This is accomplished by means of complex mechanical coordination between the highly loaded force-bearing structures of the foot/ankle complex,including the bones, muscles, ligaments, and articular surfaces. Therefore, any injuries or deformities of any of the force-bearing structures will affect the coordination, and thus the normal function of the complex. Since the bony structures provide kinematic links and attachments for the soft tissues, which in turn help maintain the dynamic alignment of the bones, morphological changes, or malalignment of the relevant bones will also affect the normal mechanical environment of the complex, leading to increased risk of injuries [2; 3; 4; 5; 6]. Foot structure problems have been shown to have a prevalence of 46% to 80% in clinical practice [7; 8]. Maintaining a normal morphology and bony alignment is essential for the prevention of relevant injuries. Assessment of the sole morphology provides a clinically useful measure of the condition of the bony alignment and force-bearing structures. Several parameters quantifying the sole morphology have been proposed and used in the literature and clinical practice, such as foot length (FL) [9], foot width (FW) [10], arch height (AH), normalized arch height (NAH), arch index (AI) [11], Staheli's arch index (SAI) [12], Chippaux-Smirak index (CSI) [13], hallux valgus angle (HVA) [14], minimal distance between hallux and other toes, great toe height, and instep height, etc. [15; 16]. Among these parameters, those related to the medial longitudinal arch have received much research attention because the medial longitudinal arch is one of the most important features of the foot structure, relating to the absorption of ground forces and propulsion. The height of the medial longitudinal arch provides a direct measure of the foot morphology and function, and has been used to classify foot morphology into various types of normal-arched, low-arched, and high-arched feet. Abnormal arch height will compromise the load transmission and weight-bearing capabilities of the tarsal bones, increasing the risk of injuries of the ankle complex [17; 18]. While the sole surface geometry and the medial arch height are three-dimensional in nature, the relevant measurement has been limited to two-dimensional or non-weight-bearing conditions. This is primarily because 3D measurement of the sole morphology under weight-bearing conditions is technically challenging, if not impossible [19]. Most existing clinical assessments of the medial arch morphology and arch height are based on 2D footprint or pressure distributions, which are easy and convenient to perform, but cannot measure directly the vertical dimensions, such as arch height [20]. In addition, the accuracy is limited as the arch morphology is 3D in nature, and the assessment is often affected by the experience of therapists or physicians (i.e., raters) [21; 22; 23]. Several attempts to predict 3D arch morphological parameters using a 2D footprint or planer pressure distribution have been reported in the literature. For example, a multivariate (5-6 variables) model based on plantar pressure parameters has been shown to predict only about 60% of the variability of the static arch height [24; 25]. Other studies found no or moderate correlation between sub-areas of the plantar pressure area of the foot and common foot parameters, such as foot posture index, calcaneal pitch, metatarsal angle, and alocalcaneal angle [26]. The results of these studies suggest that features from the static or dynamic planar pressure distribution failed to predict the three-dimensional (3D) foot morphological parameters, especially the arch height. With the advance of 3D scanning technology, it is possible to use 3D scanners to scan the shape of the foot [20; 27; 28; 29; 30; 31]. Three major types of 3D scanning methods have been developed and used for body shape reconstruction, namely laser sensors [27; 28; 30], depth sensors [31; 32], and photogrammetry [20; 29; 33].