Para-articular ossification of the hip joint represents a severe complication after hip surgery for joint replacement or various forms of trauma. It is always accompanied by tremendous loss of function and is therefore disabling for the patient. The results of past years have drastically reduced this complication in high-risk groups-recurrent joint replacement, acetabular fractures, severe head injuries-by means of hip irradiation and non-steroidal anti-inflammatory medication. In cases, in which significant functional disability results from heterotopic bone formation, it is possible to restore function of the hip joint through surgery. The diagnostics, preoperative planning, surgical therapy, and postoperative treatment protocol are presented.