Etanercept treatment attenuates mechanical and thermal hyperalgesia, with little effect on swelling and histological damage. (a) Prearthritic etanercept treatment in rats with arthritis induced by complete Freund's adjuvant (CFA) reduced paw swelling significantly, by 10%, until 4 days after inflammation induction (n = 4). Thermal (b) and mechanical (c) hyperalgesia were assessed throughout the study. (b)Both prearthritic and postarthritic etanercept therapy abolished thermal hyperalgesia 7 days after inflammation (n = 4). (c) Prearthritic etanercept treatment reduced mechanical hyperalgesia significantly throughout the period studied, and postarthritic treatment reduced hyperalgesia to a lesser extent. (d) Joints were stained with haematoxylin and eosin and were assessed on a 4-point scale (where 0 = absent, 1 = mild, 2 = moderate, 3 = severe) for severity of inflammatory infiltrate, bone necrosis, and cartilage damage. CFA induced inflammatory infiltration 3 days (not shown) and 7 days (d) after CFA, while bone and cartilage were largely preserved. We found no reduction in histological score with either etanercept treatment regime. *P < 0.05; ***P < 0.005 in comparison with controls.