Which two muscles are the primary wrist flexors on the anterior forearm?

• A. Flexor carpi radialis and flexor carpi ulnaris
• B. Flexor digitorum superficialis and flexor digitorum profundus
• C. Extensor carpi radialis longus and extensor carpi radialis brevis
• D. Palmaris longus and flexor pollicis longus

Answer: (A)

The main action tested is identifying the primary wrist flexors on the anterior forearm. The two muscles that do most of the work across the wrist are the flexor carpi radialis and the flexor carpi ulnaris. They run on the front side of the forearm and pull on the bases of the hand’s metacarpals to bend the wrist forward. Flexor carpi radialis mainly flexes the wrist and helps with radial (thumb-side) deviation, while flexor carpi ulnae flexes the wrist and helps with ulnar (pinky-side) deviation. Together they are the primary contributors to wrist flexion, and they share a common origin from the medial epicondyle of the humerus, via the common flexor tendon.

Flexor digitorum superficialis and profundus primarily flex the fingers, with wrist flexion as a secondary or assisting action, so they’re not the main wrist flexors. Extensor carpi radialis longus and brevis are on the posterior forearm and extend the wrist (and can aid with radial deviation), not flex it. Palmaris longus is a variable, often weak wrist flexor and mainly tenses the palmar fascia, so it isn’t a primary wrist flexor.