The main cause of ‘O’-shaped leg and ‘X’-shaped leg deformities is rickets in children. A small part is due to sequelae caused by cartilage development disorders, fractures, trauma, bone tumors, etc. When children suffer from rickets, due to insufficient calcium, the cartilage of the epiphysis can not be ossified normally, and the original bone is decalcified and absorbed, so the bone is softened and cannot tolerate the action of gravity. In addition, the ligaments around the knee joint are loosened. Loss of the support and protection of the bones, the epiphysis deforms or shifts, and the calf bones are bent and deformed, resulting in ‘O’ and ‘X’ legs.