*2.2. 3D Gait Analysis*

In this study, a 3D gait analysis was performed in the Clinical Motion Analysis Laboratory of the University Hospitals Leuven Belgium. The analysis was performed using a multi-segment foot model where reflecting skin-markers were placed according to the Rizzoli foot model marker placement protocol using double-sided tape [16]. This multi-segment foot model calculates the 3D rotation between adjacent segments of the foot and tibia. For reasons of readability, these inter-segment angles will be reported with respect to their corresponding anatomical joints, i.e., the ankle segment (consisting of two joint levels: tibiotalar and subtalar), the Chopart joint, the Lisfranc joint, and the first metatarsophalangeal (MTP 1) joint. Kinematic data were captured with a passive optoelectronic measurement, including ten infrared cameras (T10, 100 Hz, Vicon Motion Systems Ltd., Oxford Metrics, UK). For this study, only the stance phase of gait was considered, which was delineated with initial contact as the start and toe-off as the end. The measurements were taken on the symptomatic side as well as the asymptomatic side. The first measurement was taken as a static recording and was used as a reference position. After this, the dynamic measurements were recorded. The participants were asked to repeatedly walk along a 10 m walkway at a self-selected speed until five representative trials were registered. The walkway was instrumented with a force plate (Advanced Mechanical Technology Inc., 200 Hz, Watertown, MA, USA) in order to determine the gait events such as the initial contact and the toe-off. A plantar pressure plate (Footscan™, dimensions 0.5 m × 0.4 m, 4096 sensors, 2.8 sensors per cm2, RSscan International, Olen, Belgium) was placed on top of the force plate. Plantar pressure and force data were synchronized with a 3D box™ (RSscan International, Olen, Belgium) using an external trigger. These data were sampled at 200 Hz.
