Children with O-shaped legs at 5 months of age are usually normal, but may also be pathologic. Most of the children before the age of one have physiological leg curvature, which is related to the special physiology of children, with the normal growth and development of children, this situation will slowly return to normal. Of course, we can’t rule out pathological factors, such as rickets caused by vitamin D deficiency, which is an abnormal condition. O-shaped leg is clinically known as inversion of the knee, at the latest around the age of three years, the inversion of the knee will tend to normalize, generally do not need to intervene too much, but due to pathological factors caused by inversion of the knee, only after the removal of the causative factors, the symptoms of inversion of the knee can be relieved. Parents are advised to monitor the development of the child’s legs carefully and to seek standardized treatment in the hospital if necessary.