Diagnostic criteria for rheumatoid arthritis: 1. Morning stiffness for at least 1 hour (≥ 6 weeks) 2, Swelling of 3 or more joints (≥ 6 weeks). 3, Swelling of the wrist, metacarpophalangeal joint or proximal interphalangeal joint (≥6 weeks). 4.Symmetrical arthrogryposis (≥6 weeks). 5.Subcutaneous nodules. 6.Hand X-ray changes. 7. Positive rheumatoid factor (titer > 1:32). The diagnosis of rheumatoid arthritis requires four or more criteria. The sensitivity is 93% and specificity is 90%, both better than the 1958 criteria (sensitivity 92%, specificity 85%).