Are parents always troubled by their children’s legs not being straight? Is baby’s O-shaped leg X-shaped leg a disease? Do you need to treat it? In fact, before the age of 7, O-leg and X-leg are not necessarily a disease, but a normal physiological phenomenon. In fact, there is a process for the development of the child’s legs: before 1.5 years old, the infant’s legs are turned inward at about 15°, which looks like O-leg; at about 1.5 years old, the legs are gradually turned outward and become straight, which turns into straight legs; from 3 to 6 years old, the legs start to turn outward, which looks like “X-leg”; by the time the baby is 7 years old, he or she basically has adult legs. At the age of 7, the legs basically have the shape of an adult. Most of the “O-leg” and “X-leg” that children show at different stages will correct themselves and generally do not require special treatment, as long as they pay more attention to observation. If the child has bilateral bending asymmetry and heavy bending, parents should pay attention to it, because it may be pathological “O-leg” and “X-leg”. It is recommended that parents take their baby to a professional pediatric orthopedic surgeon for consultation.