Gait analysis by CatWalk in an arthritic rat. Time course of the print area (A) and the duration of stance phase measured as the fraction of total step duration (B) of all four paws in a nine-week-old female pristane-treated rat walking across the CatWalk walkway. Front paws are shown with filled symbols, hind paws with open symbols. The left side is shown with circles, the right side with squares. Gait parameters are depicted in black, arthritis score in red. (C) Picture of CatWalk footprints on Day 24 after injection of 150 μl pristane oil. Prints of the left paws of the rat are shown in red, and prints of the right paws are shown in blue. Prints of front paws are depicted in lighter colour, whereas prints of the hind paws are darker. (D) Picture of the CatWalk gait diagram 24 days after pristane-injection. Indicated are the paw-floor contacts for each of the paws over time. The length of each bar represents the duration of the stance phase for that particular paw. The space between bars represents the duration of the swing phase. Decreases in print area as well as in the stance phase in the arthritic paws are observed (arrows).