Upper limb

Extensor Carpi Ulnaris

Musculus extensor carpi ulnaris

Origin

Lateral epicondyle of the humerus (common extensor tendon) and posterior border of the ulna

Insertion

Base of the fifth metacarpal bone

Function

Extends the wrist and moves it into ulnar deviation

Innervation

Radial nerve (deep branch/posterior interosseous nerve), C7–C8

Movement & chain

Works together with extensor carpi radialis longus/brevis as an antagonist of the ulnar wrist flexor; simultaneous activation with flexor carpi ulnaris produces pure ulnar deviation without a flexion-extension component.

Palpation

Easily palpated on the distal, ulnar side of the forearm, just proximal to the ulnar head, during active wrist extension with ulnar deviation.

Clinical

Frequently involved in lateral epicondylitis (tennis elbow) due to the shared origin with the other wrist extensors.

Segmental innervation

Part of the C7–C8 myotome via the deep branch of the radial nerve; loss of function fits with an injury to this nerve, for example in a humeral shaft fracture.

In clinical practice

Focus on hand function and edema prevention; ensure IV cannulas and splints maintain functional hand position to prevent joint contractures.

Region in the model

Upper limb