Fractures of one of the sesamoid bones is often the cause of lameness in race horses. These fractures may occur due to a violent strain or may result from a traumatism. Usually it occurs when the animal is traveling at a fast pace causing unusual movement of the fetlock joint. When a fractured sesamoid occurs the animal bears very little or no weight on the limb. Swelling and possibly some crepitation are noted on palpation. An accurate diagnosis can usually be made with x-ray examination.