The small bone mass seen under the tip of the fibula is considered to be an avulsion fracture. The small bone mass under the tip of the fibula is an avulsion fracture caused by trauma to the ankle joint, mostly accompanied by lateral collateral ligament or anterior talofibular ligament injuries, and need to take an MRI film to make a clear diagnosis. If the fracture is not obviously displaced, the main conservative treatment is plaster cast fixation for 4~6 weeks, and the fracture line can be removed from the cast to perform functional exercises. If the fracture is displaced, it can be treated with surgery, incision and internal fixation, and if the ligament is damaged, ligament reconstruction surgery should be performed, and rehabilitation training should be carried out under the guidance of the doctor. If the small bone is seen under the tip of the fibula, we can consider the avulsion fracture caused by trauma, according to whether the fracture is displaced or not, we can adopt conservative treatment or surgery.