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Runner Tips

What is a stress fracture? Here's what every runner needs to know

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Forget side stitches and runner's knee — research shows that almost a third of all running injuries can be categorized as stress fractures. So, what's up with all the stress? Here's what every runner needs to know about stress fractures and how to sidestep them for safer, pain-free runs.

What is a stress fracture? Basically, a stress fracture is a tiny crack or severe bruise in a bone, according to the American Academy of Orthopaedic Surgeons (AAOS). And while these little splinters can theoretically happen anywhere in the body, they're most likely to strike runners in their lower legs, feet, and ankles, per the Mayo Clinic. After all, stress fractures happen when your bones take too much strain — but not quite enough to completely break the bone. And your legs and feet carry the bulk of your weight (and impact!) during running.

Stress fracture causes and prevention

When you think of a bone fracture, you probably think of taking a hard fall, right? Well, stress fractures happen even if you stay on both feet — and that's how most do happen. That's because stress fractures happen gradually over time with repeated stress, the AAOS notes.

Hence, why they're called overuse injuries. In runners, the vast majority of stress fractures come from doing too much, and often, too much, too soon.

Your bone is living tissue, it's in a constant state of turnover: Old cells die and slough off, and new ones are born. With excessive exercise — and not enough rest — the breakdown of old bone outpaces the creation of new bone. As a result, bones become weaker and more prone to stress fractures, according to the AAOS.

Two women running on a pavement path

It's important to note here though, that stressing your bones isn't all bad. It's just a bit of a Goldilocks scenario. See, just like running can strengthen your muscles, it can strengthen your bones. Weight-bearing and, in people with healthy bones, high-impact exercise like running, can signal the bone to create more and more new cells, increasing your bone mineral density and bone strength, according to research from the University of Missouri.

But when you suddenly put a lot more or different stress on your bones, it's a jolt, and not always one that your bones can handle without sporting some small fractures along the way. The most common jolt: A quick ramp-up in weekly mileage. For instance, if you go from running 1 mile to 3 miles per week, the difference might sound small in theory, but it's a 300% jump. And most experts recommend not increasing weekly mileage by more than 10% each week.

Meanwhile, things like suddenly switching running surfaces can be enough to trigger a stress fracture. For instance, if you're used to running on soft dirt trails (or a springy treadmill) and switch to pounding pavement, that means a lot more impact with each step.

While that's not to say the high-impact nature of running on super-hard surfaces is bad, but making a quick switch is risky. Ease into anything that involves more thumping during your runs.

Symptoms of a stress fracture

Keeping an eye out for stress-fracture symptoms is important for runners, especially when switching up your running routine or building toward longer, harder runs. If you experience any of these symptoms, visit your doctor to learn what's going on — and the best way for you to feel better:

  • Pain that's isolated to a specific spot along a bone (most common in the feet, ankles, and lower legs)
  • Pain that worsens during weight-bearing activities and eases during rest
  • Swelling, tenderness, and possible bruising around the pain site
man running with water and mountains in the background

Treatment for stress fractures

Fortunately, healing up doesn't have to be that difficult. Resting — taking a load off your bones — is non-negotiable in stress fracture treatment. That means refraining from running and limiting your walking as much as possible, notes the AAOS. When you need to walk somewhere, make sure to wear super-cushy, supportive shoes. It'll help lessen the impact your fracture takes with every step.

And how long does it take to recover? According to the AAOS, most stress fractures take six to eight weeks to fully heal. And more severe cases can take longer.

So, no, unfortunately, this isn't going to be an overnight fix. But stick with it. Pushing through the pain can worsen the little crack into a full-blown break — and those come with a much longer recovery timeline.

The best way to speed up your recovery? Visit your doctor. By evaluating the pain site, taking images like X-rays, and talking through your exercise routine, lifestyle, nutrition, and overall well-being, a health care professional will be able to identify any nutritional deficiencies (ahem, vitamin D) or health conditions (like osteoporosis) that may have contributed to your stress fracture. After all, once this fracture heals up, you don't want another one sidelining you.

With this new knowledge about one of the most common running injuries, you're better equipped to tread carefully and ensure healthy, happy runs well into the future.

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Written By
K. Aleisha Fetters

Certified Strength and Conditioning Specialist

Headshot of Aleisha Fetters

I'm a quirky (aka nerdy) strength coach with a passion for science and sweat. I love to help people meet their body goals, but it's their mental and emotional gains that make me do a happy dance. My flirtation with running includes two half marathons and, someday, I will run 26.2.