Long bones are lengthy, cylindrical, hollow in the center, and are characterized by a joint at each end. They are designed to provide structural support, and various muscles attach to these bones to allow movement of the arms and legs. Nerves, veins, and arteries lie along the course of long bones.

The femur, or thighbone, is the longest bone in the human body, extending from the hip socket to the knee. Extending from the shoulder to the elbow, the humerus, or arm bone, attaches to the radius and ulna (forearm). In the lower leg, the tibia and fibula bones extend from the knee down to the ankle. The tibia is the largest bone of the lower leg, and although it supports the body's weight, the smaller adjacent fibula does not provide significant support and functions primarily for muscle attachment.

Fractures of the long bones are among the most common injuries associated with a wide variety of accidents, and a bone injury can occur at any location along the length of the bone. An injury to a long bone may mean disruption of the blood supply and loss of function as well as pain and potential permanent damage. Traction is the common treatment for a broken femur, which places tension on the broken leg, utilizing a weight, until the broken bone is aligned and healed. Other treatments include external casts and internal metal rods and pins.