X-ray of knee entropion mainly shows that the medial joint space gradually narrows or even disappears with the wear and tear of cartilage, and the inner edge of the medial tibial plateau and the medial condyle of the femur appear to have proliferated bony encumbrances. To perform force line measurement, it is necessary to take a film of the whole length of both lower limbs and connect a line from the femoral head to the center of the ankle joint, which is called the force line, and the angle measurement is performed according to the amount of the force line deviation. When correcting the angle measurement, a more ideal position needs to be chosen, usually positioned at 62.5 degrees outside the center. If it exceeds 5 degrees, surgical correction is usually required.