Unilateral developmental hip dislocation often has multiple deformities at the same time, such as primary or secondary deformity of the lumbar spine, unequal length of the lower limb, secondary deformity of the knee joint, etc., which makes it very difficult to correct and treat. In our clinical work, we found that patients with unilateral developmental hip dislocation tend to self-perceive the limb on the dislocated side as shorter, while the actual measurement is longer in more than half of the cases. Noting this is suggestive for hip preservation or hip replacement surgical treatment.