Inevitably, if you are around runners long enough the question of orthotics will come up in discussion. Recently on regional e- mail lists there was a lively debate about orthotics - who needs them, what is the best type, and where to get them. This article will try to answer these questions to aid each runner in making the proper choice.

Orthotics, more properly called functional foot orthoses, are custom-made shoe inserts that are intended to adjust an abnormal or irregular walking pattern by altering the angles at which the foot strikes the ground. Anything other than custom-made devices are more properly called shoe insoles. To understand how orthotics work and why someone would need them, we must first review a normal gait pattern. About 25 percent of the population has a &normal foot.& This type of foot strikes the ground on the outside of the heel. After heel strike the foot will pronate or roll inward about four degrees - this amount of pronation is normal and is necessary in order to absorb shock.

Problems occur for the 50 percent of the population that over- pronate. In other words, after heel strike their feet pronate or roll inward more than four degrees. Over-pronation involves a loss of stability of the feet. Individuals who over-pronate put excessive strain on the arch of the foot that can lead to inflammation of the plantar fascia. The plantar fascia is a fibrous band that runs from the heel through the arch into the soft tissues in the ball of the foot. Straining this fibrous band can lead to plantar fasciitis and heel pain or spurs.

Approximately 25 percent of people under-pronate. This type of foot rolls in less than four degrees when the heel strikes the ground. This is a very stable foot, often a foot with a high arch, but it is a poor shock-absorbing foot. This lack of shock absorption can lead to knee and hip problems.

So where do orthotics fit into this picture? Well, the motion of the foot pronating or its opposite motion called supinating is a tri-planar motion that takes place in the sub-talar joint of the foot. The sub-talar joint is the joint between the talus and the calcaneus (or heel bone). The talus is the foot bone that sits between the tibia and fibula of the leg to make up the ankle joint and sits on top of the calcaneus. If pronation describes the foot rolling in after the heel hits the ground, the opposite motion or supination describes the foot rolling outward after heel strike. An ankle sprain is an extreme example of supination. Orthotics are used to control sub-talar joint motion and thus control pronation and supination. To correctly make an orthotic, one makes an impression fo the foot with the sub-talar joint in the neutral position - not supinated or pronated. The orthotic device is designed in such a way that when the heel strikes the ground it allows for four degrees of pronation to occur.

What type of orthotics to use depends on what you are trying to accomplish for the foot. For the over-pronator, generally a more rigid type of orthotic is necessary since you are trying to limit the amount of rolling in that occurs. Most commonly a hard plastic like polypropylene is used. If a thinner, lighter orthotic is desired with the strength of polypropylene, a graphite composite material can be used. To gain shock absorption and increase comfort, the rigid type of orthotics can be covered with a material such as Spenco or Sorbothane.

Softer types of orthotics are indicated for under-pronators, to fill the arch and provide increased shock absorption. Materials such as cork, plastizote, aliplast, or leather can be used.

The decision to use an orthotic or an over-the-counter insole relates to the degree of the problem. For mild over-pronators, an over the counter insole with a good motion control running shoe may be enough correction to avoid injury. But for more than mild over-pronation, generally an orthotic - a custom device is required. Orthotics are expensive; they will generally run between $300 and $500 and may or may not be covered by insurance. They will, however, last anywhere from two to five years depending on the type and your activity level, which may work out as a small price to pay to keep running injury-free.

The important point to remember when considering orthotics is that they should be customized for your feet and running, and made by someone well-trained in foot biomechanics. Orthotics are meant to be comfortable and they should make your feet feel better - not worse. While there is a lot of science that goes into deciding upon and making an orthotic, there is some art as well and sometimes adjustments are necessary. The final orthotic product should be something you would not think of going on a run without, not an expensive dust collector in the back of your closet.

Dr. James R. Christina is a podiatrist practicing in Rockville, MD. He is board certified by the American Board of Podiatric Surgery and a member of the American Academy of Podiatric Sports Medicine. He is the past president of the Maryland Podiatric Medical Association and has been a member of the Montgomery County Road Runners Club since 1991.