The tell is that you can point to it. A stress fracture is tender at one spot on the bone, an inch across, that hurts when you press it; ache spread across the whole inside of your shin is usually shin splints instead. And the pain marches: it starts mid-run and clears by morning, then creeps earlier, lingers longer, and finally aches at rest.

Bone rebuilds on a three-to-four-month cycle, chewing out damaged patches and refilling them. Ramp training faster than that and for a few weeks the chew-out runs ahead of the refill, so the bone gets weaker before it gets stronger ¹. That is why the danger window is two to six weeks into a new load: the session you got hurt on found the bone at the bottom of its dip.

In women the fracture is often the loud symptom of a quiet problem. Women break roughly four times as often as men, usually because eating less than the training burns switches off the hormones that protect bone ². Missing periods, slow-healing niggles, and flat energy are the same picture: the female athlete triad, or RED-S ³. Fix the bone but leave the fuelling and you refracture, at about five times baseline ⁴.

Two or three of these together: stop running and get imaged.

Recovery is staged. Get the leg walking pain-free, hold fitness with cross-training, and fix the fuelling in parallel. Then a run-walk progression on alternating days, stopping at any return of focal pain. Low-grade breaks at low-risk sites clear in six to eight weeks; high-grade ones take three to six months and a small share need a screw ⁷. In women who restore their intake, periods often return within six to twelve months ⁸. The bone you keep in your twenties is bone you still have at sixty.