Most people think of fracture as the only injury that affects bones. However, there are two other common bone injuries: stress reactions and stress fractures. Stress reactions are the least severe of these injuries. Essentially, a stress reaction represents the initial stage of a stress fracture. It occurs as a result of the bone being unable to rebuild itself as fast as it is being broken down. If this condition is left untreated, eventually it will develop into a stress fracture, which is characterized by an actual break in the bone. Stresses that lead to stress reactions and fractures usually result from repetitive impact to the affected bone. For that reason, stress reactions are incredibly common among athletes in sports like cross-country running and gymnastics. The main symptom of this condition is a localized point of pain over the part of the bone where the stress reaction has occurred. Stress reactions can occur in any bone; however, they are more common in the bones of the lower leg (e.g., the tibia and fibula) as these bones tend to bear a lot of weight. Because stress reactions do not appear on normal X-rays, they are very difficult to diagnose. In order to confirm the diagnosis of a stress reaction, doctors may recommend a bone scan. This imaging study will show abnormally high levels of bone-building in the region where the stress reaction has occurred. Most often, rest is the recommended form of treatment as it gives the bone a chance to adequately rebuild.