Increased frequency and intensity of certain activities can cause stress fractures. These are small cracks in a bone that can become complete fractures without treatment.

For instance, people can get stress fractures from doing too much too soon with a new exercise training program.

In a person with a stress fracture, the natural bone remodeling cycle is interrupted, leading to bone weakness at the site of the fracture. People with stress fractures may feel a dull, throbbing pain at the point of injury that goes away with rest.

Read on to learn about stress fracture symptoms, causes, diagnosis, treatment, healing time, and more.

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A stress fracture is a tiny crack in a bone due to repetitive trauma. Sudden increases in exercise intensity or duration frequently cause them.

Overuse means the muscles become so fatigued that they can no longer absorb shock properly. This shock transfers to the bone, which can cause a fracture.

Although stress fractures can affect nearly any bone in the body, they commonly occur in the:

  • feet
  • legs
  • hip
  • spine

A person with a stress fracture will usually experience a gradual buildup of pain at the site of the injured bone. This may occur over a few weeks or months.

Putting weight on the injured bone typically worsens the pain, while resting improves it. However, as the injury progresses, a person may experience pain during rest and upon waking.

Other symptoms may include tenderness to the touch and swelling.

Suddenly increasing training without enough recovery time can interrupt bone remodeling, an essential bodily process, and lead to stress fractures.

Bone remodeling is the continual process of removing and replacing old and damaged bone with new and healthy tissue. This cycle allows the body to adapt to accommodate different loads placed on the skeleton during a person’s daily activities.

If a bone cannot adapt quickly enough to an increase in load, it can interfere with bone remodeling and leave an area of weakness in the bone, known as “bone stress.” Then, if a person maintains this stress level, it can cause a stress fracture.

Stress fractures are most likely to affect a person’s weight-bearing bones — for instance, the bones in their shin and foot.

In particular, people who do long-term, intensive sports or military training experience stress fractures.

Inherent characteristics that place a person at higher risk of stress fractures include:

  • being in poor physical health
  • being female
  • having a hormonal disorder
  • having a menstrual disorder
  • having low bone density
  • having reduced muscle mass
  • having one shorter leg

External risk factors include:

  • high impact sports, such as running or jumping
  • a sharp increase in physical activity
  • an irregular or angled running surface
  • inadequate footwear
  • wearing running shoes older than 6 months
  • vitamin D and calcium deficiency
  • smoking

A doctor will talk with a person about their pain and may ask about physical activity and sports. They will check the areas for tenderness and swelling and may ask a person to do the “one leg hop test.” People with tibial stress fractures typically cannot repeatedly hop without pain.

The doctor might also try the “fulcrum test” for femoral shaft stress fractures. This involves the doctor putting their arm under the person’s thigh while applying pressure to the knee. A person will experience pain at the site of the injury.

After performing in-office tests, a doctor may also order imaging tests, including:

  • X-rays
  • CT scans
  • bone scintigraphy, which uses a small amount of radioactive material to assess the severity of bone conditions, such as stress fractures
  • MRI scans

Treatment will depend on the location of the stress fracture and how well it is likely to respond to rehabilitation. However, stress fracture treatment usually involves rest and taking pressure off the injured bone.

A person with a high risk stress fracture — one that has a higher chance of incomplete healing — might decide to proceed with conservative management, such as using crutches. However, a person may need surgery if a fracture is at risk of not healing properly, although this is uncommon.

For lower-risk stress fractures, conservative management may involve two phases.

During phase one, doctors recommend pain relief and a reduction in weight bearing. They also recommend changes to activities, including stopping the activity that caused the injury.

During phase two, a person gradually returns to typical activity over several weeks with the support of physical therapy. This can only begin after the person has had a period of pain-free rest.

Stress fractures usually take 6–8 weeks to heal, but more serious fractures may take longer. The earlier a person receives treatment, the sooner they are likely to heal and recover.

With adequate rest and rehabilitation, most sports people with stress fractures return to sporting activities with typical function and minimal pain.

The American Academy of Orthopedic Surgeons recommends the following stress fracture prevention strategies:

  • eating a balanced diet rich in calcium and vitamin D
  • using running shoes with a softer sole inside and a stiffer sole outside to maximize their ability to absorb shock
  • building up slowly with new activities, gradually increasing the time, speed, and distance
  • varying activities to prevent overstressing one part of the body — for instance, alternating high impact running with lower-impact swimming
  • including strength training in workouts, such as body weight exercises or free weights
  • stopping the activity if the pain or swelling returns and resting for a few days to see if the pain resolves

A sudden increase in training load or intensity can place excess strain on the bones, leading to stress fractures. This can cause tenderness, pain, and swelling.

Appropriate pain relief, rest, and activity modifications usually help a person recover from a stress fracture, but more serious cases may need surgery.