Which nerve, if injured, can cause wrist drop?

Wrist drop occurs as a result of weakness or paralysis of the extensors of the wrist and fingers, which is primarily controlled by the radial nerve. This nerve is responsible for innervating the muscles that extend the wrist and fingers, allowing for the proper function of hand positioning and grip. When the radial nerve is injured, the individual loses the ability to extend the wrist and fingers, leading to the characteristic "wrist drop" posture where the wrist hangs in a flexed position.

The radial nerve can be injured in several ways, including direct trauma, compression in areas such as the mid-humerus (often referred to as "Saturday night palsy"), or during surgical procedures. Restoration of nerve function and understanding the injury's implications for wrist function is critical for rehabilitation and recovery.

Other nerves, such as the median and ulnar nerves, primarily affect hand movements differently—median nerve injuries cause difficulty with thumb opposition and flexion of the first two fingers, while ulnar nerve injuries impact the ability to perform fine motor tasks and grip strength without causing wrist drop. The axillary nerve is related to shoulder function and would not contribute to the inability to extend the wrist. Therefore, the radial nerve is the correct choice when considering the specific function