A stress fracture is a tiny crack in the bone caused by repetitive overload. Ankles and feet are the most common sites of stress fractures. People who suddenly begin a serious walking or running program without gradually building up to it are prime candidates for stress fractures. So are people who quickly increase the intensity or distance of their exercise or who switch from running on soft surfaces to hard surfaces.
As with other types of fractures, pain and swelling are common, but the symptoms develop more gradually and are less severe than with a fracture due to a direct blow. The pain gets worse as you put weight on your feet, and is relieved by rest. Your physician will generally diagnose a stress fracture with a physical exam. Casts are not usually required for stress fractures, although your physician will likely recommend a slow progression of return to activity and intensity to allow your body to heal.