1. The patient with knee pain has 3 of the following 7 items: ① Age 50 years. ②Morning stiffness <30min. ③Bone rattling sound during joint movement. ④The examination of the knee shows bony hypertrophy. ⑤ There is bone pressure pain. ⑥No significant synovial warming. ⑦There is bone redundancy formation on radiological examination. 2. The patient with knee pain has 5 of the following 9 items: ① Age 50 years. ②Morning stiffness <30min. ③Bone rattling sound during joint movement. ④Knee examination shows bony hypertrophy. ⑤ There is bone pressure pain. ⑥No significant synovial warming. ⑦ESR <40mm/h. ⑧Rheumatoid factor (RF) <1:40. ⑨Sign of osteoarthritis in synovial fluid.