A broken ankle is also known as an ankle fracture. This means that one or more of the bones that make up the ankle joint are broken.
A fractured ankle can range from a simple break in one bone, which may not stop you from walking, to several fractures, which forces your ankle out of place and may require that you not put weight on it for a few months.
Simply put, the more bones that are broken, the more unstable the ankle becomes. There may be ligaments damaged as well. The ligaments of the ankle hold the ankle bones and joint in position.