Table 1 Diagnostic criteria for KOA according to the Chinese Medical Association Orthopaedic Branch (2007 revision)

1. Repeated knee pain in the last month

2. X-ray film (standing or weight-bearing position) shows narrowing of joint space, subchondral bone sclerosis and/or cystic changes, joint edge formation

3. Joint fluid (at least two times) clear, viscous, WCC < 0.002 × 10⁹/L

4. Middle-aged or elderly patients (≥ 40 years old)

5. Morning stiffness ≤ 3 min

6. Bone friction sound (feeling) during activity