OBJECTIVE: Heat therapy is one of physical therapies used most commonly in chronic osteoarthritis. The therapeutic effects of heat therapy might be attributed to induce heat shock proteins in heat-stimulated cells and tissues and therefore, to inhibit cellular damages due to inflammation. In order to investigate preliminarily the therapeutic effects of heat therapy, Hsp(heat shock protein) 70 expressions by heat stimulation were measured in cultured chondrocytes and knee joint cartilages of rabbits. METHOD: Five rabbits were used in total in this study. Three rabbits were used for chodrocytes culture and two rabbits were in vivo study. Chondrocytes were cultured from knee cartilages of three rabbits and treated at 33degreesC, 37degreesC, and 42degreesC for 20 min. In order to clarify whether heat therapy using ultrasonification can induce Hsp 70 expression in cartilage tissues, right knees of rabbits were heat-stimulated by ultrasonification for 20 min and their left knees were untreated. After 2 hours, cultured chondrocytes and cartilages were prepared and Hsp 70 expression was also observed by Western blot analysis. RESULTS: Hsp 70 expression was increased 1.48 folds in 42degreesC treated cells compared to in 37degreesC treated cells. The heat-stimulated cartilages showed 1.65 fold increases in Hsp 70 expression compared to the unstimulated cartilages. CONCLUSION: Hsp 70 expressions were increased by heat stimulation in cultured chondrocytes as well as in cartilage issues.