O-leg refers to the situation that children's legs are close together, toes are up, knees are up, and the distance between knees is obviously greater than the distance between ankles. We call them O-legs. The treatment of O-leg mainly depends on its severity. If the distance between the knees is 0 to 5 cm, we know it is mild. These children, if they are infants, preschool children or teenagers, can observe with or without physical equipment. For children of 5- 10cm, we will recommend that children wear physical equipment at night. If children can wear it 24 hours a day, the effect is of course better. But for children over 8 years old to 10 cm, we will have surgical treatment. There are many surgical treatments. For older children, one-time result correction can be carried out, and for younger children, bone adjustment treatment can be carried out.