An ankle sprain refers to tearing of the ligaments of the ankle. The most common ankle sprain occurs on the lateral (outside) part of the ankle. There's a good chance that while playing sports as a child or stepping on an uneven surface as an adult you sprained your ankle—some 25,000 people do it every day. It can happen in the setting of an ankle fracture (i.e., when the bones of the ankle also break). Most commonly, however, it occurs in isolation.