Small joint synovitis in rheumatoid arthritis: should it be assessed separately?

In the assessment of disease activity in rheumatoid arthritis (RA) small joint synovitis is traditionally included only as a component of active, tender or swollen joint counts. By contrast, in the assessment of disease damage in RA, the X-ray score of hands and feet represents one of the most common parameters used and is regarded as a major indicator of outcome. Data presented in this study lead us to hypothesize that the small joints require separate assessment in any study of disease activity or outcome in RA: (i) there is clear evidence that small joint synovitis often occurs in the absence of an abnormal acute phase response (ESR or C-reactive protein) and (ii) measured synovitis is an individual (PIP) joint has been shown to be reliable and to be related to subsequent X-ray changes in the same joint. Our findings show that, in a study of a treatment of RA, it is quite possible for disease activity measures to appear controlled while inflammation continues in the small joints causing radiological damage. This radiological damage is reflected as an adverse outcome. Hence the paradox of improving disease activity but not outcome. We argue that small joint inflammation and damage should be recognized as one aspect of the RA disease process offering unique information and as such should be assessed independently.