The cause of ankle bone protrusion may be normal anatomical structure, or related to congenital developmental deformity of bones, fracture deformity healing and other diseases. 1. Normal anatomical structure: for example, it is generally located in the inner and outer ankle joint, symmetrical existence of the inner and outer ankle, no local pain, swelling performance, is a normal anatomical structure. 2. Congenital developmental deformity of bones: this condition is usually found in childhood and does not change significantly with the passage of time. 3. Fracture deformity healing: a protrusion occurs after localized fracture deformity healing, there is a clear history of trauma and fracture, and there are usually no other obvious symptoms after fracture healing. 4. Other diseases: ankle free body, osteochondroma, bone cyst and other lesions. The free body will move, so sometimes it may disappear, while osteochondroma, bone cysts and so on may be accompanied by local pain or pressure pain, which can be examined and judged by the nature of the protrusion through the ankle joint front and side view film. If you have a protruding ankle bone with obvious discomfort symptoms, it is recommended to go to the hospital in time, complete the relevant examinations, clarify the cause of the disease and then follow the doctor’s instructions to carry out targeted treatment, so as to avoid delaying the condition.