The contribution of transverse ligaments to the longitudinal bending stiffness of the foot

Foot stiffness plays an important role in its mechanical function. The medial longitudinal arch (MLA) is thought to be the primary determinant of foot stiffness. Cadaveric studies bisecting the plantar fascia that maintains the MLA found that stiffness decreased by 25% [1,2]. Mathematical and physical models [3] and foot stiffness measurements in human subjects [4] suggest that the transverse arch plays a crucial role in determining foot stiffness by coupling sagittal plane bending with transverse stretching. Therefore, bisecting structures that restrict transverse splay should decrease foot stiffness. Using a three-point bending test on a cadaveric human foot, we found that the effect of bisecting the deep and superficial transverse metatarsal ligaments and tissues connecting the metatarsals on foot stiffness was as great as the effect of bisecting the plantar fascia. This suggests that the role of the transverse arch in determining foot stiffness is as important as the MLA.