Dr. Ian H. Beiser's Podiatry Page
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Dr. Ian H. Beiser's Podiatry Page
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Office Info |
Normal Anatomy Bones of the foot
Gait There are several important functions the normal foot accomplishes during the act of walking (gait). As you will see, some of these functions appear to be opposites. This means the foot must be able to change significantly at specific periods of the gait cycle. The gait cycle refers to the act of taking a complete step. This is broken down into a stance phase and a swing phase: Stance phase includes the motion between striking the heel on the ground (heel strike) through lifting the big toe off the ground (toe-off). Swing phase goes from toe-off to heel strike when the foot is not bearing any weight. To function normally in gait, the foot must accomplish four major functions. It must be able to adapt to an uneven surface, become a rigid lever for propulsion, translate rotary forces generated by the hip and it must be able to absorb shock. The muscles and tendons work together with the bones, ligaments and joints of the foot to accomplish these goals. If one of those components is not functioning properly, all of the other components may be affected. During heel strike, the foot acts as a shock absorber and begins to pronate. Pronation can best be understood as the motions involved when the foot rolls in and the arch flattens. As this occurs, the foot "unlocks" and becomes loose. It is during this midstance period that the foot is flexible and able to adapt to uneven terrain. After this, the leg begins to externally rotate and foot begins to supinate. Supination is the opposite of pronation and can be thought of as the motion by which the foot goes from being flat to having a higher arch. This is necessary to make the foot more rigid so it can serve as a lever for propulsion (lifting the foot off the ground by rolling over the big toe). People with flexible flat feet may actually have a high arched foot when non-weightbearing but pronate excessively during gait. This means the foot stays "flat" or pronated at a time when it should be supinating and becoming more rigid. This results in instability which may result in bunions, hammertoes, heel pain, arch pain, metatarsalgia and tendonitis. The instability may be controlled with orthotics or sometimes with surgery. People with rigid, high arched feet, cavus feet on the other hand, usually have a diminished ability to absorb shock which may result in conditions such as metatarsalgia, heel pain, knee, back ,hip and lower back pain.( Note that some of the conditions mentioned may be found in both cavus feet and flat feet. However, the mechanism that causes the common conditions usually differs between the high arched foot and the low arched foot) . |
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Ian H. Beiser, D.P.M. Send mail to ibeiser@erols.com with questions or comments about this web site.
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