Anatomy of the Femur

The femur (Latin for thigh bone) is the longest and largest bone in the human body. It is a long, cylindrical shaft that extends from the pelvic bone (ischium) to the knee joint (tibia).

The head of the femur articulates with the acetabulum of the pelvis to form the hip bone’s ball-and-socket hip joint. The head is held in place by the neck of the femur, which attaches to the head at a slight angle and by strong surrounding ligaments. The articulating surface is covered with articular cartilage, and the neck is shaped to allow for smooth movement of the hip.

Below the articulating surface of the femur is a roughened area, known as the greater trochanter. This area is attached to tendons that connect to the gluteus minimus and gluteus medius muscles. These muscles help pull the leg forward to assist in walking and running. The greater trochanter is also connected to the iliofemoral ligament, which helps limit over-extension of the hip.

A fibrous cartilage ring, the acetabular labrum, lines the bottom of the socket and deepens it to increase the stability of the hip joint. The iliofemoral ligament, a Y-shaped ligament that attaches the pubis to the femur at the front of the hip, further increases stability. The ischium is reinforced by the iliofemoral ligament, as well as by other fibrous ligaments.

Toward the back of the femur, the neck becomes narrower and slightly longer than the shaft. It is strengthened posteriorly by a ridge of bone called the linea aspera, which splits proximally into the medial and lateral supracondylar lines. The femoral neck is strong laterally but weaker centrally, where it joins the shaft of the femur.

The femoral shaft is somewhat convex forward and slightly flattened posteriorly at the proximal end (near the hip). The proximal end of the femur, near the knee, is thickened by the greater trochanter, which provides attachment for the tendons that attach to the gluteus maximus muscle. The femoral shaft then tapers towards the articulation with the knee cap (patella) and the bones of the lower leg, the tibia and fibula.

A femur fracture is often the result of high-energy injury, such as a motor vehicle accident or a fall from a height. It may also occur as a result of a medical condition such as osteoporosis.

X-rays are the most common way for doctors to diagnose a fracture of the femur. In some cases, doctors may need to perform a computed tomography scan (CT) or an MRI to get a better view of the break and its severity. This type of test involves injecting a contrast solution into the bloodstream and then taking a series of pictures as the fluid travels through the femur. This test can detect the presence of a fracture, as well as any damage to nearby tissue. Occasionally, a femur fracture is not diagnosed until after the patient has already developed significant pain and discomfort.