Can Ultrasound Identify Synovitis?

Kevin Deane, MD


April 15, 2013


Ultrasound may be a major advance in the management of rheumatoid arthritis and other inflammatory joint diseases, and a take-home point from this study is that ultrasound may be particularly useful in the identification of synovitis in MTP joints and shoulders, where clinical joint examination may be less sensitive. However, there are still multiple issues related to ultrasound in clinical rheumatology practice that need to be resolved. It is difficult to evaluate the sensitivity and specificity of ultrasound compared with clinical joint examination in the absence of a "gold standard" for synovitis that can easily be obtained in clinical studies. Certainly, ultrasound findings of synovitis that correlate with poor outcomes in longitudinal evaluations suggest that these findings are a reasonable surrogate for true disease activity.[4] But, to truly understand what ultrasound reveals about inflammatory joint activity, do we need more data comparing ultrasound with synovial biopsy? Furthermore, is a definition of synovitis based on an ultrasound score of ≥ 1 too sensitive? Le Boedec and colleagues found that ultrasound was not more sensitive than clinical joint examination if an ultrasound score of ≥ 2 was used to define synovitis, suggesting that mild synovitis comprises most of the discrepant findings between clinical joint examination and ultrasound. As such, are more studies specifically evaluating the diagnostic accuracy of ultrasound for mild synovitis necessary?

This is an extremely important area because the rheumatology community is working to diagnose and treat rheumatoid arthritis earlier, and mild synovitis that could preferentially be detected by ultrasound rather than clinical joint examination may comprise much of early disease. Moreover, although ultrasound may identify synovitis in joints that do not have swelling on clinical joint examination, what about tenderness? Absence of tenderness and swelling on examination could be highly predictive of absence of synovitis. Finally, are ultrasound findings reliable in a variety of clinical settings, where those who are performing the ultrasound (eg, rheumatologists) may not have the same degree of training as those who participated in published studies? Let us hope that these issues will be addressed soon so that the rheumatology community will have a full understanding of the potentially important role that ultrasound plays in routine clinical practice.