The quickest clue is how the pain behaves over the course of a run. Shin splints tend to produce a spread-out ache along the inner edge of the shin that eases as you warm up. A stress fracture usually sits in one spot and gets worse the longer you carry on.
Spread-out pain and pinpoint pain are different animals.
- Shin splints usually cause a spread-out ache along the inner shin that eases as you warm up.
- A stress fracture typically causes pain in one fingertip-sized spot that worsens the longer you run.
- Pain at rest or at night is a sign to see a GP rather than test it with another run.
How shin splints typically behave
Shin splints, known clinically as medial tibial stress syndrome, cause an aching or throbbing pain along the inner border of the shinbone. The sore stretch is usually several centimetres long rather than a single dot, and pressing along it feels tender across a broad area. Many runners notice it in the first few minutes of a session, then feel it fade as the legs loosen up. It often returns afterwards as a dull soreness that hangs around for a while once you stop.
The triggers are rarely mysterious. A jump in mileage, a switch to hillier routes, a new pair of shoes or a return to hard pavements after a break can all load the tissues around the tibia faster than they can adapt. Beginners and people returning after time off are the classic casualties.
Both legs are often affected, though not always equally.
Red flags that point towards a bone problem
A stress fracture is a tiny crack, or an area of overload, within the bone itself, and the pain has a different character. It tends to be localised to a spot you could cover with a fingertip, and pressing on it is sharply tender. Pain also builds during a run instead of easing, and it may start earlier in each session as the days pass.
Pain at rest is another giveaway. An ache at night, or while you are simply walking around the house, is not typical of straightforward shin splints. Swelling or warmth over the painful spot can appear too. Clinicians sometimes use single-leg hopping to provoke the pain, but repeating that at home to check is unwise, because it may aggravate the injury.
Night pain should prompt a call to your GP rather than another test run.
The shin is not the only site. Stress fractures also turn up in the metatarsals of the foot, the heel, the navicular bone on the top of the midfoot and, less commonly, the hip or pelvis, and the pattern is similar: focal pain, worse with impact, slow to settle.
Why the line between them is blurry
Sports medicine increasingly treats bone stress injuries as a spectrum rather than two separate conditions. At the mild end sits irritation of the bone and its surrounding tissue, which is where shin splints belong. Further along comes a bone stress reaction, and at the far end a true fracture. That helps explain why running through shin splints can occasionally lead somewhere worse, and why X-rays often look normal in the early weeks of a stress fracture, with MRI picking up changes sooner.
Certain factors tilt the odds towards bone injury. Low energy availability, where food intake does not keep pace with training, is well recognised (the sports medicine term is RED-S), and it affects men as well as women. A previous stress fracture, low bone density and abrupt increases in training load also feature on the list.
A paperclip bent once is fine. Bend it back and forth repeatedly and it snaps, which is a crude but fair picture of repetitive loading without enough recovery.
What to do before the next run
If your pain is diffuse, eases with warming up and does not wake you at night, backing off is a sensible first move. Self-care guidance for shin splints, including from the NHS, centres on resting from running, using ice packs and choosing supportive footwear. Swapping some runs for cycling, swimming or the cross-trainer keeps fitness ticking over while the shin settles, and calf and hip strengthening is commonly recommended once the pain allows.
A practical rule of thumb: if walking hurts, running is off the table. If everyday movement is pain-free, a gentle run-walk session may be reasonable, stopping at the first sign of sharp or pinpoint pain. Soreness that is no worse the next morning is reassuring. Pain that creeps up session after session is not, and a diary of when it starts and where it sits will help whoever examines you.
Persistent focal pain means seeing a professional, not pushing on.
A GP or sports physiotherapist will ask about your training history, press along the bone and may arrange an MRI if a stress injury is suspected. Confirmed stress fractures usually mean several weeks off impact activity, sometimes with a protective boot or crutches, and the timescale varies with the bone involved. Some sites, such as the neck of the femur, need much stricter management than a shin. None of this replaces personal medical advice, so speak to your GP if you are in any doubt about what is causing your pain.
The much-quoted advice to raise weekly mileage by no more than 10 per cent is a handy guide rather than a law, and research testing it has been mixed. Your sleep, diet, running surface and injury history probably matter more than any neat percentage.