the runner's guide to shin pain

“Shin splints” is one of those broad terms that many people (doctors included) use to describe a very wide range of conditions. In other words, if someone says “shin splints” what they actually mean can be several different things.
 
Going “by the book,” shins splints is synonymous with “medial tibial stress syndrome” which is basically irritation at the connection between muscle (usually the posterior tibialis) and the tibia (shin bone). Tends to be a repetitive strain condition, but can have underlying causes in mechanics, strength, mobility or training load; or in the case of bone injuries there can be nutrition causes as well.
 
Occasionally, the irritation might be on the muscle itself without any irritation to the bone, in which case it would be some form of posterior tibialis strain or tendinopathy of the posterior tibialis tendon, if closer to the ankle.
 
As for bone injuries, we can have a stress reaction or a stress fracture. The difference is these is basically one of degree. Think of a stress reaction as the beginnings of a stress fracture. Whereas a stress reaction might dissipate within days if given time to heal, a full blown stress fracture can know you out of a solid couple of months. The hallmark sign will be pain/tenderness in a specific spot, whereas many other shin conditions will display pain along a longer segment.
 
On the outside of the shin on the more “meaty” muscle side, we can have anterior tibial tendinopathy or tibialis anterior strain. You may also hear the term “compartment syndrome” which gets tossed around quite liberally referring to pain on the outside of the shin, but full blown compartment syndrome is a true medical emergency, where you’ll experience numbness, loss of circulation and changes to skin texture. The gold standard to diagnose compartment syndrome is to measure the pressure inside the compartment. 
 
Sometimes, shin pain isn’t shin pain at all, but is instead nerve pain from the lower back. You could also experience nerve-like symptoms from irritation at the outside of the knee. But in these scenarios, the symptoms are less likely to be associated with movements or direct stress to the lower leg.
 
High ankle sprain is also slim possibility, but unless you’ve had an acute incident of twisting your ankle or lower leg, it’s safe to rule this one out.
 
Ultimately, these diagnoses are simply descriptive labels. Most important is identifying how and why these are happening, but understanding that many different conditions can exist under the realm of “shin splints” is a good way to start!