The windlass is that device that are used by the mariners on yachts to wind the rope about in order to make it less difficult to move the sails. In the foot there is a mechanism that is referred to as the windlass mechanism that gets its name from this apparatus used on boats. There is a ligament like structure beneath the foot known as the plantar fascia that is at one end attached to the bottom of the heel bone and at the other end to the great toe or hallux. When we are walking and the heel comes off the ground, the foot moves around the great toe where this ligament is connected, tightening the ligament as it winds around the windlass of the first metatarsal bone. This is the windlass mechanism of the foot. It is a important functionality as that ligament is what supports the arch of the foot, therefore it ought to function effectively and efficiently for normal function. It is the foots natural arch support mechanism.

There are a number of conditions involving the windlass mechanism not working properly. In the event the windlass does not work, then the arch of the foot will fail from this lack of support and a variety of conditions may develop as a consequence of that such as bunions and plantar fasciitis. The explanation for the windlass not functioning correctly can be multiple such as the force required to establish it simply being too much, so the body has to work harder to make the windlass work. If that hard work does make it work, then that is a greater energy cost that can be very fatiguing. Clinicians use different design characteristics in foot orthoses to improve the windlass mechanism and to make walking easier and more efficient. If the windlass can be established easily when walking will not require very much energy and the foot can naturally support its own arch.