The purpose of this study was to clarify the effects of thermal therapy on pain and inflammation in the inactive phase of Rheumatoid Arthritis (RA) by using rats with adjuvant arthritis (AA). Ankle joint arthritis in the rats was induced by injection of complete Freund’s adjuvant (CFA). Thermal therapy (20 or 60 min/day, 5 days/week) was begun in the chronic phase of AA (4 weeks after CFA injection) and was performed by using a 3-cm-deep hot water bath at 40 ℃. The thermal therapy period was 4 weeks. Ankle volume, erythrocyte sedimentation rate (ESR), plasma concentrations of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6), and mechanical hyperalgesia were determined. No significant changes in ankle volume and ESR were observed. Although mechanical hyperalgesia was aggravated temporarily just after thermal therapy, the longitudinal change in mechanical hyperalgesia was not affected throughout the thermal therapy period. The TNF-α and IL-6 levels were increased partly owing to the thermal therapy. Our data showed that thermal therapy was not effective as well as not noxious for pain and inflammation in the inactive phase of RA. Our data showed that thermal therapy was neither as well as not noxious for pain and inflammation in the inactive phase of RA.
