Shin pain when you run: the size of the sore patch decides what it is

Four weeks into a block that is going well, the inside of your shin starts aching in the first ten minutes. It fades once you are warm, so you keep going. A week later it is there for the whole run, and the morning after a long one you can feel it walking to the kitchen.

Almost every runner meets this at some point. Across eight studies covering 3,500 runners, medial tibial stress syndrome had a higher incidence than any other running injury, between 13.6% and 20%¹. The useful question is not what to call it. It is how much of your shin bone is sore.

Run a finger down the bone

Sit down, find the inside edge of your shin bone, and press along it from just below the knee to just above the ankle. You are looking for one thing: how far the soreness spreads.

MTSS is defined by that spread. Pain brought on by exercise along the lower inside border of the tibia, with recognisable pain on pressing over a length of 5 cm or more². It is a diffuse band, not a point.

Spread out

Sore along 5 cm or more of the bone edge

One spot

Sore in a patch you can cover with a fingertip

That distinction matters because a tender patch small enough to cover with a fingertip points towards a bone stress injury, which has its own rules about impact, healing time and imaging. Where a stress fracture sits decides how carefully it has to be handled.

In other words, history and hands find this reliably. There is no test, scan or camera that adds to it.

Fits MTSSTreated as bone stress

Spread

Fits MTSSA band of 5 cm or more along the lower inside edge.

Treated as bone stressOne tender patch, often smaller than a fingertip.

In the run

Fits MTSSWorst in the first ten minutes, often eases as you warm up.

Treated as bone stressArrives earlier in each successive run and keeps building.

Hopping

Fits MTSSUncomfortable, but you can do it.

Treated as bone stressSharp at the same point, and you would rather not repeat it.

At rest

Fits MTSSQuiet once you have been off your feet a while.

Treated as bone stressCan ache at night or when you are doing nothing.

Direction

Fits MTSSSettles over weeks as loading is adjusted.

Treated as bone stressGets worse while you carry on running the same way.

What is happening inside the bone

The old explanation was that muscles pull on the lining of the bone and inflame it. That is where the word periostitis comes from, and it is still in a lot of blog posts.

The bone story fits better. Loading that goes up faster than the bone can keep up with tips the balance so that resorption outpaces the formation of new bone in the tibial cortex, and that pattern shows up on bone scans, MRI, high resolution CT and DXA⁴.

Biopsies taken from the painful area point the same way. Linear microcracks turned up in four of six samples, with almost no sign of a repair reaction around them⁶. Six samples is a small number and the authors say so, but it lines up with the loading picture rather than the inflammation one.

This is not academic. If you believe the problem is inflammation, ice and anti-inflammatories look like treatment. If the problem is a bone that has not been given time to catch up, the dose of running is the treatment.

Do you have to stop running?

Usually not completely, and the threshold is easier than most runners expect.

If walking for about 30 minutes is close to painless and ordinary things like stairs are comfortable, running at a level you can manage is generally reasonable. If walking hurts and stairs hurt, the bone is telling you it needs a quieter few weeks first.

Impact is what the bone finds hard. Most of the rest of your training does not have to stop. Cycling, swimming, pool running and strength work can usually carry on while the shin settles, which keeps the block from unravelling.

What the trials actually found

This is where the evidence is thin, and it is worth knowing why.

Thirteen years later, a review restricted to randomised trials in runners found three trials with 130 runners between them. Arch-support orthoses added to multimodal care reduced pain in the short term against a sham, and the effect did not last. Added exercise was no better than the comparison. No treatment came out clearly ahead⁸.

The one trial that compared realistic options head to head is the most useful thing in the literature:

Shockwave is the one addition with a signal behind it. In a controlled study across two hospitals, 42 athletes on a graded running programme reached the same endpoint in 59.7 days on average when shockwave was added, against 91.6 days without it¹⁰. Patients were not randomised, the treatment cannot be blinded, and the authors asked for a proper trial. It has not been done.

At the other end, pretibial corticosteroid injection has two published cases, both showing skin atrophy and loss of pigment around the injection sites and no benefit¹¹. It is not a treatment for this.

What we do with it

The trials say the graded running programme is doing the work. So the plan is built around it in three overlapping stages, and the strength work is there for reasons the trials were never designed to measure.

First, settle it. Cut impact to the level the shin tolerates, which for most runners means shorter and easier rather than nothing at all, and hold that for one to two weeks.

Second, build capacity underneath. A systematic review of 17 studies, comparing 332 people with MTSS against 694 without, found that lower lean leg girth and reduced plantar flexor endurance were among the characteristics that separated them, along with higher soleus activity during push-off¹². Whether those come before the injury or after it is unresolved.

Third, build back. Run distance before speed, add one variable at a time, and use the next morning as the test rather than how the run felt.

How long it takes

The honest number comes from the control arm of the shockwave study, where the endpoint was running 18 minutes continuously at a fixed intensity without pain. Athletes on a graded running programme alone took 91.6 days on average, with a standard deviation of 43.0¹⁰.

Three months to run 18 minutes hard is slower than most runners want to hear. The spread is the part worth reading. Some people were back inside six weeks and some took twice as long, and 19% of the athletes in the Moen trial stopped because they were not progressing at all⁹.

Why it keeps coming back

MTSS has a habit of returning at the same point in the next training block.

Most of that list is not something you change. The one that is, and the one none of these studies measured, is how the training went up. A previous running injury carrying the strongest odds of the modifiable group tells you something on its own: the pattern that produced the first episode is usually still there.

One more finding from the reliability study is worth carrying around. Of the 34 athletes with MTSS, 11 also had a second lower leg problem at the same time³. A shin that will not settle on a sensible plan is a reason to look again rather than to try harder.

When to get it looked at

The last two are the ones runners skip. Front of shin pain and a history of bone stress injury both change how carefully this is handled, and resolving bony tenderness is the first of five things that should be in place before running is reintroduced after a tibial bone stress injury¹⁴.