For the causes of bone protrusion on the back of the foot, the specific reasons are as follows: 1, the foot appendage has been injured: for example, the foot appendage joint dislocation or fracture, if there is osteophyte during the fracture healing period, the back of the foot will appear bony protrusion, the protrusion is hard, you can clarify through X-ray, CT examination to clarify whether the protrusion is bony or non-bony. 2, tendon sheath cyst: in some patients, the tendon sheath cyst is hard in texture and feels like bone If the cyst is filled with liquid, it is usually caused by non-bone. 3. Osteochondroma: Osteochondroma is mainly a local cortical bone that bulges outward and proliferates, thus forming superfluous bone, which can be clarified by X-ray and CT examination.