A lot of children who injure their ankles come to the emergency department for an evaluation, and often an X-ray of the ankle is obtained to determine if a bone fracture is present. In more than 85% of cases, however, the injury is a sprain and not a bone fracture and can be treated with rest, ice, elevation, and pain medications. X-rays obtained in the emergency departments are time consuming, often uncomfortable for the patient, and expose children to radiation, the long-term effects of which are not yet fully understand by doctors or scientists. Bedside ultrasound is a non-invasive and a non-painful device that does not produce radiation. It was been shown to determine the presence of bone fracture in childrens' wrists and forearms just as well as X-rays do. In our study, the investigators would like to determine if a bedside ultrasound can also be used to evaluate ankle fractures in children.