Stress fractures are a type of overuse injury. These tiny cracks in your bones develop when your muscles become fatigued and can no longer absorb the shock of repeated impacts. When this happens, the muscles transfer the stress to the bones, creating a small crack or fracture.

Stress fractures are a type of overuse injury. These tiny cracks in your bones develop when your muscles become fatigued and can no longer absorb the shock of repeated impacts. When this happens, the muscles transfer the stress to the bones, creating a small crack or fracture. Stress fractures also can occur with normal usage if osteoporosis or some other disease weakens your bones and leaves them vulnerable. These fractures are often called "insufficiency fractures" because there isn’t enough bone to withstand the normal stress of daily use.

Most stress fractures occur in the weightbearing bones of the foot and lower leg. The most commonly affected site is the second or third long bone between the toes and the midfoot. Stress fractures also can occur in the heel, the outer bone of the lower leg (fibula) and the navicular, a bone on the top of the midfoot. People most at risk of developing stress fractures are athletes who participate in high-impact sports such as track and field, basketball, gymnastics, ballet or tennis; adolescents whose bones have not yet fully hardened; and women, particularly female athletes, who have abnormal or absent menstrual cycles that can result in decreasing bone mass.

Causes
Doing too much too soon is a common cause of stress fractures. Improper sports equipment, such as shoes that are too worn or stiff, also can contribute to stress fractures. A change of surface, such as going from a grass tennis court to one of clay or from an indoor to an outdoor running track, can increase the risk of stress fractures. Errors in training or technique are another cause of stress fractures. Some conditions, such as flatfoot or bunions, can change the mechanics of your foot and make stress fractures more likely to develop.

Insufficiency stress fractures result when the bone itself is weak. Conditions such as osteoporosis reduce the density and quality of bone matter, thus increasing the risk of fracture. Female athletes who experience irregular or absent menstrual periods may also have decreased bone density and an increased risk of stress fractures.

Symptoms
You may have developed a stress fracture if you experience swelling on the top of the foot or the outside ankle; tenderness to touch at the site of the fracture; or pain that develops gradually, increases with weight-bearing activity, and diminishes with rest.

 Treatment
Treatment will depend on the location of the stress fracture. Most stress fractures will heal if you reduce your level of activity and wear protective footwear for two to four weeks. Your orthopedist may recommend that you wear a stiff-soled shoe, a wooden-soled sandal, or a removable short leg fracture brace shoe. Athletes should switch to a sport that puts less stress on the foot and leg. Swimming and bicycle riding are good alternative activities.

Stress fractures in the fifth metatarsal bone (on the outer side of the foot) or in the navicular or talus bones take longer to heal, perhaps as long as six to eight weeks. Your orthopedist may apply a cast to your foot or recommend that you use crutches until the bone heals. In some cases, you may need surgery so that the orthopedist can insert a screw in the bone to ensure proper healing.