Extensor carpi ulnaris
On the ulnar side of the forearm lies the extensor carpi ulnaris muscle. This muscle is responsible for the extension and adduction of the wrist, or carpus. It originates on the outside of the elbow on the lateral epicondyle of the humerus and crosses the forearm downward to insert at the base of the pinky finger, or the fifth metacarpal. Supplied by the ulnar artery and innervated by the radial nerve, the extensor carpi ulnaris muscle works in conjunction with the flexor carpi ulnaris muscle during the adduction of the wrist. However, the extensor carpi ulnaris muscle is the only muscle responsible for ulnar deviation, or movement of the hand sideways in the direction of the pinky. The extensor carpi ulnaris muscle is the muscle most commonly used when accelerating a motorcycle. It is often affected by tendonitis and tennis elbow. This muscle can be strengthened with a resistance band by holding one end of the band in the hand, resting it on the thigh, and placing the other end under the foot. The wrist is then pulled back and slowly returned to its starting position.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Extensor carpi ulnaris