Ankle fractures that remain anatomically aligned are treated non-surgically with a cast or walking shoe. Unstable fractures at risk of falling out of alignment are often operated on. Around 20,000 people in England are admitted to hospital each year with a broken ankle. In some patients, the instability is clear, for example, with an ankle dislocation fracture. In others, it is less obvious, as in an isolated fracture of the fibula at the level of the syndesmosis (Weber B fractures). Stability in this type depends on the extent of ligament injury, which cannot be easily determined clinically. Clinical assessment, stress radiography, or external tests are used to test for stability.