The windlass is that equipment that are used by the mariners on yachts to wind the rope about to help to make it easier to move the sails. Within the foot there is a mechanism that is referred to as the windlass mechanism that gets its name from this equipment used on yachts. There is a ligament like structure beneath the foot known as the plantar fascia which is at one end connected to the underside of the heel bone and at the other end to the big toe. When we are walking and the rearfoot comes off the floor, the foot moves around the big toe or hallux where this ligament is connected, tightening the ligament as it winds about the windlass of the first metatarsal head. This is the windlass mechanism of the foot. It is a vital functionality as the plantar fascia is what supports the arch of the foot, so it ought to function effectively and quickly for normal biomechanics. It is the foots natural arch support mechanism.
There are a variety of conditions involving the windlass mechanism not working adequately. If the windlass does not work, then the arch of the foot will collapse from the lack of support and a variety of disorders may develop as a consequence of that such as hallux valgus and plantar fasciitis. The cause of the windlass not working correctly can be multiple such as the force required to establish it just being way too high, so the body needs to work harder to help make the windlass work. If that effort does make it function, then that is an increased energy expenditure that can be very fatiguing. Clinicians use different design characteristics in foot orthotics to improve the windlass mechanism and to make walking less difficult and more effective. If the windlass can be established easily during walking or running is not going to need so much effort and the foot will naturally support its own arch.