Patients with rheumatoid arthritis are more tender than those with psoriatic arthritis

Articular and nonarticular tenderness was examined in 51 patients with rheumatoid arthritis (RA) and 50 patients with psoriatic arthritis (PsA) by scored palpation and dolorimeter readings. Fifty-seven percent of patients with RA had 10 or more tender fibrositic points vs 24% of patients with PsA (p = 0.0008). Thresholds of tenderness measured by dolorimetry of 6 fibrositic point sites were 3.97 (1.99) [mean (SD)] for RA vs 5.95 (2.28) for PsA (p < 0.0001). Thresholds over actively inflamed joints were 4.19 (1.53) for RA vs 6.78 (2.55) for PsA (p < 0.0001). In both RA and PsA, fibrositic sites were more tender than actively inflamed joints (p < 0.0001). Nonarticular control sites were also more tender in subjects with RA with dolorimeter thresholds at 5.99 (1.96) in RA vs 7.58 (1.60) in PsA (p < 0.0001). These data demonstrate that actively inflamed joints, fibrositic and control nonarticular sites were all more tender in patients with RA than PsA. Both groups were similar in their disease duration and clinical assessments of joint inflammation and damage. We suggest that there may be a disease specific diffuse increase in tenderness in patients with RA, which is not related to joint inflammation. Similarly, the severity of articular inflammation may be underestimated in subjects with PsA.