The first conscious symptom of femoral head necrosis is pain, which is around the hip joint, inner thigh, anterior side or knee. In the early stage, the pain starts as vague, dull or intermittent pain, which is aggravated by more activities and can be relieved or reduced by rest. However, there are some cases of persistent pain, whether it is from exertion or rest, or even from lying in bed. Moreover, the pain gradually increases. At this time, although there is no obvious abnormal morphological change on the X-ray, the function of the hip joint is already limited to different degrees. For example, the patient’s hip joint on the affected side is limited in abduction and rotation, and cannot squat in place. At the advanced stage of femoral head necrosis, the femoral head collapses, fractures and deforms, and some of them may cause hip dislocation, and the pain at this time is directly related to hip joint activities and weight bearing. The pain is caused by bony friction in the joint when moving, but the pain is not obvious when there is no friction between the head and socket at rest. Therefore, the pain is aggravated by walking and activity, while the pain is stopped or reduced by movement. In short, the early stage is mainly pain with functional limitation; the late stage is mainly functional impairment with pain. Femoral head necrosis stage I (ultrastructural variant stage): X-ray film shows disorder and fracture of the trabecular structure in the bearing system of the femoral head, with or without limited mild pain at the edges of the femoral head. Femoral head necrosis stage II (sensitized stage).
X-rays show small cystic lesion shadows inside the femoral head with uneven density in the ring area around the cystic lesion area. The bone trabecular structure is disturbed, sparse or blurred. Small collapse may also appear, and the area of collapse may be 10% to 30%. The clinical condition is accompanied by significant pain and slight restriction of movement. Stage III femoral head necrosis (necrotic stage): X-ray shows morphological changes of the femoral head, including incomplete, worm-like or flattened edges, partial loss of trabecular structures, uneven bone density, widening or narrowing of the acetabulum and femoral head gap, and formation of superfluous bone. In stage IV of femoral head necrosis (disabling stage), the morphology and structure of the femoral head are obviously changed, with large irregular collapse or flattening, and the structure of the bone trabeculae is mutated. The gap between the acetabulum and the femoral head disappears, etc. Clinical manifestations include pain, functional impairment, stiffness and inability to walk, dislocation or subluxation, and limited functional activity of the involved knee joint. As osteonecrosis often involves both sides, most patients end up with joint deformity and secondary osteoarthritic changes. Although there are numerous treatment methods available, none of them are sure of their efficacy, making treatment quite tricky. However, it has been proven that the earlier the treatment, the better the results.