and many elbow muscles develop TrPs simultaneously — can follow dislocation, prolonged cast immobilisation, or surgery on shoulder or elbow structures
• Secondary spread: as part of global extensor mass involvement after sustained heavy grip-and-rotation loading

Key TrP relationship: TrPs in the serratus posterior superior can induce satellite TrPs in the ECU.

Clinical Examination

History and Functional Assessment

Establish whether onset was associated with a specific traumatic event, immobilisation, or surgery. Spontaneous ECU TrP development without these precipitants should prompt examination of the shoulder girdle — particularly for a frozen shoulder pattern involving multiple proximal muscles.

The presenting complaint is typically a focal ache over the ulnar dorsal wrist, worsened by gripping with ulnar deviation.

Active Range of Motion

With the forearm in supination, test wrist flexion with radial deviation — this is the stretch position for the ECU. Pain or restriction at this combination indicates ECU TrP involvement.

Strength Testing

Resist the patient's attempt to hold the wrist extended in the ulnar direction. Elbow position is not critical for this test (unlike ECRL/ECRB testing, where elbow position changes which muscle is most effectively tested).

Trigger Point Examination

First locate the muscle: ask the patient to vigorously spread the fingers — the ECU stands out clearly from surrounding muscles.

TrPs found by flat palpation:

• 7–8 cm (approximately 3 inches) distal to the lateral epicondyle
• 2–3 cm (approximately 1 inch) from the sharp edge of the ulna, toward the dorsal surface of the forearm

An LTR from this location causes ulnar deviation of the hand — this is the characteristic direction that confirms ECU as the source.

Passive stretching of the ECU by flexing and radially deviating the hand at the wrist causes pain when TrPs are active. Resisting the patient's active effort to extend and adduct (ulnarly deviate) the hand also reproduces pain.

For the full TrP diagnostic criteria (taut band, spot tenderness, referred pain, patient recognition), see Concept:Trigger_Point.

Joint Play Assessment

Assess wrist joint play: distal radioulnar, radiocarpal, ulnomeniscocarpal, and intercarpal articulations. Articular dysfunction at any of these joints must be corrected alongside TrP treatment for full symptom resolution.

Differential Diagnosis

Condition	Must be present	Must be absent	Merely possible
ECU TrPs	Taut band with spot tenderness at characteristic location (7–8 cm distal to lateral epicondyle, near ulnar dorsal forearm); LTR causes ulnar hand deviation; ulnar dorsal wrist pain reproduced by TrP compression	Neurological deficit; joint line tenderness at DRUJ or TFCC	Ulnar dorsal wrist aching; pain with grip in ulnar deviation
ECU tendinopathy / tenosynovitis	Localised tenderness over the ECU tendon in the sixth extensor compartment (dorsal ulnar wrist, at the ulnar styloid); pain with resisted ulnar deviation at the tendon level	TrP in ECU belly (7–8 cm proximal) reproducing the wrist pain when compressed	Ulnar dorsal wrist pain; pain with forearm rotation
Distal radioulnar joint dysfunction	DRUJ joint line tenderness; reduced pronation/supination range; positive piano-key sign (dorsal DRUJ tenderness on passive pressure with forearm pronated)	Referred pain from a proximal ECU TrP reproducing the wrist symptoms	Ulnar wrist pain; wrist rotation restriction
TFCC injury	Ulnar wrist pain provoked by the TFCC compression test (axial load with ulnar deviation and forearm rotation); positive on MRI or arthroscopy	ECU or FCU TrP reproducing the ulnar wrist pain by compression	Ulnar wrist pain; clicking; grip weakness
C8 radiculopathy	Dermatomal sensory change in C8 distribution (ring and little finger, ulnar forearm); finger flexor reflex change	Focal TrP in ECU belly reproducing pain by compression	Ulnar forearm and hand pain; grip weakness

Treatment

Spray and Stretch

Patient seated or supine:

1. Position: wrist in flexion with radial deviation — elbow extension is not critical for ECU stretch (unlike the ECRL/ECRB)
2. Vapocoolant sweeps applied distally from the lateral epicondyle to the ulnar styloid, including the reference zone at the wrist
3. Clinician takes up slack in the muscle as it develops with each sweep

Postisometric relaxation: Examiner resists gentle wrist ulnar extension (the patient's contraction direction) while the patient inhales; on exhalation and relaxation, the hand is moved into flexion and radial deviation. Patient actively moves further in the stretch direction. Apply moist heat, then slow full active ROM × 3 cycles.

For general principles see Concept:Apropos_Treatment.

Trigger Point Injection

Patient's arm positioned with the lateral epicondyle uppermost:

• Locate the TrP (7–8 cm distal to lateral epicondyle, near the ulnar border of the dorsal forearm)
• Place one finger between the sharp edge of the ulna and the nodule in the muscle; place the other finger on the opposite side of the nodule to stabilise it for injection
• LTRs and characteristic referred pain patterns confirm correct needle placement

After injection: spray and stretch → hot pack → slow active ROM × 3.

For general injection principles see Concept:Trigger_Point_Injection.

Patient Education

• The ECU is not typically overloaded by ordinary gripping — if TrPs are present without clear trauma or immobilisation history, examine the shoulder girdle for the primary driver
• Avoid repetitive wrist ulnar deviation under load during recovery
• If onset followed a frozen shoulder pattern, address the shoulder girdle muscles first (see Muscle:Subscapularis, Muscle:Infraspinatus, Muscle:Teres_Major)

Satellite Trigger Points

• Muscle:Extensor_Digitorum — essentially never absent when ECU TrPs are present; examine simultaneously and treat together

Key TrP source (muscles that drive ECU as a satellite):

• Muscle:Serratus_Posterior_Superior — key TrP source for ECU satellite TrPs

Related Pages

• Muscle:Extensor_Carpi_Radialis — radial wrist extensors; examine and treat together
• Muscle:Brachioradialis — part of the extensor mass functional unit
• Muscle:Extensor_Digitorum — almost always co-involved
• Muscle:Serratus_Posterior_Superior — key TrP source for ECU satellite involvement
• Concept:Trigger_Point — diagnostic criteria, taut band, LTR, contraction knot
• Concept:Apropos_Treatment — general principles of TrP treatment
• Concept:Trigger_Point_Injection — injection principles and post-injection protocol

References

• Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1: The Upper Half of Body. 2nd ed. Baltimore: Williams & Wilkins; 1999. Chapter 34.