What is an action of palmaris longus?

• A. Flex the wrist
• B. Extend the wrist
• C. Abduct the wrist
• D. Adduct the wrist

Answer: (A)

This question is testing what palmaris longus does at the wrist. Palmaris longus is a slender muscle in the superficial front of the forearm, and its tendon runs to the palmar aponeurosis. Its main action is to flex the wrist, though it acts as a relatively weak wrist flexor compared with other forearm muscles. It also tenses the palmar fascia, helping to tighten the palm and improve grip.

Because extending the wrist is the job of the extensor muscles on the back of the forearm, and abducting or adducting the wrist (radial or ulnar deviation) are actions produced by other muscles in the forearm, those options don’t reflect palmaris longus’ primary role. Keep in mind that palmaris longus can be absent in some people, but when present it contributes to wrist flexion and palm tension.