This month’s topic is an injury that fortunately is fairly rare. But, like any good bursitis condition, if you do manage to acquire this problem, it can be more than a minor annoyance.
Based on the English translation of this affliction, you might reasonably suppose that the area of difficulty is to be found below the ankles, but the actual location is the upper inside part of your shin. About 1.5 inches below the bottom of your kneecap (patella), directly at high noon on your shin, you will feel a raised bump of bone (the tibial tubercle) where your patellar tendon attaches. About an inch to the inside from that bump is the spot where the tendons of three thigh muscles attach. These muscles – the sartorius, gracilis, and semitendinosus – originate on the pelvis and help to flex, adduct, and extend the hip, respectively. They also assist in flexing the knee. As the three tendons join and attach on the tibia, they splay in a manner that resembles a goose’s foot, so hence the name.
Between these tendons and the bone is a bursal sac which, as we’ve seen before, is a fluid-filled structure designed to act as a buffer to protect the tendons from injury as a result of friction. But, like other bursae, such as in the hip, knee, or shoulder to name a common few, the sac can itself become irritated by too much compression or direct trauma. In the case of the pes anserine bursa, the cause in runners is thought to be related to too much pressure from overuse of some sort. The exact nature of this theory, from a mechanical standpoint, is not well-defined in the literature, other than to blame “hamstring tightness” (the semitendinosus is one of the three hamstring muscles), always a convenient culprit, but one that doesn’t make much sense in this case since it doesn’t explain why the other two muscles play no role.
My own suspicion centers on faulty gait mechanics, specifically overstriding, particularly during the end of the swing phase. As the lower leg is “flung forward” in an attempt to reach farther, the three muscles of the pes anserine group act to rein in what is an excessive amount of knee extension. Then, as the foot makes contact with the ground, the muscles quickly reverse their action to flex the knee in an effort to pull the body forward over the leg. The subsequent extra stress on these muscles, as well as the posteriorally-directed force vector of this muscle action, may be the reason the tendons and bursa become inflamed.
This personal hypothesis was arrived at after noticing that several of the recent cases of this injury have occurred in “power walkers.” As described in an earlier article, a frequent problem with this activity is the tendency to overstride in an attempt to increase walking speed. Runners, while perhaps less likely to overstride than walkers since they can increase speed by increasing the turnover rate, still do try too often to run faster by running longer and so can become susceptible to this type of injury.
The symptoms of pes anserine bursitis are straightforward: pain (stinging, sometimes), tenderness, and occasionally swelling at the site of the tendon attachments. The pain can usually be reproduced by sitting and digging the heel into the ground (isometric knee flexion). Initial treatment is also fairly typical: ice, anti-inflammatory medications, rest if necessary. And, of course, avoid the precipitating factor described above.
Runners should be aware that pes anserine bursitis is often difficult to distinguish from other, more serious injuries, such as meniscus (knee cartilage) tears or upper tibial stress fractures. If your shin pain is severe and unremitting, you feel a clicking sensation in the inside portion of your knee, or have sustained any twisting or direct trauma to the area, you should have it examined by your physician before self-treating the injury.
