Patients included in the research group and in the control group will undergo an "Operating Table Position Simulating " radiograph of the pelvis. The radiograph will be done in the following manner: the patient will be potisioned on the non-operated side in such way that his pelvis is perpendicular to the table. The legs are flexed in 30 degrees at the hip joints and 30 degrees at the knees. The plate with a grid will be placed behind the pelvis in a device with notches (which can be used to measure the angles later). After the total hip replacement the patients will undergo an A-P radiograph of the hip joints while lying on the back with the hip joints bent to 30 degrees to overcome the forward tilt of the pelvis. All of the radiographs will be performed in the presence of an orthopedic surgeon.