A small crack in the bone that results from repetitive force (rather than trauma), stress fractures are common in athletes, like runners. The injuries also often occur in older people whose bones aren't as strong or have been weakened by conditions like osteoporosis, which reduce bone density.
Stress fractures most commonly occur in weight-bearing bones, namely those in our feet and lower legs. That includes the long bones in the middle of our feet, called the metatarsals.
A classic example of this is what's referred to as a march fracture. "Military recruits get it because they have a rapid increase in their training," explains Dr. Joseph Bosco, vice chair of the department of orthopedic surgery at NYU Langone Health and vice president of the American Academy of Orthopaedic Surgeons. "Or we see it when people are training for the marathon. They could get fractures of their foot or hip as they do that. So a rapid increase in their activity level -- that's one risk factor."
What Causes Stress Fractures?
To prevent stress fractures, it's important understand the factors that increase a person's risk for sustaining one in the first place. Those include:
-- Repetitive activity -- especially a sudden increase in weight-bearing exercise.
-- Age, as bone density and bone quality tends to decrease over time.
-- A history of stress fractures.
-- Gender -- women are more prone to osteoporosis, thus increasing fracture risk.
-- Irregular or infrequent menstruation, or skipping periods.
-- A syndrome called relative energy deficiency in sport, or RED-S.
-- A poor diet that's deficient in calcium, vitamin D and other nutrients.
-- Taking steroid medications, or corticosteroids, on an ongoing basis.
Smoking decreases blood supply to bones and nicotine slows production of cells called osteoblasts, which make bone. Similarly, drinking excessively can compromise bone quality and weaken bones. And taking corticoid steroids, which may be prescribed for inflammatory conditions like arthritis, over a long period can also reduce bone density.
RED-S describes several issues that increase fracture risk. RED-S is marked by having poor bone health. Those with the condition may have osteoporosis or osteopenia. The latter is a precursor to osteoporosis; with osteopenia, the bones are weaker than normal, but the deficit isn't as severe as it is with osteoporosis.
Referred to formerly as female athlete triad, RED-S tends to occur in some women who are exercising a lot and who develop health issues that increase fracture risk. Those issues include disordered eating or low energy availability (not getting enough from foods eaten). Ample calories and nutrients like calcium and vitamin D are necessary to promote bone health.
Women with RED-S typically have infrequent periods (oligomenorrhea) or the absence of menstrual periods (amenorrhoea). Research suggests these menstrual irregularities can lead to a deficiency in hormones like estrogen that slow the resorption, or breakdown of bone over time, which can weaken bones.
The theory is that those with this syndrome "just don't have enough energy reserve to carry on the normal bodily functions," says Dr. Marc Harwood, chief of non-operative sports medicine at Rothman Orthopaedic Institute and an associate professor of family and community medicine at Sidney Kimmel Medical College at Thomas Jefferson University in Philadelphia. This can interrupt the menstrual cycle, and disordered eating can result from not consuming enough food to keep up with energy demands. Taken together, the syndrome can increase one's risk for a stress fracture.
Reducing Your Risk
By getting a better handle on what leads to stress fractures, it's possible to reduce your risk. Here are some tips experts suggest to do just that:
Cross-Train to Break Up Repetitive Workouts
Running lots of miles? Do something else for a change of pace.
"We advocate cross-training," Bosco says. In the midst of marathon training, for example, he suggests taking a day or two off from running and doing something else like riding a bike or swimming.
Vary your activity to strengthen your body and improve your fitness with weight-bearing and aerobic exercise, while taking breaks from repetitive exercise.
Make Sure You're Getting the Nutrition You Need
Yes, you absolutely should meet daily requirements for calcium and vitamin D to sustain strong bones, experts stress. For most adults, this includes getting 1,000 milligrams of calcium. For women over 50, 1,200 mg of calcium are recommended.
In regards to vitamin D, recommendations vary considerably. Experts frequently suggest taking in at least 800 international units, or IU, daily; but some say far more is warranted.
It's optimal to get nutrients from diet, namely whole foods, which provide a diversity of vitamins and minerals. However, it's best to talk with a doctor and a registered dietitian to determine to what's possible and if supplementation is necessary.
Nor is calcium and vitamin D all that matters. Instead, a well-balanced, overall nutrient-rich diet is important to reduce fracture risk. "Nutrition is really, really important for maintaining bone health," emphasizes Sarah Van Riet, a registered dietitian at UW Health in Madison, Wisconsin.
Although you might think your bones aren't changing like other parts of your body, that's not the case at all. "Bones are constantly remodeling -- so they're not stagnant, they're not always the same," Van Riet says. And you don't get the calories and nutrients you need that can lead decreased bone density and bone loss over time.
While calcium and vitamin D are thought to play the most significant role in bone health, other nutrients that contribute include phosphorus, magnesium, zinc, copper, vitamin C and iron, Van Riet notes. For example, zinc helps with bone healing, magnesium plays a role in improving bone density and vitamin C is involved in the formation of collagen, an integral protein found in bone (as well as other places in the body like cartilage).
In regards to a diet that's supportive of healthy bones, it's hard to go wrong with one that's well-proven to support overall well-being. In particular, an eating pattern similar to the Mediterranean diet, which includes lots of plant-based whole foods, a good amount of protein, whole grains and some dairy, is something Van Riet suggests. "The Mediterranean diet has been shown over and over to be a really healthy eating pattern to follow, and that's what I would steer people towards."
Be careful not to crowd out nutritious food with highly processed, less nutrient-rich, sugary or fried fare. Additionally, if you're trying to shed extra pounds, make sure you're not over-restricting calories. Getting the energy you need from the food you eat can also help protect against fractures.
[SEE: Eating for Your Bones.]
Do Everything You Can to Prevent Osteoporosis
Diet and lifestyle overall play a big role in reducing osteoporosis risk. So make sure you:
-- Eat a well-balanced diet with ample calcium and vitamin D.
-- Eat enough. Don't skimp on calories you need to meet energy demands.
-- Engage in regular activities that put weight on your bones, like walking and jogging.
-- Don't smoke.
-- Don't drink in excess -- no more than one drink a day for women or two for men.
Good sources of calcium include not only dairy, which is often fortified with vitamin D as well, but dark, leafy greens like spinach and kale, almonds, beans and salmon. Salmon is also a top source of vitamin D along with other fish like trout, swordfish and tuna. And non-dairy milks like almond milk, as well as pork and eggs are other good sources of vitamin D.
Take Time to Heal
Because stress fractures often aren't as obvious as broken bones that result from trauma -- like a car crash or collision on the playing field -- they can sometimes be overlooked. And continued use of that bone can make the injury worse.
So it's important to heal any pain, particularly that which is pinpointed to a specific area -- like within the foot -- and which hurts when you touch the area. You might also notice swelling in that area and feel more pain when you return to certain activities, like running, when the bone is used.
It's critical to seek medical attention to be evaluated. That can involve getting an X-ray, and in some cases an MRI. This imaging that can provide a closer look at what's causing your pain and help in diagnosing a stress fracture.
If you're diagnosed with a stress fracture, take care to follow doctor's orders. That could range from wearing a walking boot to avoiding putting pressure on the fractured bone for a time, to surgery in more severe cases. Since having a past fracture can increase risk for another in the future, it's important to pull back from repetitive activities until you've properly healed.
If you've sustained multiple stress fractures, it's worth taking a closer look at the bone stock -- or how strong your bone is, Harwood says. Imaging may be used to more closely evaluate bone. In some instances, a DEXA or DXA scan (for dual-energy X-ray absorptiometry) may be ordered to measure bone mineral density to evaluate for osteoporosis.
Ultimately, when it comes to protecting your bones, "it's really about listening to your body," Harwood says. In working closely with your doctor, make sure to stay active without overdoing it to minimize the risk of a future stress fracture.