A microscopic break in a bone caused by repeated loading and unloading. Stress fractures are usually slow to develop and are not usually linked to any single injury. They occur when forces applied repeatedly to a bone exceed its structural strength. According to the fatigue theory, bones are more likely to have stress fractures if they are not supported adequately by surrounding muscles; lack of support results in impact forces being transmitted directly to the bones. Consequently, stress fractures tend to be more common in poorly conditioned athletes. Those with brittle bones, such as older people and females with menstrual irregularities (see amenorrhoea) are also more susceptible to stress fractures. Stress fractures are characterized by local pain exacerbated by activity and relieved by rest. Most bones can become stress fractured, but most stress fractures affect the tibia. Stress fractures may be difficult to diagnose, except by bone scan, because they may not appear on an X-ray until well established. Those with a stress fracture should avoid high-impact activities (e.g. running) that impose a lot of mechanical stress on the bone, and replace them with low impact activities (e.g. pool running) to maintain fitness. Ice massage, non-steroidal anti-inflammatories, stretching and strengthening exercises may also be prescribed.
Subjects: Sports and Exercise Medicine.