Reduction of pain-related behaviors with either cold or heat treatment in an animal model of acute arthritis

Objective: To assess the effects of heat and cold on quantifiable pain beha viors in an animal model of arthritis that minimizes the motivational-affec tive component of pain. Design: The effects of superficial heat (40 degrees C) and cold (4 degrees C) on pain behaviors in rats with knee joint inflammation were tested befor e and after induction of inflammation and after treatment with heal or cold . Subjects: Joint inflammation was induced in male Sprague-Dawley nts by intr a-articular injection of the knee joint with 3% kaolin and 3% carrageenan. Main Outcome Measures: Withdrawal latency to heat applied to the paw (PWL) assessed secondary hyperalgesia; spontaneous pain behaviors assessed degree of weight bearing/guarding: and joint circumference assessed joint swellin g. Results: Cold treatment of the inflamed knee joint significantly reversed t he PWL immediately after treatment (p = .003) without affecting spontaneous pain behaviors or joint circumference. In contrast, heat treatment produce d a small but signifi cant decrease in spontaneous pain behaviors (p = .03) without affecting PWL or joint circumference. Conclusion: Acute arthritic pain can be treated with either superficial hea t for reducing guarding or with cold for reducing pain or hyperalgesia outs ide the injury site. (C) 1999 by the American Congress of Rehabilitation Me dicine and the American Academy of Physical Medicine and Rehabilitation.