The severity of knee entropion can be determined by the active knee distance and the normal knee distance, which can be categorized into four degrees based on the size of the active knee distance and the normal knee distance. Active Knee Distance is the distance between the two knees observed when the patient remains standing with the feet, legs, and knees kept together. The normative knee distance is when the patient stands normally, keeping the knee joints and legs relaxed, and observing the distance between the two knees. If the normative knee distance is less than 3cm and the active distance is equal to 0 then it belongs to the first degree of knee entropion. If the normal knee distance is less than 3cm and the active distance is more than 0, it is II degree knee inversion. If the normal knee distance is between 3 and 5 cm, it is degree III knee inversion. A normative knee distance greater than 5 cm is a degree IV knee inversion. Patients should go to the hospital when they have knee inversion, and the doctor needs to judge the severity of knee inversion according to the professional examination, and the patients should avoid blind judgment. In addition, if the patient wants to correct the knee inversion, he should follow the doctor’s instructions for corrective treatment.