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Extensor Carpi Ulnaris Muscle Anatomy

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Extensor Carpi Ulnaris Muscle Anatomy

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The extensor carpi ulnaris (ECU), a long fusiform muscle located on the medial border of the forearm, it’s one of the posterior compartment of the forearm.

Extensor Carpi Ulnaris Muscle Anatomy

The Extensor Carpi Ulnaris Muscle has two heads: a humeral head from the common extensor tendon and an ulnar head that arises by a common aponeurosis attached to the posterior border of the ulna and shared by the flexor carpi ulnaris, flexor digitorum profundus, and deep fascia of the forearm.

See Also: Forearm Muscles Anatomy & Function

Distally, its tendon runs in a groove between the ulnar head and its styloid process, through a separate compartment of the extensor retinaculum within the tendinous sheath of the extensor carpi ulnaris. It inserts onto the dorsal base of the fifth metacarpal after passing through the sixth compartment of the extensor retinaculum.

See Also: Hand Anatomy, Bones & Muscles
Extensor Carpi Ulnaris Muscle

It receives its innervation from the posterior interosseous nerve a banch of the radial nerve.

It gets its blood supply from the ulnar artery.

Acting with the extensor carpi radialis longus and extensor carpi radialis brevis, it extends the hand; acting with the flexor carpi ulnaris, it adducts the hand. The simultaneous action of extensor carpi radialis longus and extensor carpi radialis brevis along with extensor carpi ulnaris helps to provide medial stability to the wrist while clenching the fist (tight flexion of the medial four digits).

OriginLateral epicondyle of humerus (humeral head) and posterior border of ulna (ulnar head)
InsertionBase of 5th metacarpal
InnervationPosterior interosseous nerve (C7 and C8)
Blood SupplyUlnar artery
ActionWrist extension and wrist adduction

Clinically

Repetitive flexion and extension of the wrist can lead to tenosynovitis due to the irritation of the tendon and the sheath that holds it in place. Overuse can also lead to tendinopathy of the muscle’s tendon, in which there can be thickening and painful stiffness of the tendon with minimal structural damage. Continued excessive stress on the tendon can cause structural damage, which can lead to a partial tear.

To test the extensor carpi ulnaris, the forearm is pronated and the fingers are extended. The extended wrist is then adducted against resistance. If acting normally, the muscle can be seen and palpated in the proximal part of the forearm and its tendon can be felt proximal to the head of the ulna.

References & More

  1. Clinically Oriented Anatomy – 8th Edition
  2. Clinical Anatomy by Regions, Richard S. Snell.
  3. Sawyer E, Sajjad H, Tadi P. Anatomy, Shoulder and Upper Limb, Forearm Extensor Carpi Ulnaris Muscle. [Updated 2023 Aug 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed
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