Tender joints may not always signify active inflammatory arthritis
medwireNews: Among patients with longstanding rheumatoid arthritis (RA) or psoriatic arthritis (PsA), having tenderness in non-swollen joints is not significantly associated with the presence of active inflammation as measured by power Doppler ultrasound, researchers report.
Therefore, tenderness “should not automatically be regarded as a sign of active disease” in patients with established inflammatory arthritis, even though “currently used composite disease activity indices, remission criteria and inclusion criteria into clinical drug trials generally include [tender joint counts],” say Peter Mandl (Medical University of Vienna, Austria) and colleagues.
However, they note that “tenderness may be used as a potential sign of inflammation” in patients with early disease.
These findings are based on an analysis of clinical and ultrasound data from the wrist and finger joints of 34 individuals with RA and 31 with PsA. The majority (53.1%) of RA patients had moderate disease activity, while most (65.5%) of those with PsA had high disease activity; the average disease duration was approximately 7 years.
Of the 745 joints analyzed in the RA cohort, 20.8% were classified as tender non-swollen (TNS), and there was no Doppler signal in 85.8% of these 155 TNS joints. Similarly, there were no Doppler signals in 90.9% of the 219 TNS joints (of a total 682 joints) in the PsA cohort, and there were no significant differences in Doppler signals between TNS and non-tender non-swollen (NTNS) joints in both patient groups.
In a model adjusting for age and sex, there were no significant associations between joint tenderness and Doppler signals of inflammation among patients with a disease duration of longer than 5 years. However, when the analysis was restricted to the nine RA patients (174 joints) and seven PsA patients (138 joints) with a disease duration of less than 2 years, those with a Doppler signal were significantly more likely to have joint tenderness than those without, at adjusted odds ratios of 2.2 and 3.3, respectively.
The researchers say that “[w]hile tenderness in early arthritis may be more related to inflammation, established disease is better explained by joint damage and malalignment.” Indeed, having a positive radiographic damage score – accounting for joint space narrowing, erosion, and malalignment – was significantly associated with tenderness in non-swollen joints in the RA and PsA cohorts, but the damage score was not associated with tenderness in swollen joints.
Mandl and colleagues also evaluated 657 joints from 30 patients with osteoarthritis, “which, despite certain inflammatory features, is nonetheless seen as a primarily degenerative condition,” they explain. The team found that osteophytes were more common in TNS relative to NTNS joints in people with osteoarthritis, but not in those with RA or PsA, indicating “that secondary [osteoarthritis] likely does not explain tenderness in patients with RA or PsA.”
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