O-leg is usually an inversion rather than an eversion of the knee joint and can be either congenital or secondary. Acquired factors usually include bone damage, rickets, and osteoarthritis, which can lead to inversion of the knee joint and can be combined with osteoarthritis of the knee joint, which can lead to knee pain. In most cases, the underlying lesion of the inversion deformity can be detected by x-ray, the force line of the measured lower extremity will be significantly altered, and the normal physiological valgus angle will be lost. Patients usually require surgical treatment to correct this, especially in adult patients, and the lower extremity force line abnormality can be resolved by wedge osteotomy. Adolescent patients, on the other hand, can be fixed with corrective braces initially, which can moderately correct the O-leg.