Conway McLean, DPM, Journal columnist

Although we may not think about it (and most people rarely do unless they have pain), our feet do wonderful things for us, transporting us through the world with each and every step.

Our ability to ambulate, the act of walking, is a complex event, entailing hundreds of different motions and activities, stresses and strains. Abnormalities with this process, even subtle variations from the norm, can eventually lead to pains and problems not obviously linked to minute changes in foot motion.

The ankle joint is a prototypical hinge articulation, up and down, with minimal variations. In contrast, the most important joint in the foot is the subtalar joint (the STJ), which is immediately below the ankle, and is composed of the talus bone and the heel bone.

This is not a simple structure, being composed of three different joint surfaces. The motion of the STJ moves the foot in three different directions relative to the leg which, taken as whole, constitute pronation and supination.

These are the two primary motions of this essential body part, and both are necessary for gait and stance (i.e. walking and standing). In order for the foot to adapt to the uneven surfaces found in nature, the STJ must be able to pronate, in which the arch rolls down.

This movement is also critical to absorbing the impact of each and every step. Supination is the opposite motion, whereby the arch gets higher. This allows the foot to “lock up,” or stiffen, for the pushing off needed at the end of each step.

Because most modern humans walk on perfectly flat surfaces most of the time, the same direction and type of subtalar joint motion occurs with nearly every single step. With ten thousand steps a day, over hundreds of days a year, this repetitive movement will often stress some structure.

Or, if the motion is in the wrong direction, some component of the lower extremity or spine becomes stressed on a repetitive basis, leading too often to the degenerative changes of chronic inflammation. Time is a critical element in this discussion since these problems are a consequence of repetition.

A common rule in nature is that too much of anything is a bad thing. And so it is with subtalar joint motion. There isn’t enough space here to list all the consequences of Hyperpronation Syndrome. It is recognized as the most common cause of hammertoes. Because the alignment of the arch is “off kilter,” the delicate balance of structures running out to the toes is thrown off, pulling the toes away from “normal” alignment and into deformity.

One of the most common orthopedic conditions seen in modern society is plantar fasciitis, aka heel pain. This is generally considered the prototypical cause of pain from the bottom of the heel. When the arch ligament is stressed or pulled on too much, such as when the arch rolls down too much, it becomes inflamed and painful. This problem can be nearly disabling and is often recurrent, making weight bearing on the extremity difficult.

A frequently seen deformity of the lower extremity is a bunion, in which the first metatarsal bone gradually drifts away from the other metatarsals. The big toe doesn’t follow it out but, instead, the great toe is pulled by its tendons causing it to lean slowly over towards the lesser toes. This abnormal alignment is more common, and more severe, in feet that pronate excessively, which tends to unlock the foot. Reducing hyperpronation with foot orthotics explains why some type of arch support relieves symptoms for so many bunion sufferers.

Numerous Americans have obtained relief of back pain by using some kind supportive device for the arch. How can a foot support relieve back pain? By altering the positioning of the talus bone, which is the bottom half of the ankle joint. This bone is locked in on both sides by the two leg bones. Thus, the talus can’t turn towards the middle of the body, a motion which is part of pronation, without the lower leg turning. This results in extra rotation of the upper leg and that alters the position of the pelvis, tending to stress the lower spine. Preventing excess rotation of the talus bone will reduce leg rotation, sparing the lower back from chronic, low-grade stress.

We have only touched upon the many dangerous consequences of excessive pronation. From chronic, recurrent Achilles tendonitis to inner ankle (Posterior Tibial) tendonitis, numerous soft tissues and bones can become diseased from the effects of overpronating. Because the foot tends to swing outward (relative to the leg) as a consequence of pronation, excess shoe pressure may be exerted on the outer surface of the foot. Or the subtalar joint itself becomes chronically inflamed and painful from the excessive motion of the joint.

There are many ways of minimizing excessive pathologic foot motion. Knowing when one would benefit from such efforts is another story. Stretching out the Achilles tendon can be a beneficial approach when the Achilles is tight, which tends to pull the foot into pronation. Shoes are part of the discussion, and if the hyperpronation is mild, a more stable shoe may suffice. But producing a more optimal foundation for the skeletal system via an arch support may be needed.

A prescription device, termed foot orthotics, should be prescribed through a detailed, in-depth analysis of foot shape, positioning, and biomechanical function. When accurately performed, these often eliminate the pathologic motion and so relieve what are often chronic, lasting problems. When not prescribed through this exhaustive process, foot orthotics may simply hurt.

Too many Americans live with chronic aches and pains, many of which have a biomechanical origin. Hyperpronation is the most frequent root of these symptoms, all resulting from abnormal body mechanics. How many knee replacements could have been prevented by addressing the biomechanical origin of the knee stressors leading to cartilage degeneration? If you suffer from some similar aches and pains, maybe your problem is rooted in your foot, leg and spine mechanics. So get evaluated and get supported: hyperpronation may be the culprit!

EDITORS NOTE: Dr. Conway McLean is a podiatric physician now practicing foot and ankle medicine in the Upper Peninsula, having assumed the practice of Dr. Ken Tabor. McLean has lectured internationally on surgery and wound care, and is board certified in both, with a sub-specialty in foot orthotic therapy. Dr. McLean welcomes questions, comments and suggestions at drcmclean@penmed.com.