The foot is made up of a complex interaction of bones, ligaments, and muscles. These structures help the foot alternate between being a mobile, flexible adaptor and a stable rigid lever. The foot is broken down into two functional parts, the forefoot and the rearfoot. Overall, the foot functions in three primary ways:
1. Provides a stable platform of support
2. Attenuates impact upon loading
3. Assists in efficient forward propulsion of the body.
When we walk there is a load placed on the foot and the leg. The human foot has a definite, although varying capacity to accept weight before injury results. The amount of weight tolerated before injury occurs varies with the time course of loading and the individual ability to dissipate the loading force.
By modifications of footwear, it is possible to change the load delivered to the body at foot strike and thus decrease injury. Shoewear and orthotics may play an important role in maintaining normal foot function.
The prescription of inserts or orthotics, as well as shoewear or modification of shoewear has three important functions. The first function is to provide protection to the foot and ankle. The second it to help prevent injury by either decreasing the stress on the leg. This is thought to occur through improved impact absorption or attempting to improve the alignment of the leg through compensation for malalingnment. The third possible function is enhancement of performance.
In order for proper function the foot variation must be identified. People tend to have either a flat foot (pes planus) or a high arch foot (pes cavus). Regardless of the variation, the shoe must fit the foot and not vice versa.
Flat feet are generally excessively mobile and the foot has a tendency to move too much. In this case, the ligaments and muscle associated with this area tend to be stressed more than normal. This person tends to have a wide forefoot and a narrow heal which makes it difficult in shoe fitting.
Breakdown is most often seen on the inside of the sole which leaves the foot in an unsupported position. Shoewear should conform to the foot which will give it the support it needs to function properly.
The individual with a cavus or high arch foot will generally have less motion within the joints of the foot and require more room on the top portion of the foot. This foot tends to wear out the outside of the outersole as well as flatten out the outside of the midsole. This foot is often associated with a tight Achilles tendon which results in excessive wear in the forward part of the sole under the ball of the foot.
When choosing a shoe for this foot type, a relatively high heel to relieve stress on the Achilles tendon and a midsole with good shock-absorption to dissipate the forces upon ground contact should be considered. The front of the shoe should be flexible under the ball of the foot. Together this will decrease the chance of injury related to this type of rigid and non adapting foot.
Orthotics are another important adjunct that can be used in order for normal foot function to occur. Orthotics function to keep the foot in a neutral position and decrease or eliminate abnormal compensatory motions and unnecessary stresses. There are three types of orthotics: soft, semirigid, and rigid.
A soft orthotic is pictured here. Its function is to provide cushion, improve shock absorption, decrease shear force, and redistribute pressure. This type of orthotic is indicated for a rigid foot. It provides little support which is not needed in this particular instance.
The most important aspect is to cushion the rigid foot and decrease the force so that injury is prevented.
The next is a semirigid orthotic which is seen here. This orthotic functions to control or balance the malaligned foot as well as provide some flexibility and shock absorption. It has increased compliance and is the most common orthoic prescribed. Those individuals with flat feet are the beneficiaries of this type of orthotic.
Finally, the rigid orthotic serves to control gross unwanted motion. It is not accommodating and offers no shock absorption or cushioning. This type of orthotic is indicated for the neurologic patient that has poor control of their feet.
The effect of proper footwear and orthotic type have on particular foot variations has already been discussed. With flat feet, exercises may also be prescribed as a way to increase the arch. This increase in the arch height would increase its stability and function more optimally. Some exercises are as follows:
1. The individual stands on a towel and with their toes, grabs it.
2. The individual stands holding a TheraBand, turned 90 degrees from the band. Then, rotate
90 degrees while standing on one foot. The muscles in the stance leg are being
strengthened with this exercise.
3. While standing on one leg the individual concentrates on increasing and decreasing the arch
of the foot.
In the flat foot the problem may be corrected with shoe modification, orthotic prescription,
or muscle strengthening. These have all been shown to decrease stress and hence injury to the foot and leg. Flat fleet are more commonly seen than high arch feet.
Persons with high arch feet often have tight heel cords. Therefore, stretching of the calf muscles is important. This can be done as pictured below.
1. Stand facing a wall with your arms straight and palms touching the wall. Put one foot in
front of the other with the leg being stretched behind. Slowly lean forward keeping the
heel of the back leg on the ground. Stop and hold the position when a stretch is felt.
Hold the stretch for 30 seconds and repeat 5 times.
Exercises are not all that helpful in reversing the condition of a rigid foot. Shoe and orthotic management are the keys to dealing with this type of rigid foot.
In cases where individuals lack the knowledge of shoewear modification, orthotic type, and exercises warranted, they should consult a professional who will guide them with the proper education that is needed.