In this study, we revealed that only 50% of the rats completed 30 km of running. 0.1 mg MIA induced cartilage matrix depletion at the tibial cartilage and 15 km of running further exacerbated, even though 15 km running did not affect the cartilage in the PBS injected knee. Synovitis caused by MIA improved with time whether or not rats were forced to run.