Clinical course of collagen-induced arthritis. (a) Arthritis score was evaluated at day 0 and day 14 (first and second collagen injections) and then every three days after disease onset (days 17, 20, 24 and 27). Methotrexate (MTX) treatment resulted in a significantly lower arthritis score than recorded for the control or zoledronic acid (ZA) groups. Arthritis score was also decreased by ZA + MTX, but the difference with the control group was not statistically significant. ZA had a slight pro-inflammatory effect, whether used alone or in combination with MTX. (b) Body weight (g) measured at each clinical evaluation. After arthritis induction, the body weight reached a plateau from day 15 with no significant difference between all groups assessed. (c) Paw swelling in rats was assessed by caliper measurement at termination according to the treatments. MTX resulted in a significantly greater reduction in paw thickness at the end of the experiment. No such effect was observed with ZA or ZA + MTX. *P < 0.05 versus CT group; +P < 0.05 versus ZA group.