Comparison of pain properties in fibromyalgia patients and rheumatoid arthritis patients.

Pain properties of 50 fibromyalgia patients were examined and compared with pain properties of 50 rheumatoid arthritis patients. In both fibromyalgia and rheumatoid arthritis, pain was bilateral, involved multiple sites, and was of equal intensity (60.8 versus 58.7, respectively, on a scale of 100). Fibromyalgia pain, however, was less localized to the joints and suggested greater spatial diffusion. It involved more kinds of pain experiences (radiating, steady, spreading, spasms, gnawing, unlocalized, pricking, crushing, shooting, pressing, splitting, cramping, nagging, and pins and needles), and was dispersed over larger areas of the body. The anatomic sites best for discrimination between patients with fibromyalgia and patients with rheumatoid arthritis were the lower back, thigh, abdomen, head, and hips for fibromyalgia, and wrist, foot, and fingers for rheumatoid arthritis. The traditional clinical description of aching and stiffness does not appear to accurately describe the complexity of the fibromyalgia pain syndrome.