In my previous post I talked about the nomenclature surrounding shin splints. In this post I'll actually get into the nitty gritty of what shin splints are. I'll focus mainly on the most common pathologies, but if you recall from my first post, shin splints can be an all encompassing term for lower leg pain. If you have questions about anything not mentioned in this post then please comment below and I'll answer any and all questions to the best of my ability.
Medial Tibial Stress Syndrome
As I've mention in Part 1, a commonly used synonym for shin splints is Medial Tibial Stress Syndrome (MTSS). As the name suggest, it's classified as a stress along the medial (and distal) third of the tibia.
There are a number of causes of MTSS, one of which is believed to be periostitis of the tibia in response to tibial strain under load. Periostitis is inflammation of the periosteum, which is the membrane that lines outer surface of the bone, and, consequently, which which muscles will connect. Other causes may include remodelling of the perisoteum, and tendinopathy - all of which can be considered a consequence of overuse.
The muscles that are mostly involved are the tibialis posterior, tibialis anterior and the soleus. This explains why pain from MTSS is typically felt along the inferior medial border of the tibia, this is where the belly of the three muscles turn into the more fibrotic tendon and therefor the area of the most stress. As I've mentioned previously, MTSS is typically a consequence of overuse, hence why the areas of greatest pull (tendons) will be the area of greatest pain.
There are also underlying biomechanical reasons why MTSS may be present, and one of the most common being overpronation of the foot. Overpronation places added stress on the tibialis posterior and the soleus because pronation of the foot stretches the soleus and tibialis posterior. This puts them in a less then optimal alignment during running activity. Another somewhat common predisposing factor for MTSS is a narrow tibial diaphyseal width - or in layterms - a teeny tiny middle bit of the shaft of the shin. Unfornately shin width can't really be altered, but overpronation can be. I'll get into this in the treatment section later.
Another cause of shin splints is simple tendinopathy. This can expalin why some people experience pain in areas other than that of MTSS. Personally, when I get pain I feel it somewhat laterally, just below the knee. To be a little more precise, I get pain at the origin of the tibialis anterior. This is one of the other more typical areas that people describe when they say they have shin splints. This is also around the area of the origin of extensor digitorum longus. Besides the commonly felt area above, tendinitis may also appear along the anterior surface of the shin where other muscles originate or in the belly of the muscles above.
Depending on the health professional you talk too there may be mother causes of shin splints, or they may classified shin splints differently depending on their personal definition. To me the above two pathologies best describe the pain of shin splints when ruling out stress fractures and compartment syndrome. inflammation of the interosseus membrane may also be a reported cause of shin splints. There are other factors that are considered to be causes or predisposing factors for shin splints. I'll simply list them.
Overtraining on uphill/uneven terrain
Short bursts of sprinting activity
The take home message from all of this is that shin splints can most often fall into the overuse category of injuries if you consider that compartment syndrome and stress fractures are their own separate pathologies.
In my next post I'll take about prevention and treatment of shin splints.
What do you guys think:
Would you consider shin splints to be predominantly an overuse injury?
Have you experienced shin splints? Tell me about it.
Can you think of any other causes for shin splints?