Quantifying the role of the windlass mechanism in increasing foot stiffness

The windlass mechanism of the human foot is a well known anatomical feature that causes the height of the medial longitudinal arch (MLA) to rise in response to toe dorsiflexion under constant load.¶ It is interpreted as a stiffening mechanism which is hypothesized to work by increasing the moment arm of the plantar fascia about the midfoot, thereby increasing its overall stiffness.¶ However, no direct load-displacement measurements of the foot exist at different levels of windlass engagement. ¶ Here we perform three-point bending tests on a cadaveric foot at different levels of toe dorsiflexion.¶ The resulting load-displacement curves indicate a small change in average stiffness while the true stiffness given by the slope of the curve changes by an even smaller amount.¶ We hypothesize that engaging the windlass likely unloads the foot causing the MLA to rise, while leaving the true stiffness of the foot relatively constant.