A stress fracture is sometimes called a "stress reaction" or "fatigue fracture." This is damage to the outer layer of bone from repeated stress. It is different from a complete fracture because the break doesn't go completely through the thin layer of bone. A stress fracture is considered "microtrauma" or "microdamage."

These types of fractures are most common in runners and soldiers in training, but dancers, gymnasts, and figure skaters are also at risk. These fractures develop because of compressive forces on the bone from landing on one leg after jumping. They can also occur as a result of the repeated action of muscles pulling on the bone.