• Extensor carpi ulnaris extends the wrist joint with slight ulnar deviation.
• Extrinsic extensor muscle.
• Located in the sixth extensor/dorsal compartment.
Muscle Function: Extends and adducts the wrist.
Palpation: Dorsal surface of the wrist crease in line with the fifth metacarpal on the ulnar side of the extensor digit minimi.
Gravity-lessened Test: Position – the subject in sitting with the elbow in slight flexion, forearm in neutral, wrist in flexion. The forearm is positioned resting on the table with the wrist on the edge and the hand off the edge. Stabilize – the forearm and support the hand. Support - the arm through the range.
Anti-gravity Test: Position – the subject in sitting with elbow in slight flexion, forearm in pronation, wrist in flexion. The forearm is positioned resting on the table with the wrist on the edge an the nd the hand off the edge. Stabilize – the forearm and support the hand. Resist – against wrist extension with slight ulnar deviation (in the direction of wrist flexion and radial deviation).
Possible Substitutions: Substitutions include extensor digiti minimi, extensor digitorum communis, extensor carpi radialis, other finger extensor muscles, and flexor carpi ulnaris. To prevent these substitutions, palpate the tendon correctly with resistance against wrist extension and slight ulnar deviation.
• Roots: C6, C7, C8.
• Nerve: Radial nerve, posterior interosseous nerve.
• Innervation Route: C6, C7, C8 → radial nerve → posterior interosseous nerve → extensor carpi ulnaris branch.
Origin: Common extensor tendon from lateral epicondyle of humerus, by aponeurosis from posterior border of ulna and deep antebrachial fascia.
Insertion: Base of fifth metacarpal bone, ulnar side.