Take an Aspirin, and Call Sally in the Morning

In our last encounter, faithful reader, we spoke glowingly about the Subtalar Joint. So today, we will talk about what isn't really there. I mean, of course, the empty space inside the subtalar joint, better known as - wait for it - the sinus tarsi. Sounds like some high priest of the Mongolian steppes, doesn't it? You can almost hear the thundering echo off the distant mountains when you say it, right? No? Oh, well, let's talk about it, anyway, OK?

The sinus tarsi is defined by the space created between the calcaneus and talus.

When the subtalar joint loses cartilage, and compensates toward a maximally pronated position, which is fairly common in post-club feet, it is the sinus tarsi that becomes one of the primary locations for chronic pain. Usually, though not always, properly casted and constructed foot orthoses can provide a few degrees of relief by preventing the subtalar joint from reaching its end of range of motion with every step. Essentially, end of range of motion is where a given joint cannot move further in a particular direction, or cardinal body plane. An example is when you try to over-extend your elbow joint - eventually, you cannot make it go any further, unless you are trying to break it. In which case, it's probably going to hurt. Very badly.

Sometimes, the sinus tarsi can become so inflamed it is essentially "hot" all the time. The pain can be very debilitating. There are options, though each has only a limited amount of effectiveness. Orthotics, as mentioned. Sometimes, an injection of cortisone can break the inflammatory cycle long enough that the joint has time to settle down, but its somewhat hit-or-miss - sometimes it works, sometimes for only a short period, and sometimes it doesn't work at all. It seems somewhat dependent on the degree of inflammation, and the actual amount of range of motion available for the specific joint. The more motion available, the better the results.

I tend to go for the chain-reaction approach: soaks and massage, plenty of stretching of the joint in an inversion direction. Then the cortisone, and then newly casted orthotics. This last is because if you can capture the foot by casting it when it is at its most relaxed, it can be positioned better for the resultant orthotics made on that cast.

Cuboid Syndrome

The cuboid is the bone that abuts the lateral aspect of the calcaneus, and is so named because, well, its essentially a cube. It has the least amount of contouring of any other joint surface in the body, and this makes it very easy to become "subluxed." This is simply a fancy word for dislocated. In fact, the cuboid can be subluxed for a long time before anyone even knows it is the source of any pain. There are a few podiatrists, and maybe even fewer chiropractors, who have the skill to do proper adjustments to move the cuboid back into congruency. The interesting thing about these kinds of adjustments are that, when done properly, the relief is nearly instantaneous. You need to look around to find anyone whose properly trained, as foot adjustments are not in the standard curriculum of either disciplines - they are acquired through specialized training and certification.

The thing that causes the cuboid to sublux, of course, is chronic over-pronation, as this, in effect, torques the calcaneal facet of the calcaneal-cuboid joint away from the facet of the cuboid. This causes the ligaments, over time, to stretch sufficiently that the cuboid is no longer held in the proper configuration against the calcaneus. And when this subluxation occurs, it places even greater pressure on the sinus tarsi. The result? Big ouch.

An excellent description of Cuboid Syndrome can be found here.

So, next time you are hangin' with the clubbies at the Subtalar Joint, give a shout out to that old shaman, Sinus Tarsi. Just don't be downwind when he has to blow his nose.