The 1987 criteria of the American Rheumatism Association are now commonly used: (1) morning stiffness in or around the joints lasting at least 1 hour per day, with a duration of at least 6 weeks (2) simultaneous soft-tissue swelling or effusion in at least 3 joint areas, for at least 6 weeks (3) swelling in at least one of the carpal, metacarpal, and proximal interphalangeal joint areas, for at least 6 weeks (4) symmetric arthritis, for at least 6 weeks Li, Orthopaedic Department, Nankai Hospital, Tianjin City, China (5) Rheumatoid nodules (6) Hand X-ray changes (at least osteoporosis and narrowing of the joint space) (7) Positive rheumatoid factor (titer > 1:20) Anyone who meets the above 7 items is considered to have typical rheumatoid arthritis; anyone who meets the above 4 items is considered to have definite rheumatoid arthritis; anyone who meets the above 3 items is considered to have probable rheumatoid arthritis; and anyone who meets fewer than 2 of the above criteria but has the following Rheumatoid arthritis is suspected if 2 or more of the above criteria are met (a. morning stiffness; b. persistent or recurrent joint tenderness or pain on movement for at least 6 weeks; c. current or past joint enlargement; d. subcutaneous nodules; e. increased blood sedimentation rate or positive C-reactive protein; f. iritis).