Synovitis caused by MIA was observed 7 days after injection; however, synovitis was reduced after 3 weeks with or without 15 km of strenuous running. Additionally, only 15 km of running did not induce synovitis. This means that the strenuous running did not exacerbate and influence synovitis in this model. However, we cannot exclude qualitative or quantitative effects of running that might not be detected by Krenn's score (e.g. changes in cytokine expression, macrophage subtypes, etc.)