What injury is most likely associated with an inability to extend the wrist and MCP joints?

Inability to extend the wrist and metacarpophalangeal (MCP) joints typically indicates a dysfunction of the radial nerve. The radial nerve is responsible for the innervation of the muscles responsible for wrist and finger extension. When this nerve is injured, it leads to a condition known as wrist drop, where the individual cannot extend their wrist or fingers.

The radial nerve primarily traverses the posterior aspect of the arm and forearm and is the main motor nerve for the extensor muscles. In a scenario involving radial nerve injury, the affected individual would lose the ability to actively extend these joints, resulting in the clinical presentation referred to previously.

Other nerve injuries, like those of the ulnar or median nerves, would present differently. For instance, ulnar nerve injury affects the function of the intrinsic muscles of the hand, leading to difficulties with gripping and finger abduction/adduction but typically sparing wrist extension. Similarly, median nerve injury results in the inability to specifically oppose the thumb and affects the ability to flex the wrist and fingers, but does not impair the ability to extend them. Musculocutaneous nerve injuries primarily affect flexion at the elbow, not extension at the wrist or fingers.

Hence, the nature