Medial tibial stress syndrome is related to tibial stress reactions and stress fractures, which you can read about here
For an in-depth discussion of returning to running following a bone stress injury like medial tibial stress syndrome, see this article
Medial tibial stress syndrome (MTSS), or shin splints, is perhaps the best-known running injury to the average citizen. Aching or throbbing shins is an ailment that many new runners and many athletes in all sorts of impact-related sports, like volleyball, basketball, and sprinting, deal with on a regular basis. Unlike some running injuries, which appear to be non-discriminatory—both Joe Jogger and Ryan Hall suffer from plantar fasciitis, for example—medial tibial stress syndrome seems to be an issue encountered more often by new or seasonal athletes (though not exclusively). The reasons for this tie in closely with its root causes, which we’ll get to in a moment. Shin splints also have a complicated and fascinating relationship with tibial stress fractures, which we will also get to later on in the article. If you’ve read my Injury Series post on tibial stress fractures, you might see some familiar material. But first, as usual, we need a bit of anatomy.
Anatomy and terminology
The tibia is your “shinbone,” the long, straight bone that forms the front of your leg. The tibia carries a significant portion of the impact that goes up your leg when you hit the ground, and it also serves as an attachment point for the muscles that control your foot and ankle, all the way from the relatively small ones like the flexor digitorum longus muscle, which flexes your little toes, to the calf muscles, which are the engine below the knee for forward movement. The medial edge of the tibia runs up the inside of your leg and borders your calf muscles. The “stress” part of medial tibial stress syndrome just means that the condition is demonstrably associated with weight-bearing stress from exercise. Other more exotic names for medial tibial stress syndrome have cropped up, like “exercise-related lower leg pain,” but at this point, medial tibial stress syndrome or MTSS seems to be the predominant and most useful term. In this article, I’ll use these terms interchangeably with “shin splints,” the less-descriptive and colloquial term for this injury, but keep in mind that the medically-correct term is medial tibial stress syndrome.
The most obvious symptom of MTSS is, of course, shin pain. The pain usually presents as an aching, burning, or throbbing feeling along the inside edge of the shinbone, usually dispersed over several inches along the shin. The shin (or often, both shins) gets progressively more painful throughout the duration of a run or workout. Early cases of shin splints might be nothing more than a bothersome ache near the end of a long run, but can progress to the point where even short jogs cause pain. There may also be some tenderness along the medial edge of the tibia. One review study recommends that medial tibial stress syndrome be defined as pain which extends for at least 2 inches along the middle to bottom-third of the shin, which is aggravated by weight-bearing and subsides with rest.1 Cases of shin pain which is localized to a very small area should be examined by a doctor to rule out a stress fracture. X-rays are insufficiently accurate to rule out a tibial stress fracture, so your doctor should use a bone scan or, preferably, an MRI, to diagnose your injury.