A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running or jumping. Because of this mechanism, stress fractures are common overuse injuries in athletes.Stress fractures can be described as small cracks in the bone, or hairline fractures. Stress fractures of the foot are sometimes called "march fractures" because of the injurys prevalence among heavily marching soldiers. Stress fractures most frequently occur in weight-bearing bones of the lower extremities, such as the tibia and fibula (bones of the lower leg), metatarsal and navicular bones (bones of the foot). Less common are stress fractures to the femur, pelvis, and sacrum. Treatment usually consists of rest followed by a gradual return to exercise over a period of months. Signs and symptoms
Stress fractures are typically discovered after a rapid increase in exercise. Symptoms usually have a gradual onset, with complaints that include isolated pain along the shaft of the bone and during activity, decreased muscular strength and cramping. In cases of fibular stress fractures, pain occurs proximal to the lateral malleolus, that increases with activity and subsides with rest. If pain is constantly present it may indicate a more serious bone injury. There is usually an area of localized tenderness on or near the bone and generalized swelling in the area. Pressure applied to the bone may reproduce symptoms and reveal crepitus in well-developed stress fractures.
Upper extremity stress fractures do occur, but they are uncommon. When stress fractures occur in the upper extremity its commonly in the upper torso and is caused by muscle forces.The population that has the highest risk for stress fractures is athletes and military recruits who are participating in repetitive, high intensity training. Sports and activities that have excessive, repetitive ground reaction forces have the highest incidence of stress fractures. The site at which the stress fracture occurs depends on the activity/sports that the individual participates in.Women are more at risk for stress fractures than men due to factors such as lower aerobic capacity, reduced muscle mass, lower bone mineral density, among other anatomical and hormone-related elements. Women also have a two- to four-times increased risk of stress fractures when they have amenorrhea compared to women who are eumenorrheic. Reduced bone health increases the risk of stress fractures and studies have shown an inverse relationship between bone mineral density and stress fracture occurrences. This condition is most notable and commonly seen on the femoral neck. Other animals
Dinosaurs
In 2001, Bruce Rothschild and other paleontologists published a study examining evidence for stress fractures in theropod dinosaurs and analyzed the implications such injuries would have for reconstructing their behavior. Since stress fractures are due to repeated events they are probably caused by expressions of regular behavior rather than chance trauma. The researchers paid special attention to evidence of injuries to the hand since dinosaurs hind feet would be more prone to injuries received while running or migrating.