Wrist drop results from injury to which nerve?

• A. Radial nerve
• B. Median nerve
• C. Ulnar nerve
• D. Axillary nerve

Answer: (A)

Wrist drop happens when the nerve that powers the wrist extensors in the forearm is damaged. The radial nerve supplies the extensor muscles of the wrist and fingers (via its posterior interosseous branch). When this nerve is injured, these extensors cannot contract to straighten the wrist, so the hand rests in a flexed position at the wrist— producing the classic wrist drop. This pattern commonly results from radial nerve injury in the arm or forearm. Injuries to the median, ulnar, or axillary nerves affect different muscle groups and don’t primarily cause a failure to extend the wrist.