From alignment to helical tension: A biotensegrity-based multiscale conceptual framework for foot and ankle mechanics.

Foot and ankle biomechanics have traditionally been described using alignment-based and joint-centric models. While these approaches have contributed substantially to clinical and biomechanical understanding, they may not fully explain the dynamic, three-dimensional, and force-driven nature of foot function. This conceptual review synthesizes published biomechanical, kinematic, and plantar pressure studies together with biotensegrity principles to propose an integrative framework for foot and ankle mechanics. Based on this concept, we propose a multiscale double-helix model of the foot and ankle. In this framework, two interrelated helical tension pathways coordinate force transmission, energy storage, and functional rigidity through twisting and untwisting during gait. Pronation and supination are thereby reinterpreted as global manifestations of helical deformation within a distributed tension network rather than isolated joint motions. The model further suggests that the apparent rigidity of the foot during push-off may emerge from organized tension dynamics across multiple scales. This framework may also provide a new way to interpret common deformities and treatment strategies by focusing on tension modulation rather than static alignment alone. The proposed model offers a conceptual basis for future investigation of foot and ankle mechanics from a dynamic and integrative perspective.