The foot is an amazingly complex structure, with a great variety of tasks, many of which are essential for longevity and quality of life. How it performs these functions, such as weight bearing, locomotion and balance, is a topic of some debate, and continued research. Contrary to popular opinion, there is a tremendous amount of information lacking from our understanding of foot and leg function. Certainly, we know quite a lot, but the specifics have yet to be fleshed out, to be thoroughly appreciated.

Let’s examine, for a moment, how gait, the act of walking, occurs. You put one foot in front of the other, and there you go! You are on your way. That is roughly how much thought we put into it, although, as you may have surmised, it is not that simple. Especially when evaluated in detail.

And how does the foot adapt to standing on a slanted surface? It does so ably, without our having to think about it. What about running? How does the human body propel itself so quickly, without falling over, tripping, or going down in a heap?

To answer these questions, at least partially, we have to talk about the quarterback of the foot, the joint most intimately responsible for much of foot and leg function. That is my appellation for the sub-talar joint (the S-T joint), which is the joint below the ankle.

Whereas the ankle joint allows the foot to go up and down, and that’s about it, this is not the case with the sub-talar joint, the foot’s quarterback, which is in control of how well and how far, how comfortably, your feet can carry you.

Ever heard the terms supination and pronation? Walk into any running shoe store in America and you’ll be certain to hear these terms bandied about. These are the two basic motions the foot goes through with movement of the sub-talar joint. With each and every step, the sub-talar joint is “going through the motions.”

But these are critically important motions, with pronation allowing the dissipation of the energy of impact, occurring every time your foot comes down. Every time you take a step, one and a half times body weight is placed on the musculoskeletal system.

If not properly absorbed, this force can cause degenerative changes to many structures of the body. Thus, pronation, occurring at the sub-talar joint, allows the body to channel these forces produced by each step.

Right about now, you are probably wondering about supination, as well you should be. When the S-T joint supinates, the many joints of the foot “lock up,” allowing the foot to become a rigid lever. Active, forceful gait requires an appropriate degree of supination. This creates an excellent spring-board for the next step, propelling the body forward. Now you’re going places!

Predictably, things don’t always work the way they are supposed to. Genetics is a funny thing, producing all sorts of variations on human anatomy. Add in abnormalities during development, and you have many opportunities for alterations in the workings of the bone-muscle-tendon system. One of the most common is an excessively pronated foot, where the arch is lowered, especially late in the contact stage of gait when the foot is on the ground. The S-T joint should be moving into a supinated position at this point.

The consequences of this lowered arch are numerous and range from the gradual formation of bent toes (hammertoes) to knee arthritis. Tendonitis of the muscle-tendon unit that helps to support the arch is another. How about low back pain? Yes sir, that also is a common consequence. Heel pain, aka plantar fasciitis, is an extremely frequent complication of this failure of the sub-talar joint to move in the right direction, and at the right time.

To understand how the sub-talar joint can cause problems higher up, like the knee or back, one only has to examine the anatomy of the foot. One of the two bones comprising the S-T joint, the talus, is the bottom component of the ankle joint. This bone is locked into the lower leg bones in the ankle mortice (actually a building term), so that when there is abnormally high amounts of pronation, the lower leg is rotated inward at a time in gait it should not be. And in nature, too much of anything is a bad thing. This rotated position of the lower leg places tremendous stress on the knee and pelvis over time. Consequently, the spine is also ultimately affected.

Any doctor trained in lower extremity “biomechanics” is experienced in recognizing this situation, that of excessive, prolonged pronation. Because it is so common, it is called pronation syndrome and can often be identified by simple, chair-side exam. When the correct, weight-bearing technique is used, radiographs, aka x-rays, are essential in quantifying the severity of this deviation from the norm, as well as in identifying some of the structural consequences (like degenerative joint disease, more commonly called osteoarthritis!). A gait exam, critical for an accurate diagnosis of many lower extremity conditions, should also be performed if you are experiencing pain due to improper mechanics. Fluoroscopy, a wonderful technology, is also helpful since it allows a physician to look at a joint move. (In essence, it is real-time x-ray imaging, as a movie could be compared to a still camera image.)

Do you need your sub-talar joint examined? Not necessarily, but if you have chronic foot pain, some way, somehow, your sub-talar joint is probably involved. The same can be said for many conditions occurring above the foot. Various treatments for improving the function of a poorly aligned S-T joint are available, although surgery is rarely needed. Which options are best is a complex topic and I’m certain you, dear reader, sincerely want it covered in the appropriate detail. Rather than gloss over this fascinating subject, I will return to it soon. You are just going to have to wait!

Not that treating this kind of pathology effectively is easy to do. It often goes under-appreciated or unevaluated, but it may be extremely important in determining why you have pain. Although few are experienced in body mechanics, it is critical to address its function to find the cause of many foot, ankle, leg, hip and back problems. So, remember, ignoring your sub-talar joint is fraught with danger. Do so at your own risk. If you have chronic pain in one of these areas, you may have a quarterback controversy!

Editor’s note: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula, with an upcoming move of his Marquette office to the downtown area. McLean has lectured internationally on wound care and surgery, being double board certified in surgery, and also in wound care. He has a sub-specialty in foot-ankle orthotics. Dr. McLean welcomes questions or comments atdrcmclean@outlook.com.