Rheumatoid arthritis, the major crippling illness among chronic rheumatic disorders, is a systemic disease that affects many joints with an inflammatory reaction lasting months or years. Frequently, the small joints of the hands and feet are affected first, although often the larger peripheral joints of the wrists, hips, knees, elbows, and shoulders are involved as well. Some remissions do occur, but the illness progresses to produce damage and deformity. There is no known etiology.

In 1961, the American Rheumatism Association developed a set of eight diagnostic criteria for rheumatoid arthritis suitable for epidemiological surveys. They are as follows:

1. Morning stiffness

2. Pain on motion or tenderness in at least one joint

3. Swelling (soft tissue) of at least one joint

4. Swelling of at least one other joint

5. Symmetrical joint swelling

6. Nodules under the skin, typically on the surface of muscles that extend or stretch the limbs

7. Observable changes identified by X-rays, typically erosions of bone

8. Positive serologic test for rheumatoid factor

In a given patient, a definite diagnosis of rheumatoid arthritis would depend on the presence of at least five of these criteria and the absence of evidence for other rheumatic conditions.

Distribution and Incidence

When using the above definition, a number of researchers have indicated that rheumatoid arthritis is worldwide, affecting all ethnic groups. A summary of prevalence data in rheumatoid arthritis has been provided by P. D. Utsinger, N. J. Zvaifler, and E. G. Ehrlich (1985). Fifteen studies were cited from countries such as the United States, United Kingdom, Finland, Puerto Rico, Canada, Japan, Bulgaria, and Jamaica.