Apophyseal avulsion fractures of the anterior inferior iliac spine are rare; they are usually seen in adolescents as a result of sudden contraction of the rectus femoris muscle. Treatment is usually conservative, but surgical management may be necessary in certain circumstances. We present an unusual case of a 14-year-old male who was referred to our department for a suspicious pathological fracture of his right anterior inferior iliac spine; he was found to have an avulsion fracture of the anterior inferior iliac spine due to simple bone cyst. We discuss the treatment of this rare injury caused by a benign osseous tumour.