Background/Purpose:

OA and RA are among the most common chronic painful rheumatic diseases. Appreciation of the role of pain sensitization in OA has revolutionized the management of chronic pain with neuroactive agents. By contrast, pain in RA has conventionally been considered to be “inflammatory”, with the belief that treatment with disease-modifying anti-rheumatic agents (DMARDs) aborts the painful experience. A number of patients with RA, however, continue to experience pain despite optimal control of inflammation. Thus, we aimed to test the hypothesis that pain in RA, similar to OA, includes signs of peripheral and central sensitization and neuropathic features.

Methods:

After consent, patients with physician diagnosis of symptomatic OA of the hips and/or knees (VAS pain score at the sites ≥3/10), active or DMARD-naïve RA (escalation or change in RA therapy, synovitis on physician exam at the reference clinic visit), and control (45 yrs or older, without pain ≥1 month, no arthritis or neuropathy or joint replacement history) were recruited and asked to fill a painDETECT (PD-Q) questionnaire ¹. Quantitative sensory tests (QST) including pressure pain thresholds (PPT) using an algometer and temporal summation (TS) using von Frey monofilament (60 g), were performed on all subjects at right and left radial styloids, tibial tuberosities, and medial knees. Sensitization is present when there is low PPT using an algometer (peripheral= diseased site; central= no diseased site) and an increased in pain score after repeated controlled stimulation with von Frey monofilament (central) ². Demographic data, PD-Q scores and results from QST were compared between groups using analysis of variance (ANOVA). PD-Q scores were classified as ≤12 -unlikely neuropathic vs >12 –likely neuropathic. Correlations between PD-Q scores and QST results were analyzed using Spearman’s rho.

Results:

Participants included 25 OA, 20 RA, and 19 controls. Patients with OA were older and had higher BMI than RA and control subjects (p <0.001). PD-Q scores were in the “likely neuropathic” range in 32% of OA and 40% of RA vs 0% of control subjects (p<0.001). Both OA and RA had lower PPT vs control at all tested sites. OA and RA patients exhibited significantly higher TS vs control subjects. PD-Q final score and component questions were associated significantly with PPT (rho=-0.244 to -0.448, p<0.05), but not to TS results.

Conclusion:

Both OA and RA exhibited evidence of neuropathic features on a PD-Q questionnaire and peripheral and central sensitization on QST. To our knowledge, this is the first study evaluating sensitization in both OA and RA compared to control and demonstrating similar pain patterns and degrees of sensitization in both disease groups. The clinical and treatment implications of these findings warrant attention and further investigation.

Reference: 1. Curr Med Res Opin, Vol.22, No. 10 (2006); 2. Curr Osteoporosis Rep (2015).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/features-of-peripheral-and-central-sensitization-and-neuropathic-pain-are-seen-in-both-osteoarthritis-and-rheumatoid-arthritis/