Many parents worry about whether their children are X- or O-shaped legs, but the legs of newborn babies are definitely somewhat “O” shaped, which is commonly known as “rotund legs”. But when the child grows to 1 year old, both legs still look like “O” legs; then, the mother is a little anxious, thinking that the child has taken calcium tablets, vitamin D is also eaten according to the rules, diet is also very careful, how can this be? If you go on to become a rotund leg, what can you do when you grow up? 1, “O” and “X” leg is how O-leg: medically known as knee inversion, commonly known as “rotund legs”, is at the knee joint, the shin bone of the lower leg rotated inward an angle This is called “inversion of the knee”. X-leg: medically known as knee valgus, refers to the two feet side by side, both knee joints touching together, and the two feet can not be close to the inner ankle. 2, the newborn “O” leg is a normal physiological phenomenon in the fetal period, the normal fetal position in the uterus, the whole body coiled, the spine slightly forward curved, the limbs flexed tightly crossed in front of the chest and abdomen. The fetus adapts to the small space of the uterus by being as small as possible. Because the fetus in the mother’s womb in this special position, so most newborns are born “O” leg, until the entire baby stage, the medical bend of the lower limbs called physiological bending, which is a normal physiological phenomenon. 3, the baby to a few years old to stabilize the leg shape in learning to walk within 6 months because of the lower limbs to bear the weight of the whole body, so in the appearance of “O” leg more serious, reaching a peak at about 1.5 years old. Subsequently, due to factors such as growth and development, weight bearing and postural changes, the “X” leg gradually develops until the age of 3 to 4 years old, and then begins to correct after the age of 4 years old, and is close to normal by the age of 6 to 7 years old. The normal X-leg phenomenon is maintained from the age of four to seven years until adolescence, with an angle of about 5 to 6 degrees in the lower extremities. Therefore, according to this situation, most infants and children seem to have “O” or “X” shaped legs, but in fact, it is a normal phenomenon in the development process, so parents can not worry. 4. Preventive work is more important than anything else Children need to be properly supplemented with vitamin D after birth, especially for children born in autumn and winter. Avoid letting your child stand or walk too early, and don’t let your child play with a walker too early before he or she learns to crawl. It is also very important that children sit properly and do not take a squatting or kneeling position for a long time. If the deformity of the legs is found during the active stage of rickets, the child needs to receive regular treatment of the rickets system, and if the rickets has developed to the sequelae stage, it is more difficult to treat, and it is necessary to ask a pediatric orthopedic surgeon to help deal with it.