Analyses for synovitis of the knee. a Protocol for running without MIA injection. b Synovial sections stained with HE. Whole knee joints were sectioned in the sagittal plane for synovium of infrapatellar fat pad. c Quantification of synovitis evaluated by Krenn’s synovitis scoring system (n = 4). d Protocol for running with MIA injection. e Synovial sections stained with HE. Synovial cell layer is indicated by arrows. f Quantification of synovitis evaluated by Krenn’s synovitis scoring system (n = 4, * p < 0.05 by Steel-Dwass test)