The Sub-Talar Joint - A Real Neighborhood Dive

You've heard me mention the sub-talar joint many times, and probably think I go to bars with weird names, but seriously - I do. I just have a preference for this particular joint, where all the tunes on the juke box are variations on the Twist. (Boy, am I dating myself. Which is a good thing, because no one else will - bah-da-boom.)

Actually, this is the first in a series on basic biomechanics. The intent of this series is to help other clubbies better understand their own particular feet better, and to make it easier to understand the strange foreign language of doctors, which is nearly as indecipherable as their handwriting (did you know that the last course a doctor takes before graduating is medical penmanship? If the professor can actually read your test answers, you flunk.) So today's lesson, cats and kitties, is the subtalar joint. Hop up on a bar stool, place your order with the bartender, and let's get started.


First of, without the subtalar joint, we would all walk like a cartoon figure, throwing one leg forward, planting it fully, then swinging the other forward. We most likely would not have evolved the ability to run, which means the saber tooth would have gotten more of us, as would the mountain lions, tigers, bears, tax collectors, etc., which by extension means we wouldn't be a very crowded planet, and probably no internet, and thus, no blog. And that would be a bummer, wouldn't it? Because without a subtalar joint, the leg cannot rotate over the foot while the foot is planted fully on the ground. Go ahead - try it. Try to twist your foot against the ground while your leg is directly over it, then keep doing that every step. It's OK, I'll wait.....

So? How was that? Pretty difficult, and I'm sure, very tiring. And if you did that all day, your knees and hips would be killing you tomorrow, trust me on that. The subtalar joint is the only joint in the body that operates in all three "cardinal planes." What, you are asking, as if I could hear you, is a cardinal plane? No, its not the one used by that team from St. Louis. A cardinal plane refers to the three planes we move in, and consist of the frontal plane (or coronal plane), the sagittal plane, and the transverse (or horizontal) plane. Here is an excellent and easy to understand explanation. And here is a video showing all three planes, with other motion-related terms for easy understanding. Most joint operate within only two planes, because there is no need for rotational motion to be transferred. While the hip and the shoulder joints move in three planes, they don't of themselves transfer motion. The subtalar joint allows the rotational motion of the leg as it passes over the ground to take place without making the knee and ankle joints provide the same motion, which they are not designed to do - the knee is a hinge joint, and the ankle, as well, and neither is capable of moving through all three planes of motion.

There are many views of the subtalar joint that can be found on the Web, but here is one simple one:

The talus is the bone over which sits the two bones of the lower leg - the tibia, and the fibula. The talus, in turn, sits on, or more properly, articulates with, the calcaneus, what we often refer to as the heel bone. It is this articulation, between talus and calcaneus, that we call the subtalar joint. It is the shapes of the "articular surfaces," or, the intersection of the two bones, that determines the motion that can occur between them, more properly, the motion of that joint. The talus and the calcaneus, in turn, articulate with other bones, and through that motion transfer motion from the ankle, to the mid-foot. You might liken the subtalar joint to a universal joint, that translates vertical motion to horizontal.

But with talipes equino-varus, the talus is dis-articulated from the ankle "mortise," and also from the calcaneus. A major part of the re-forming of the post-natal club foot is designed to get the talus and the calcaneus back under the ankle and in proper articular positions. Hence all the stretching, casting, and bracing, not to mention the surgical interventions. Yes, there are other joint-alignment issues, as well, but this - the subtalar and ankle alignments, are the most critical.

But we post-clubbies know, if not by word, at least by function, that we have less subtalar motion, and more subtalar pain, than non-clubbies. Most of that pain occurs in the space between the talus and the calcaneus. Because of the shapes of the joint surfaces of both bones, there is a sort of cave between those two bones, properly termed a "sinus," the sinus tarsi, to be exact. It is in the sinus tarsi where most of our degenerative joint changes are going on. You can test this quite easily. Grab your foot (any foot- your choice) and stretch it back toward it's original clubbed position. You should feel immediate reduction of the pain. This is because you are, in effect, opening the sinus tarsi, thus relieving the compression of the joint, which is what you are doing all the time you are on your feet. So finding ways to open that joint up are the key to reducing pain in that area. Unfortunately, the solution of fusion of the subtalar, while it will in fact (temporarily) reduce that pain, it will simply force the ankle and knee joints to produce motion they are not designed for.

So the key is to find ways, such as massage and stretches, properly designed orthotics, and proper fitting footwear, to keep that joint even a little more opened up, instead of staying at its end of range of motion continuously. Wikipedia has an excellent explanation of the concept of range of motion here.

If you want even more on the subtalar joint, its quite easy to find way too much on the Web. I recommend shaken rather than stirred, but that's just me. Next time, we'll go down the street to the mid-tarsal joint.  They have lots of micro-brews. tell 'em Lenny sent ya.