What Is It?

When a bone breaks or cracks, the injury is called a fracture. The leg has three bones that can fracture - the femur (the thighbone) or the tibia and fibula in the lower leg. When a crack or break involves the knobby end portions of these bones that are part of the hip, knee and ankle joints, the fracture is more complicated. This article describes only fractures of the straight shafts of the three long leg bones.

Femur Shaft Fractures The femur is very strong, so it takes a lot of force to fracture this bone in healthy people. The femur usually fractures during high-impact trauma, especially in automobile accidents, industrial accidents, falls from high places, or gunshot wounds to the thigh. If a femur fracture follows a low-impact bump or fall, this may be a sign that the femur has been weakened by an illness such as osteoporosis or cancer.

Femur fractures have the potential to cause dangerous, sometimes life-threatening complications, such as significant bleeding inside the thigh, with blood loss of one quart or more. A femur fracture also may cause blood clots to form within the large veins of the thigh. If these clots break free and travel through the bloodstream, they eventually can lodge in the lungs, creating a life-threatening condition called a pulmonary embolism.

Femur fractures occur in about 3 out of every 10,000 people in the United States each year. Among children, these fractures tend to happen because of a fall from a high place, such as a tree or the top of a slide. In adults, these injuries usually are related to motor vehicle accidents (either as a passenger or pedestrian) or to on-the-job trauma. The number of femur fractures caused by gunshot wounds has risen significantly in recent years.

Tibia Shaft Fractures The tibia (shinbone) is the larger of the two bones of the lower leg. Like femur fractures, tibia fractures often occur because of direct, high-impact trauma, especially during motor vehicle accidents. However, the tibia also can fracture from a low impact, even in healthy people, if the lower leg is bent or twisted at just the right angle.