Which muscles serve as prime movers for wrist extension?

Which muscles serve as prime movers for wrist extension?

• A. Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis, & Extensor Carpi Ulnaris
• B. Flexor Carpi Radialis & Flexor Carpi Ulnaris
• C. Extensor Digitorum & Extensor Pollicis Longus
• D. Abductor Pollicis Longus & Extensor Pollicis Brevis

Answer: (A)

Wrist extension is produced by the extensor muscles on the back of the forearm that cross the wrist joint. The main drivers are the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris. These muscles attach to the dorsal side of the hand and pull the hand backward to straighten the wrist. The longus and brevis run toward the radial side to extend the wrist, with the longus contributing a bit to radial deviation and the ulnaris contributing to ulnar deviation, working together to lift the hand from a flexed position. Wrist flexion, in contrast, is done by the flexor carpi radialis and flexor carpi ulnaris, which pull the palm downward toward the forearm, not upward. Some other extensor muscles, like extensor digitorum and extensor pollicis longus, do extend the fingers and thumb, and they can influence the wrist position when the fingers are actively extended, but they are not the primary movers for pure wrist extension. The muscles that move the thumb, such as the abductor pollicis longus and extensor pollicis brevis, mainly act on the thumb rather than the wrist itself.

Wrist extension is produced by the extensor muscles on the back of the forearm that cross the wrist joint. The main drivers are the extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris. These muscles attach to the dorsal side of the hand and pull the hand backward to straighten the wrist. The longus and brevis run toward the radial side to extend the wrist, with the longus contributing a bit to radial deviation and the ulnaris contributing to ulnar deviation, working together to lift the hand from a flexed position.

Wrist flexion, in contrast, is done by the flexor carpi radialis and flexor carpi ulnaris, which pull the palm downward toward the forearm, not upward. Some other extensor muscles, like extensor digitorum and extensor pollicis longus, do extend the fingers and thumb, and they can influence the wrist position when the fingers are actively extended, but they are not the primary movers for pure wrist extension. The muscles that move the thumb, such as the abductor pollicis longus and extensor pollicis brevis, mainly act on the thumb rather than the wrist itself.