There are many reasons for the phenomenon of one long leg and one short leg in the clinic, for example, if this phenomenon occurs in infants and young children, it may be due to congenital acetabular dysplasia, which should be reset in time, and fixed by using herringbone cast. If this phenomenon occurs in adults, it may be due to the occurrence of femoral stem fracture or tibial or fibular fracture, due to the position of the fracture end is not ideal, shortening deformity, this phenomenon occurs, in the treatment can be taken as a manipulation of reset or surgical incision and reset to give immobilization. In addition, if the patient has femoral head necrosis, especially in the late stage of femoral head necrosis, the femoral head collapses, there is dead bone formation, and the affected limb is also shortened, X-ray film can make a clear diagnosis, and most of the treatment adopts surgical treatment, which can be considered as artificial total hip arthroplasty.