Figure 1 Upright position X-ray of patients with different Kellgren-Lawrence grades of knee osteoarthrosis.(A) Grade I, slight narrowing of knee joint space with suspicious osteophyte formation, and the patient was defined as early-stage; (B) Grade II, moderate narrowing of knee joint space with small osteophyte formation, and the patient was defined as mid-stage; (C) Grade III, obvious narrowing of knee joint space with moderate osteophyte formation, and the patient was defined as mid-stage; (D) Grade IV, severe narrowing of the knee joint space and massive osteophyte formation, and the patient was defined as end-stage.