Why runners get hurt

Running is one of the simplest ways to meet WHO's activity guidelines, and its health benefits are large. Its injuries are largely predictable. The American Academy of Orthopaedic Surgeons notes that stress fractures often follow a sudden increase in activity, and the NHS describes shin splints as pain along the shin bone that commonly affects runners after a change in training. Getting the dose right matters more than any shoe or gadget.

01Shin splints

Shin splints cause pain along the inside edge of the shin bone, often after running on hard surfaces, increasing training quickly, or with worn-out shoes. The NHS advises rest and switching to lower-impact exercise while it settles.

What helps

  • Increase weekly distance gradually and avoid big jumps after time off.
  • Mix in softer surfaces and replace worn running shoes.
  • Strengthen calves and hips with regular exercises.
  • Swap to cycling or swimming for a while if your shins become sore.

02Stress fractures

Stress fractures are small cracks in a bone caused by repeated force, often in the shin, foot or hip in runners. AAOS lists rapid increases in training, inadequate rest, poor nutrition and low bone density as risk factors. Low energy availability, from not eating enough for the training done, can affect bone health in runners of any sex.

What helps

  • Plan rest days and lighter weeks into your training.
  • Eat enough overall, with adequate calcium, vitamin D and protein.
  • Stop running and get assessed if pain is focused on one spot of bone and worsens with running.
  • Women whose periods become irregular or stop with training should talk to a doctor.

03Knee pain and heat illness

Pain around or behind the kneecap is common in runners and usually relates to load and strength around the hip and knee. In races and hot weather, heat exhaustion and heat stroke can occur; the NHS lists confusion and a high temperature as warning signs.

What helps

  • Include strength work for hips, thighs and calves twice a week.
  • Reduce mileage temporarily when knee pain appears, rather than stopping all activity.
  • Acclimatise to heat gradually, run in cooler parts of the day and drink to thirst.
  • Slow down or stop if you feel dizzy, confused or stop sweating in the heat.

Weekly checklist for runners

  • Plan the week's runs with at least one full rest day.
  • Raise weekly distance only gradually.
  • Do two short strength sessions for legs and hips.
  • Check your shoes and track their mileage.
  • Eat a proper meal or snack after hard sessions.
  • Write down any pain, where it is and when it occurs.

When to see a professional

  • Pain focused on one spot of bone that worsens with running or hurts at rest.
  • Pain that makes you limp or alter your stride.
  • Knee swelling, locking or giving way.
  • Missed or irregular periods related to training.

Call emergency services for anyone who collapses during or after a run, or who is confused and very hot. Start CPR if they are not breathing normally.

Where ONU fits

ONU brings your activity, sleep and recovery trends together, so you can compare training weeks with your sleep and recovery and notice when load is outpacing rest. It cannot detect a stress fracture or tell you whether an injury is serious; pain that persists needs a professional.

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Common questions

How much can I increase my running each week?

There is no single safe number, but increases should be gradual, with lighter recovery weeks. Many coaches use small weekly increases and back off every few weeks.

Can I run through shin splints?

Running through worsening pain risks a stress fracture. Reduce or pause running, use lower-impact exercise, and get assessed if pain persists or is focused on one spot.

Do running shoes prevent injuries?

Comfortable, well-fitting shoes help, and worn-out shoes can contribute to pain. Training load matters more than any particular shoe.

Sources and further reading

Educational information drawn from the public-health sources listed on this page. It is not a diagnosis, a treatment plan or a guarantee that you will avoid an illness or injury. ONU does not diagnose, treat or prevent disease. Speak to a qualified professional about anything that concerns you, and follow the rules of your employer, sport or local health service.