Wrist drop, also known as radial nerve palsy, is a condition where a person cannot extend their wrist and it hangs flaccidly. To demonstrate wrist drop, hold your arm out in front of you with your forearm parallel to the floor. With the back of your hand facing the ceiling (i.e. pronated), let your hand hang limply so that your fingers point downward. A person with wrist drop would be unable to move from this position to one in which the fingers are pointing up towards the ceiling.