You bumped up your running distance, switched shoes, or got back into running after time off, and now there's an annoying ache along the front of your shin that gets worse as the session goes on. It's not a bruise, it's not a cramp: it's a pain that builds up gradually, and a lot of people try to push through it until they can't run without limping anymore. That pain has a name — shin splints, or medial tibial stress syndrome — and it's one of the most common injuries among people ramping up running volume, whether starting from zero or coming back after a break. Understanding what causes shin splints and how to treat them properly is the difference between two weeks off and a real fix, versus dragging the problem out for months.
What shin splints actually are
Shin splints happen along the medial side of the tibia, the shin bone, where muscles, tendons, and the periosteum (the membrane covering the bone) get overloaded by repetitive impact. The result is local inflammation that hurts to the touch, bothers you at the start of a run, can ease up during the effort, and comes back afterward — or gets progressively worse until it hurts even while walking. It's not a rare injury: literature reviews show it affects between 4% and 20% of the general population, with much higher prevalence among runners and military recruits in training, precisely the groups that repeatedly ramp up impact volume.
The profile of who's most likely to develop shin splints includes women, people with a higher body mass index, lower prior aerobic conditioning, and a history of smoking, on top of individual biomechanical factors. That doesn't mean men or well-conditioned people are immune — it means the main trigger is always the same: an impact load bigger than what the bone and connective tissue can absorb and remodel in time.
Source: PubMed
Why it shows up: the most common triggers
In practice, shin splints almost always come from the same mistake: increasing volume or intensity faster than the tissue can adapt. Switching to a shoe with less cushioning, moving from treadmill to pavement, adding road running to a routine that was only strength training, or simply getting back into running after weeks off — all of it pushes the shin's bone and muscles into a pace of stimulus they weren't ready to absorb. Add overpronation, weak ankle and calf muscles, and hard running surfaces, and the condition becomes even more likely to show up.