Underpronation is a condition in which the foot does not optimally meet the ground when walking or running. Also called supination, underpronation can be thought of as walking on the outsides of the foot to an individually determined degree, though the intensity of the outward roll may be nearly unnoticeable to the observer at any moment.
Since it is not always obvious to the layman, a simple test of looking at the wear on old walking or running shoes can be used to roughly diagnose underpronation. An underpronator's shoes will have more wear on the outside edge, particularly toward the rear, demonstrating the location of impact when running. It is generally thought that underpronation is not fatalistically linked to foot shape or anatomy, but that it is highly associated with having high arches and being bow-legged.
Pronation is the rolling movement the foot undertakes when cycling through gait. This movement is responsible for distributing forces of impact and shock absorption. Another way to think about it is that pronation controls where and when weight is reaching the ground through the foot. With normal or neutral pronation, the entire foot makes contact with the ground. Underpronators put weight on the outside of the foot, which is too rigid a surface to efficiently absorb shock.
Normal pronation is characterized by initial contact by the outside part of the heel, an inward roll of about 15 percent with complete contact with the ground, and then an even push off the ground from the front of the foot. Underpronation, on the other hand, begins with the outside of the heel making contact with the ground. Instead of rolling inward 15 percent as it would in neutral pronation, the foot instead rolls inward less than 15 percent placing more weight on the outside of the foot. At the end of the gait cycle, the smaller toes must do all the work of pushing off, putting undue strain on those toes.
Underpronators may experience pain in the arch of the foot or the heel, and more rarely lower body pain. Excessive pressure or strain on the foot from underpronation can cause heel spurs if left untreated. Even though damage to the foot from underpronation is unlikely, it is important to wear appropriate shoes both for personal comfort and protection from injury.
There are shoes designed specifically for underpronators, usually featuring extra cushioning, increased shock absorption and added stability. Appropriate shoes are the most commonly recommended method for coping with pain caused by the condition, as well as for preventing damage to the foot. Underpronation rarely requires surgery, and can be considered a relatively benign affliction that only becomes a concern when optimal use of the foot is required.