Tenderness May Not Be Sign of Inflammation in Established RA, PsA, and OA

In patients with early rheumatoid arthritis (RA), psoriatic arthritis (PsA), and osteoarthritis (OA), joint tenderness may be associated with inflammation; however, in established disease, tenderness may be associated with joint damage and malalignment, according to research results published in Annals of the Rheumatic Diseases.

Both tenderness and swelling constitute disease activity scores for RA and PsA. While joint swelling may be indicative of synovitis, it is unclear whether tenderness without swelling is a sign of inflammatory joint activity.

In this cross-sectional study, the researchers compared inflammation (measured by scored ultrasound grey scale and power Doppler signals) and structural joint damage (measured by x-rays scored for erosions, joint space narrowing, osteophytes, malalignment, and any damage [a combined binary score where the joint was deemed damaged if it had erosions, joint space narrowing, or malalignment]) in tender nonswollen (TNS) vs nontender nonswollen (NTNS) joints of patients with RA, PsA, and OA. Subanalyses were performed on patient groups categorized by disease duration of less than 2 years (early) or more than 5 years (established).

The study included 34 patients with RA (9 early and 14 established), 31 patients with PsA (7 early and 15 established), and 30 patients with OA.

Results indicated that there were no significant differences in ultrasound signals between the TNS and NTNS joints in patients with RA and PsA. The TNS joints were associated with structural joint damage in patients with RA (any damage, P <.01; joint space narrowing, P =.05) and PsA (any damage, P <.01; erosions, P =.03; malalignment, P <.01). In patients with OA, tenderness was associated with inflammation and, to a greater extent, osteophytes and malalignment. These findings suggested that structural damage has more of an impact on joint tenderness than synovitis in RA, PsA, and OA.

An exception was among patients with disease duration of less than 2 years. In age- and sex-adjusted logistic regression analyses, power Doppler synovitis was more common in TNS vs NTNS joints in patients with RA (odds ratio [OR], 2.22; 95% CI, 1.12-4.43; P =.02) and PsA (OR, 3.26; 95% CI, 1.21-8.81, P =.02). In patients with established disease, there was no difference in power Doppler signals between TNS vs NTNS joints in RA (OR, 1.17; 95% CI, 0.65-2.13, P =.60) and PsA (OR, 0.84; 95% CI, 0.46-1.56; P =.59).

Study limitations included the lack of assessment of interphalangeal joints, the exclusion of other potential reasons for tenderness, and the inability to evaluate whether tenderness can predict progression of structural damage.

Researchers concluded, “The results of this study suggest that an interpretation of tenderness in established inflammatory arthritides as sign of inflammation may not be appropriate. In early disease and possibly also for diagnostic purposes, tenderness may be used as a potential sign of inflammation.”

Reference

Gessl I, Popescu M, Schimpl V, et al. Role of joint damage, malalignment and inflammation in articular tenderness in rheumatoid arthritis, psoriatic arthritis and osteoarthritis. Ann Rheum Dis. Published online January 13, 2021. doi:10.1136/annrheumdis-2020-218744