Flowchart of experimental and computational methods. (A) For each subject, experimental skin-marker data and dual-fluoroscopy data were simultaneously collected. Note, at the foot and ankle, the skin-marker set included markers on the medial and lateral malleoli, calcaneal tuberosity, dorsal aspects of the second and fifth phalanxes, dorsal web space between the fourth and fifth metatarsals, and the dorsal-medial aspect of the first metatarsal head. (B) Using only the skin-marker data, tibiotalar and subtalar joint angles were predicted from inverse kinematic simulations using the 1 DOF and 3 DOF models. (C) Independently, tibiotalar and subtalar joint angles were measured using dual-fluoroscopy. The joint angles predicted from skin-marker data were then compared to those measured using dual-fluoroscopy.