Which motor function is affected by a median nerve injury?

The median nerve plays a crucial role in the motor function of several muscles in the hand and forearm. When a median nerve injury occurs, one of the most significant impacts is on the muscles responsible for thumb movements, particularly pinch and opposition.

The ability to pinch and oppose the thumb involves the action of specific muscles innervated by the median nerve, such as the opponens pollicis and the abductor pollicis brevis. These muscles are vital for grasping and pinching actions, which are essential for various daily tasks, including holding objects and performing intricate movements with the fingers.

In contrast, little finger adduction is primarily controlled by the ulnar nerve, while wrist extension is mainly governed by the radial nerve. The extension of the index finger involves the extensor muscles that are also solely innervated by the radial nerve. Therefore, the correct response highlighting the motor function impacted by a median nerve injury is the ability to perform thumb pinch and opposition.