O-leg is a clinical condition in which the ankles of the lower extremities come together and the knees do not. X-leg is the name of knee valgus, the clinical manifestation of both lower limbs knee joints together, ankle joints do not come together. In children, there is a process of development from physiological knee inversion to knee valgus and then to normal. The normal range is within 3 cm between the two joints. The normal range is within 3 cm of each other. If there is no significant improvement or even a tendency to aggravate after a period of observation, it is necessary to see a pediatric orthopedic surgeon, and if the epiphysis (growth plate) is not abnormal, it can be treated with orthopedic braces and orthopedic insoles through physical examination and auxiliary tests. The majority of children can be treated with orthopedic braces and insoles.