Patellofemoral arthritis is generally referred to as knee osteoarthritis, which can be categorized into 5 stages according to clinical symptoms and X-ray manifestations, including Stage 0, Stage I, Stage II, Stage III and Stage IV. 1. Stage 0: This stage belongs to mild arthritis, the symptoms are not obvious at present, and there is no abnormality through X-ray examination. 2. Stage I: Mild hyperplasia, or narrowing of the patellofemoral joint space, and a mild degree of joint pain are shown through X-ray examination. 3. Stage II: X-ray examination reveals moderate joint narrowing with bony encumbrances, and most patients have obvious pain in the joint at this stage. 4. Stage III: X-ray examination reveals more bone capillaries, accompanied by severe stenosis, and the pain is obviously aggravated. 5. Stage IV: X-ray examination suggests that the degree of patellofemoral joint stenosis is obviously aggravated, and accompanied by osteosclerosis, the pain is more intense, manifested as persistent. According to the symptoms and X-ray examination to diagnose and identify the patellofemoral arthritis belongs to several stages, understand the severity of the disease, and then carry out regular treatment.