Which nerve injury would most likely cause weakness of the wrist extensor muscles?

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

Answer: (C)

Wrist extensor muscles are controlled by the radial nerve. These muscles, located in the posterior compartment of the forearm, extend the wrist, so damage to the radial nerve weakens or prevents this action, often producing a characteristic wrist drop. The median nerve mainly innervates forearm flexors and many hand muscles, so its injury would more affect flexion and fine motor hand function. The ulnar nerve mainly affects certain forearm flexors and most intrinsic hand muscles, not the primary wrist extensors. The axillary nerve serves the deltoid and teres minor, not the wrist extensors. Therefore, injury to the radial nerve best explains weakness of the wrist extensor muscles.