Which muscle abducts the wrist?

• A. Extensor carpi radialis longus
• B. Extensor carpi ulnaris
• C. Flexor carpi radialis
• D. Palmaris longus

Answer: (A)

Abduction of the wrist means moving the hand toward the thumb side (radial deviation). The Extensor carpi radialis longus is the primary muscle that pulls the hand toward the radius, producing this radial deviation, especially when the wrist is extended. It attaches on the base of the second metacarpal, giving it a favorable line of pull for abduction. In contrast, Extensor carpi ulnaris pulls the hand toward the ulna (ulnar deviation), Flexor carpi radialis mainly flexes the wrist (and can assist with radial deviation in some positions but is not the primary abductor), and Palmaris longus is a weak flexor with little effect on deviation. So the Extensor carpi radialis longus best explains wrist abduction.