(See also Overview of Sports Injuries.)
Stress fractures develop when repetitive weight-bearing exceeds the ability of the supporting muscles and tendons to absorb the stress and cushion the bones. Stress fractures can involve the thighbone, pelvis, or shin. More than half of all stress fractures involve the lower leg, most often the bones of the midfoot (metatarsals).
Stress fractures do not result from a distinct injury (for example, a fall or a blow) but occur after repeated stress and overuse. Stress fractures of the metatarsal bones (march fractures) usually occur in runners who too quickly change the intensity or length of workouts and in poorly conditioned people who walk long distances carrying a load (for example, newly recruited soldiers). Other risk factors include a high foot arch, shoes with inadequate shock-absorbing qualities, and thinning bones (osteoporosis).
Women and girls who exercise strenuously and do not eat an adequate diet (for example, some long distance runners and some athletes in sports that emphasize appearance) may be at risk of stress fractures. They may stop having menstrual periods (amenorrhea) and develop osteoporosis. This condition is known as the female athlete triad (amenorrhea, disordered eating habits, and osteoporosis).
Standard x-rays are usually done but may be normal until about 2 to 3 weeks after the injury, when x-rays show that the bone is healing from the fracture. Earlier diagnosis is often possible by doing a bone scan or magnetic resonance imaging (MRI). Women who have stress fractures should talk with their doctors about whether they should be tested for osteoporosis.
Treatment includes reduction of weight-bearing on the involved foot. For a while, the person uses crutches and a wooden shoe or other commercially available supportive shoe or boot. Casts are sometimes needed. Healing can take up to 12 weeks. As with other injuries, people can maintain aerobic fitness by doing non-weight–bearing exercises (for example, swimming) until recovery is complete.