Standardization of an experimental model suitable for studies on the effect of exercise on arthritis

OBJECTIVE To standardize an experimental model of chronic monoarthritis induced by complete Freund's adjuvant appropriate for the analysis of the effect of walking on nociception and on joint edema. METHODS The following factors were evaluated as to monoarthritis induction: route and site of administration, number and interval of inoculations, Mycobacterium species, and animal gender. Wistar male and female rats (200 to 250g) received two injections of complete Freund's adjuvant containing Mycobacterium tuberculosis (1.0mg/mL; 50µL) or Mycobacterium butyricum (0.5mg/mL; 50µL) intra-articularly in the tibiotarsal or tibiofemoral joints, or an injection of complete Freund's adjuvant (Mycobacterium butyricum or tuberculosis) intradermally at the base of the tail and another intra-articularly (tibiotarsal or tibiofemoral). The animals were submitted to evaluations of articular disability and edema. Articular disability was assessed by paw elevation time (in seconds) during the one-minute walk test. Edema of the tibiofemoral joint was assessed by variation of joint diameter (cm). Tibiotarsal joint edema was measured by the volume of the paw (mL). RESULTS Administration of complete Freund's adjuvant containing Mycobacterium butyricum increased paw elevation time and edema in both joints. CONCLUSIONS These data allow standardization of an animal model of chronic monoarthritis adequate for analysis of the effects of exercise on treatment of rheumatoid arthritis.