Stress fractures are small cracks in the bone caused by repetitive stresses or overuse, such as the repetitive impact on the bones of the lower leg and foot during running and jumping activities. This injury commonly occurs in the weight bearing bones of the feet, upper and lower legs, and hip area.
Any athlete may encounter this injury but those with lower bone density due to genetic, metabolic or dietary issues are more susceptible. Women may be more susceptible to stress fractures as well due to irregular or absent menstrual cycles, eating disorders or osteoporosis.
Recovery time usually ranges from six to ten weeks.
What is a stress fracture?
When bones are subjected to stresses they adapt, just as muscles do, to become stronger. To increase in strength they must rob calcium from one area to build another. This weakens that area and new, and repetitive, stresses on that weakened area can cause a crack. This fracture is a result of the bone's inability to handle the stress over time.
Weakened bones, due to old injuries or other conditions, are much more susceptible to stress fractures because they are unable to handle the new stresses applied to them. Athletes with compromised bone density must be very careful when increasing their work load.
Increases in intensity, duration or frequency can lead to stress fractures due to the process of repair and rebuilding being interrupted. The bones need adequate rest time to rebuild and restructure. If unable to repair, the bone will weaken and become susceptible to fracture. Treatment must be initiated as soon as possible to prevent further damage and a more severe fracture.
What sports and activities are most vulnerable?
While stress fractures can occur in any sport, they are most common in high impact sports of a repetitive nature. Sports such as basketball, track and field, dance, gymnastics and tennis are all examples of sports with a high frequency of stress fractures.
Athletes in any sport can fall victim to stress fractures if their form, posture or technique is incorrect or conditions change without a chance to adapt. Changing playing surfaces or using worn shoes, with poor support, can increase the risk as well. Increasing training loads too quickly or changing intensity without a period of time to adapt will make athletes more susceptible.
Anatomy of stress fractures
Stress fractures can occur in any bone that is compromised due to weakening when repetitive stresses are applied to it. Some bones are more commonly affected. Those bones that regularly bear weight and therefore receive the most shock from high impact activities are more susceptible.
The tibia (the larger of the two bones in the lower leg, referred to as the shin bone) is the bone involved in the highest percentage of stress fractures. The fibula (the other lower leg bone), the metatarsals (the long bones extending from the heel to the toes), and the femur (the thigh bone) are also commonly involved.
In the next part of this two part series, we will look at the causes, symptoms and treatment for stress fractures.