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Bone stress injuries occur over time when the bone is repetitively overloaded with a rapid increase in physical activity. This can be from:

• Increasing the frequency of activity — such as exercising more days per week.
• An increase in duration or intensity of an activity — such as running longer distances or starting a high-impact workout.

Bone stress injuries are often seen 3 to 4 weeks after starting a new exercise routine or a new sports season.

Even for non-athletes, a sudden increase in activity can cause a bone stress injury. For example, if you do not do much walking on a day-to-day basis and end up walking more than you are used to on vacation, an injury may occur.

A stress fracture is an overuse injury. It occurs when muscles become fatigued and are unable to absorb added shock. Eventually, the fatigued muscle transfers the overload of stress to the bone causing a tiny crack called a stress fracture.

Other factors can put you at increased risk of developing a bone stress injury. Modifiable risk factors are things that you can change, while non-modifiable risk factors cannot be controlled. These risk factors can be extrinsic (coming from outside the body) or intrinsic (characteristics within an individual).

Non-modifiable risk factors include:

• Biological sex: Females are at higher risk than males, but bone stress injury is common in both.
• Race: White people have lower bone density and weaker bone structure than other races.
• Age: Bone stress injury risk increases with age.
• Genetics: You may have a higher risk of a bone stress injury depending on how your genes are expressed to control bone health.
• Alignment: Different degrees of foot arch height, foot length, leg length, and knee alignment can increase risk.
• Prior injury: An injury significantly increases your chances of having another injury in the future.

Modifiable risk factors:

• Strength: Weak muscle cannot absorb as much force, so the force is then put through the bone.
• Fatigue: Tired muscles and a tired body are not able to absorb forces which are then transferred to bones.
• Flexibility: Tight muscles and stiff joints will not absorb as much force, sending the force through the bone.
• Biomechanics: The way you run and jump can change the force transmitted from the ground through the body.
• Low energy intake (relative energy deficiency in sport, known as REDS): Not taking in enough fuel for your level of exercise will increase the risk of developing a bone injury. Learn more: Sports Nutrition
• Recovery: Those who get less than 7 hours of sleep each night and do not take rest days (days where you do not exercise) are at higher risk for stress injury.
• Nutrition: Low levels of Vitamin D may lead to poor bone healing.
• Footwear: Worn-out, poorly cushioned shoes may increase risk.
• Training surface: Hard surfaces without spring (like concrete) will increase force through the body
• Volume and intensity of training (this is known as training load): Starting new running or jumping activities that your body is not used to will increase risk.

Anyone can get a bone stress injury, but this injury is commonly seen in:

• Active individuals who participate in running and jumping sports or recreational activity.
• People with more risk factors, even if they have lower levels of activity.
• Female athletes in cross country, gymnastics, and outdoor track; these athletes have the highest rates of stress fractures.
• People in the military.

People who take certain long-term medications or have conditions (like osteoporosis) that cause a decrease in bone strength, , which can make you more likely to experience a stress fracture — even during normal everyday activities. This type of stress fracture is known as a bone insufficiency stress fracture.

The weight-bearing bones of the foot and lower leg are especially vulnerable to stress fractures. 

When a bone stress injury begins, you may notice discomfort in a specific spot along your bone. At first, discomfort may occur only at the end of physical activity and for a short time after activity. This pain usually goes away with rest.

If a bone stress injury becomes more severe:

• You may have discomfort throughout physical activity, with regular walking, and during your activities of daily living (household chores, shopping, etc.). Sometimes, the pain may cause you to limp.
• You may notice aching while lying in bed at night.
• Swelling and bruising are possible.

See your doctor or provider as soon as possible if you think that you have a bone stress injury. Ignoring the pain will lead to worse injury, and you may take longer to heal.

Until your appointment with your doctor or provider:

• Rest from activities that cause pain.
• Ice the area if swelling is present. Use cold packs for 20 minutes at a time a few times a day. Do not apply ice directly on your skin.
• Over the counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, can help relieve pain and reduce swelling.

Physical Examination

Bone stress injuries need to be evaluated by a doctor or healthcare provider if you have frequent pain with sports activity. This is especially true if you have multiple risk factors.

On exam, a doctor or healthcare provider will look for bone tenderness at the spot where you feel pain when you exercise. If the site of pain involves the leg, your doctor or healthcare provider may have you hop on your leg to see if this causes pain.

Imaging Tests

To fully evaluate the bone, your doctor or healthcare provider will order an X-ray.

• If your injury is more severe, the X-ray may show signs of the bone injury healing or a crack in the bone.
• If you are in the early stages of injury, the X-ray may look normal, as bone swelling cannot be seen on X-ray.

If your exam suggests a bone stress injury, your doctor or healthcare provider may choose to start treatment and see how you respond.

• In some cases, they may order an MRI, which can show bone swelling.
• If a stress fracture is present on X-ray, they may order a CT scan to look at the break in the bone more clearly.
• If you have one or more factors that put you at increased risk of weaker bones, or you have an injury that occurred with light activity, they may order a bone density scan (DEXA). This is a different type of imaging that looks at the strength of the bones throughout your body. If you have low bone mineral density, you may need a nutrition evaluation or to consider medications to help strengthen your bones. Learn more: Osteoporosis Prevention and Treatment

Treatment will vary depending on the location of the stress fracture and how serious the fracture is.

A bone stress injury is caused by bone overload. Treatment is aimed at unloading the bone to allow it to heal. These injuries are, therefore, typically treated with:

• Rest from activities that cause pain. Swimming and cycling are good alternative activities that will still allow your injury to heal.
• If you have pain when walking, a hard-sole shoe, boot, or crutches to take more pressure off the bone and allow it to heal.
• Surgery. Bones that take a long time to heal might require surgery to heal properly. In most cases, this involves supporting the bones by inserting a type of internal fixation, such as pins, screws, plates, or rods. Most of the time the hardware does not need to be removed after the bone has healed. Occasionally, your surgeon may advise removal of the hardware; this is typically a quick outpatient procedure, meaning you go home the same day as your procedure.

Bone stress injuries usually take at least 3 weeks to heal, but if they are more severe, they can take up to 3 months or longer.

Longstanding stress fractures (meaning the fracture happened weeks or months ago and has not yet been treated) or fractures in high-risk areas with poor blood supply can take a long time to heal. Although it can be hard to rest, resuming activities too early can make the injury worse and delay healing.

Pain is used as a guide to determine how your injury is healing. If you have a fracture, your doctor may order repeat X-rays or a CT scan to assess healing.

When a doctor has cleared you to return to sports activities,  your return must be slow and gradual so your bone can adjust to the increase in load. This may mean alternating days of activity with days of rest, or adding in more cross training with biking and swimming. It may take many weeks to slowly increase the frequency, duration, and intensity of exercise to get back to your full activity level.