Durrant M, et al. - Investigators ought to establish a common instantaneous center of rotation for the metatarsophalangeal and metatarso-sesamoid joints to understand the functionality and consequent structural failures like hallux abducto valgus and hallux rigidus. They developed a general plane model which represented the most elementary form of the joint. They also established its center of rotation with a range of tangential and normal lines. Mext to it, they also prepared simplified tibial sesamoid and fibular plane models which, when consolidated, allowed the development of a spherical model with 3 distinct contact points. The model was adjusted to correctly determine the center of rotation and one distinctive sagittal plane geometric and functional characteristic of each groove, based on the morphometrics of each sesamoid groove and a more distally positioned tibial sesamoid.