Extensor carpi ulnaris
Musculus extensor carpi ulnaris
Also known as: ECU
The most medial superficial extensor, running from the lateral epicondyle and ulna to the base of the 5th metacarpal. It extends and adducts (ulnar deviates) the wrist.
Overview
ECU arises from the lateral epicondyle and, by an aponeurosis, from the posterior border of the ulna. Its tendon runs in a groove on the ulnar head within the 6th extensor compartment, held by its own fibro-osseous subsheath. It inserts on the base of the 5th metacarpal. With FCU it adducts the wrist (ulnar deviation), and with the radial extensors it extends it. Its subsheath is part of the triangular fibrocartilage complex, so it also stabilises the ulnar side of the wrist.
Anatomy
- Origin
Lateral epicondyle of the humerus and the posterior border of the ulna.
- Insertion
Base of the 5th metacarpal (medial side).
- Action
Extension and adduction of the wrist.
- Innervation
Posterior interosseous nerve.
- Nerve roots
C7–C8
- Arterial supply
Ulnar artery (posterior ulnar recurrent) and posterior interosseous artery.
Function
- Extends the wrist
- Adducts (ulnar deviates) the wrist
- Stabilises the ulnar side of the wrist
Clinical significance
ECU subluxation and tendinopathy
Rupture of the ECU subsheath, common in tennis and golf players, lets the tendon snap over the ulnar head during forearm rotation, causing ulnar-sided wrist pain.
Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.