Hip dysplasia is a disease in which the hip joint develops abnormally. It usually results in abnormal joint sounds, asymmetry in the length of both lower limbs, abnormal gait and other symptoms. In infancy, the symptoms are not obvious because the child is not engaged in weight-bearing activities. However, when the child’s hip joint is engaged in some non-weight-bearing activities, he or she may hear a ringing sound at the base of the thigh, which is mainly caused by the abnormal friction of the dysplastic joint bones, ligaments, and joint capsule. As the child develops, it is obvious that the child’s lower extremities are asymmetrical, especially the texture of the hips on both sides is significantly different. Hip dysplasia may present with structural deformities of the hip, with the joint cavity or joint head showing different positions of development. This development may cause abnormal appearance such as external rotation and internal rotation of the affected hip joint, resulting in a lower limb that is different in length from the healthy side. If hip dysplasia is detected in childhood, the child will often have an abnormal gait, such as a sloping gait when walking, or in some cases, a duck walk. Sometimes the abnormal gait becomes more pronounced when the child tries to correct the gait. Hip dysplasia is usually detected during a child’s physical examination, usually early, and the symptoms are relatively mild, and usually the child can be cured through active rehabilitation. So parents should not have too much pressure on their children’s hearts.