O-legs, i.e. inversion of the knee, may be caused by physiological factors, malnutrition, heredity, etc. The correct correction methods include observation and follow-up, conservative treatment, long leg brace correction and surgical correction. 1. Observation and follow-up: physiological O-legs are common in newborns and young children. As the baby stands and walks, the O-legs will gradually disappear, followed by X-legs, and then self-corrected to basically normal with the normal activities of young children. In this case, parents should pay attention to observation and regular follow-up in the hospital. 2. Conservative treatment: If there are symptoms of lower limb pain, conservative treatment can be carried out first, such as reducing the amount of activity. The method of shoe padding on one side is ineffective in the treatment of O-legs and should be avoided. In addition, pay attention to a balanced diet and take calcium and vitamin D supplements as prescribed by the doctor. 3. Long-legged braces: Long-legged braces can be used to correct O-legs in the early stage. If the symptoms cannot be improved after wearing the brace for more than one year, surgery should be considered. 4. Surgical correction: If the deformity is aggravated to the extent that the distance between the knees or ankles is more than 15 centimeters, which seriously affects the child’s walking and growth and development, it is advisable to perform osteotomy to correct the deformity. In addition, where there is a unilateral knee inversion deformity, it is advisable to early surgical treatment. Children with O-legs should go to the hospital in time and receive standardized treatment under the guidance of the doctor.