Marker-based CTX of the foot bones of a pig while it’s walking. Small metal beads were surgically implanted in some of the foot bones and in the hoof. Only those bones with markers are shown. (The middle bone isn’t shown because it’s not marked for this study.) A 3-D model from CT scanning was made of the foot. High-speed cinefluoroscopic video of walking was collected, and the x-ray video was used to align the markers in the CT model to produce an accurate (±1 mm) reconstruction of bone position over time.