Stress Fractures in Runners: Warning Signs and Healing Time
A stress fracture is a tiny crack in a bone caused by repeated overload, and it is one injury that running through the pain can make worse. The American Academy of Orthopaedic Surgeons (AAOS) says bone stress injuries are often seen 3 to 4 weeks after starting a new exercise routine or a new sports season, and that they usually take at least 3 weeks to heal. This page summarizes the AAOS OrthoInfo page and the federal Physical Activity Guidelines, as of October 2026. It cannot tell you whether you have one; only an exam and imaging can.
1. What a bone stress injury is
AAOS explains that every time you run or jump, your bones break down a little, and with rest and sleep they build back up to their normal strength or even stronger. That is a normal response to exercise. If bone breaks down faster than the body can rebuild it, a bone stress injury occurs.
AAOS describes a range. In the early stage the bone may swell or bruise, called a bone stress reaction. If you keep exercising through the pain, the pressure can crack or break the bone, which is a stress fracture. The weight-bearing bones of the foot and lower leg are especially vulnerable.
2. What usually triggers one
AAOS says these injuries occur over time when a bone is repeatedly overloaded by a rapid increase in activity. That can mean more days per week, longer runs, or a new high-impact workout. It also notes that people who are not athletes can get one after a sudden jump, for example by walking much more than usual on vacation.
The federal Physical Activity Guidelines make the same point from the injury-prevention side: the risk of injury to bones, muscles and joints is directly related to the gap between a person's usual activity and the new level, which the guidelines call the amount of overload. A small overload with time to adapt lowers the risk.
AAOS also lists risk factors you can change and ones you cannot.
- Modifiable: weak or fatigued muscles, tight muscles and stiff joints, running mechanics, not eating enough for your activity level (it calls this low energy intake), getting under 7 hours of sleep a night and skipping rest days, low vitamin D, worn-out or poorly cushioned shoes, hard surfaces such as concrete, and starting new running or jumping that your body is not used to.
- Not modifiable: biological sex (females are at higher risk, though it is common in both), age (risk increases with age), genetics, foot and leg alignment, and a prior injury.
3. Warning signs
AAOS says the first sign is discomfort in a specific spot along a bone. At first it may show up only at the end of activity or shortly after, and usually goes away with rest. If the injury progresses, you may have discomfort throughout activity, with ordinary walking and daily chores, sometimes with limping. You may also feel aching in bed at night, and swelling or bruising are possible.
This is the main difference from a general muscle ache: the pain is in a small, specific spot on the bone, and it creeps earlier into the run and then into normal life.
4. What to do first
AAOS says to see a doctor or provider as soon as possible if you think you have a bone stress injury, because ignoring the pain leads to worse injury and longer healing. Until the appointment it suggests:
- Rest from activities that cause pain.
- Ice the area for 20 minutes at a time, a few times a day, if there is swelling, never directly on the skin.
- Use over-the-counter anti-inflammatory medicines such as ibuprofen or naproxen if suitable for you, to relieve pain and swelling.
5. How it is diagnosed and treated
AAOS describes an exam for tenderness over the bone, sometimes with hopping on the leg to see if it causes pain, followed by an X-ray. An early injury may look normal on X-ray because bone swelling cannot be seen, so a doctor may begin treatment anyway or order an MRI. A CT scan may be used if a fracture is visible, and a bone density scan if you have factors that weaken bone.
Treatment is aimed at unloading the bone. That means rest from the painful activity, with swimming and cycling named as alternatives that still allow healing. If walking hurts, a hard-sole shoe, boot or crutches may be used. Some slow-healing fractures need surgery.
6. How long recovery takes
AAOS gives at least 3 weeks for bone stress injuries to heal, and up to 3 months or longer for more severe ones. Fractures that were left untreated for weeks or months, or that are in areas with poor blood supply, can take a long time.
7. Key takeaways
- A pain at one spot on a bone that starts late in a run and does not fade should be examined, not run through.
- Sudden jumps in distance, days per week or intensity are the classic trigger, often 3 to 4 weeks after the change.
- Sleep under 7 hours, no rest days, low energy intake and worn shoes are listed risk factors.
- Healing is at least 3 weeks and can reach 3 months or more.
- Swimming and cycling are the alternatives AAOS names while the bone heals.