Ankle sprains are a common sports-related injury and account for 5% of all emergency department visits. There is a high probability of a fracture If a patient meets the criteria of Ottawa's rules. However, if no fracture is evident on x-ray, then extra-articular swelling directs the clinician to the diagnosis of an ankle sprain since ligaments are not visible on radiographs. Swelling on an ankle x-ray is best identified by asymmetry of soft tissue thickness when comparing the medial and lateral side of the foot.