Wrist drop is defined as the inability to perform wrist extension or the ability to do so only to a severely limited extent. Clinically, the hand hangs flaccidly. Wrist drop is frequently associated with lesions of the radial nerve.
The more proximal the radial nerve lesion, the more muscle groups are affected. While a distal radial nerve injury generally does not cause wrist drop, an injury in the middle portion of the nerve results in the typical wrist drop and a pronated position of the forearm. If the injury is proximal, extension at the elbow joint is additionally impossible. Grip strength is also reduced with wrist drop because, due to loss of the extensor muscles, the flexor muscles are already shortened at rest.