RESUMEN
<p><b>AIM</b>To investigate the effects of extremely low magnetic field on acute and chronic arthritis of rats.</p><p><b>METHODS</b>The acute arthritis animal models were built by the right thenar hypodermic injection of carrageenan. Then they were exposed to magnetic field for 6 hours and 8 hours, respectively. The chronic arthritis animal models were built by the right thenar hypodermic injection of complete freund's adjuvant. They were exposed to magnetic field for 7 days and 6 hours each day after the secondary affection appeared 15 days later. The swelling and inflammatory cytokine were observed in both the acute and chronic arthritis models.</p><p><b>RESULTS</b>The ankle and thenar swellings decreased in both the acute and chronic arthritis models after different time exposure. The cytokine of serum and articular lixivium did not change in 6 hours exposed groups of acute arthritis models. The serum IL-6 and articular lixivium IL-6, TNF-alpha decreased compared with sham groups. Though the rest indexes were unchanged, they had the tendency of decrease.</p><p><b>CONCLUSION</b>The extremely low magnetic field has the effects of restraining acute and chronic arthritis of rats, and can also partially restrain the cytokines when the rats were exposed for 8 hours. The mechanisms need to be further investigated.</p>