Avulsion fractures of the anterior inferior iliac spine are rare injuries of the pelvic ring and occur during sports activities. Hereby is presented a case of a 22-year-old professional football player who was diagnosed to have an avulsion fracture of the anterior inferior iliac spine on the right side four months after the initial injury and he was treated surgically with the excision of the avulsed fragment. The football player recovered completely and returned to his usual sports activities. Two years later, due to the pain in the hip an x-ray and MR image were made, which established the existence of crescent formation, a heterotopic bone, in the area of the anterior inferior iliac spine, which was surgically removed. Physical and medical therapy was conducted and after four months, the professional athlete was back playing football. Two years after the surgical excision of heterotopic ossification, the patient was completely asymptomatic with the same ROM without any thigh muscle hypotrophy, although isokinetic muscle testing did show some weakness of the thigh extensor muscles. An x-ray did not show any signs of heterotopic ossification.