Radiological findings in the rheumatoid knee joint in a seventeen-year follow-up.

In 1967 a population survey of rheumatoid arthritis (RA) was carried out in Stockholm. In a sample of 15,268 subjects, 239 were found to have RA. In 1983, i.e. 17 years later, all the 127 subjects still living could be traced, 109 of them were re-examined and 98 radiographed. Whole-leg weight-bearing radiographs of the 168 knee joints were available for determination of the HKA (Hip-knee-ankle) angle and of the articular space. In this sample, which represented the epidemiological spectrum of RA, disease activity could be associated with radiologic changes in the knee joint, e.g., erosions, cysts and sclerosis. These radiologic findings were predictable owing to the fact that New York criterion no. 3 or 4 for RA had been fulfilled 17 years earlier. In 52% of those with active RA at the follow-up, the articular space was seen to be narrowed. A certain varus angulation (2.2 degrees) was ascertained in the joints of subjects with inactive RA, while this angulation was less pronounced (0.7 degrees) in knee joints of subjects with an active disease.