∙ \-

• Patients with RA who meet ACR 1987 rheumatoid arthritis classification criteria or ACR/EULAR 2010 rheumatoid arthritis Classification Criteria and have knee dysfunction.

⁃ ACR 1987 rheumatoid arthritis classification criteria

∙ morning stiffness lasting at least 1 hour (≥6w)

‣ there are 3 or more joint areas swollen (≥6w)

‣ swelling of the wrist, metacarpophalangeal, and proximal phalangeal joint areas (≥6w)

‣ symmetrical arthrogryposis (≥6w)

‣ hand x-ray changes (at least osteoporosis and joint space narrowing)

‣ positive rheumatoid factor (titer \> 1:32) RA can be diagnosed by meeting 4 of the above 7 items

⁃ ACR/EULAR 2010 rheumatoid arthritis Classification Criteria

∙ Involved joints

∙ \- 1 large joint (0 points)

• 2-10 large joints (1 point)

• 1-3 small joints (with or without large joints) (2 points)

• more than 10 small joints (at least one small joint) (5 points)

‣ Serological indicators

⁃ RF and ACPA negative (0 points)

• RF and ACPA, at least one of which is low titer positive. (2 points)

• RF and ACPA with at least one high titer positive (3 points)

‣ Acute chronotropic reactants

⁃ Both CRP and ESR normal (0 points)

• Abnormal CRP or ESR (1 point)

‣ Duration of synovitis

⁃ \<6 weeks (0 points)

• ≥6 weeks (1 point)

‣ Patients with OA who meet the 1995 Classification Criteria for OA and have knee dysfunction 1995 Classification Criteria for Osteoarthritis of the Knee Clinical criteria

⁃ a. Knee pain most of the time in the last 1 month b. Bone rubbing sound c, morning stiffness ≤ 30 minutes d, age ≥ 38 years e, with bony enlargement Knee OA can be diagnosed if a+b+c+d or a+b+e is met

‣ Age-sex matched healthy volunteers who checked in our hospital.

‣ Age \> 18 years old;

‣ Voluntarily participate in this study and sign an informed consent form