Stress fractures are tiny cracks in a bone. They're caused by repetitive force, often from overuse — such as repeatedly jumping up and down or running long distances. Stress fractures can also arise from normal use of a bone that's weakened by a condition such as osteoporosis. Stress fractures are most common in the weight-bearing bones of the lower leg and foot. Track and field athletes and military recruits who carry heavy packs over long distances are particularly susceptible, but anyone can have a stress fracture. If you start a new exercise program, for example, you might develop stress fractures if you do too much too soon.
At first, you might barely notice the pain associated with a stress fracture, but it tends to worsen with time. The tenderness usually originates from a specific spot and decreases during rest. You might have swelling around the painful area.
Stress fractures often result from increasing the amount or intensity of an activity too quickly. Bone adapts gradually to increased loads through remodeling, a normal process that speeds up when the load on the bone increases. During remodeling, bone tissue is destroyed (resorption), then rebuilt. Bones subjected to unaccustomed force without enough time for recovery resorb cells faster than your body can replace them, which makes you more susceptible to stress fractures.
Some stress fractures don't heal properly, which can cause chronic pain. If underlying causes are not addressed, you may be at higher risk of additional stress fractures.
Doctors can sometimes diagnose a stress fracture from a medical history and a physical exam, but imaging tests are often needed.
X-rays. Stress fractures often aren't apparent on regular X-rays taken shortly after your pain begins. It can take several weeks — and sometimes longer than a month — for evidence of stress fractures to show on X-rays.
Bone scan. A few hours before a bone scan, you'll receive a small dose of radioactive material through an intravenous line. The radioactive substance accumulates most in areas where bones are being repaired — showing up on the scan image as a bright white spot. However, many types of bone problems look alike on bone scans, so the test isn't specific for stress fractures.
Magnetic resonance imaging (MRI). An MRI uses radio waves and a strong magnetic field to produce detailed images of your internal structures. An MRI usually can visualize stress fractures within the first week of injury, and can visualize lower-grade stress injuries (stress reactions) before an x-ray shows changes. This type of test is also better able to distinguish between stress fractures and soft tissue injuries.
To reduce the bone's weight-bearing load until healing occurs, you might need to wear a walking boot or brace or use crutches. Although unusual, surgery is sometimes necessary to ensure complete healing of some types of stress fractures, especially those that occur in areas with a poor blood supply. Surgery also might be an option to facilitate healing for elite athletes who desire a more rapid return to sport or laborers whose work involves the stress fracture site.