The windlass is that device that are used by the mariners on yachts to wind the rope about to make it less difficult to move the sails. Within the foot there is a mechanism that is called the windlass mechanism that gets its name from this apparatus used on boats. There is a ligament like structure under the foot known as the plantar fascia that is at one end connected to the bottom of the heel bone and at the other end to the big toe or hallux. When we are walking and the rearfoot comes off the floor, the foot moves around the great toe where this ligament is connected, tightening up the plantar fascia as it winds around the windlass of the first metatarsal head. This is the windlass mechanism of the foot. This is a important function as the plantar fascia is the thing that supports the arch of the foot, therefore it is required to function effectively and quickly for normal function. This is the foots own natural arch support mechanism.

There are a number of disorders linked to this windlass mechanism not working properly. Should the windlass doesn't work, then the arch of the foot will fail from this lack of support and a number of disorders may develop as a result of that such as bunions and plantar fasciitis. The cause of the windlass not functioning properly can be multiple like the force necessary to establish it just being too much, so the body needs to work harder to help make the windlass function. If that hard work can make it function, then that is an increased energy expenditure which can be very fatiguing. Clinicians use several design features in foot orthoses to facilitate the windlass mechanism and also to make walking easier and more efficient. If the windlass can be established easily when walking is not going to need very much energy and the foot can naturally support its own arch.