Extensor Carpi Ulnaris

Introduction

Diagrammatic representation of the change of position of the extensor carpi ulnaris tendon between pronation and supination. There is an angulation of the tendon as it exits the subsheath in supination and flexion.

Alternative Names

• Extensor carpi ulnaris
• ECU

Origin

• Lateral epicondyle of humerus and posterior surface of ulna

Anatomic Course

• Passes through the fibro-osseous tunnel of the sixth dorsal compartment
• Lays within the bony groove on the dorsal ulna
• Maintained here by extensor retinaculum of the wrist

Insertion

• Base of medial side of 5th metacarpal
• Variable contribution to wrist flexion/extension depending on forearm position

Actions: Supination

• ECU tendon lies in dorsal position
• Results in greater contribution to true wrist extension
• Tendon is under greater tension in supination

Actions: Pronation

• ECU tendon lies more palmar and ulnar
• This diminishes contribution to wrist extension
• Tendon tracking studies show ECU excursion decreases by 60% in neutral/pronation

Vascular Supply

• Ulnar Artery

Innervation

• Deep branch of Radial Nerve
• Posterior Interosseous Nerve

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Clinical Significance

• Wrist Tendinopathies
• Lateral Epicondylitis
• Extensor Carpi Ulnaris Tendinopathy

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See Also

• Wrist Pain (Main)
• Hand And Wrist Anatomy
• Physical Exam Wrist

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