The Anatomy of the Femur

The femur is the thigh bone, the largest and strongest bone in the human body. It supports the weight of the body and helps you move. Reaching from the hip to the knee, the femur is extremely hard and not easy to break. A broken thigh bone is one of the few simple fractures that can be considered life-threatening because it can cause significant internal bleeding.

This article discusses the function and structure of the thigh bone, as well as information about conditions that can affect it.

Anatomy

There are four types of bones in your body: long bones, short bones, flat bones, and irregular bones. The femur—the only bone in the upper leg—is a long bone. Longer than they are wide, this type of bone has spongy bone tissue at both ends and a cavity filled with bone marrow in the shaft.

Femur is Latin for thigh, and the bone is commonly referred to as the "thigh bone." The end of the thigh bone closest to the heart (proximal end) is called the femoral head. This is the ball part of the ball-and-socket hip joint.

Below the head of the femur is the neck and the greater trochanter. The greater trochanter attaches to tendons that connect to the gluteus minimus and the gluteus medius muscles. These muscles pull the leg to help with walking and running.

Below the greater trochanter is the lesser trochanter, situated at the base of the neck of the femur. The lesser trochanter is the part of the femur attached to a pair of muscles that help flex the thigh to lift the leg forward.

Below the lesser trochanter is the gluteal tuberosity, which is where the gluteus maximus is attached.

The main shaft of the femur is known as the body. The distal end of the femur (the end furthest from the heart) is where it connects with the patella (knee cap) and the bones of the lower leg (the tibia and fibula).

This end of the femur has a saddle that rests on the top of the tibia. It has rounded edges on either side of the knee joint, known as the condyles. The depression between the condyles is called the patellar groove.

Inside the body of the femur is the medullary cavity, which contains bone marrow. At the ends of the femur are areas of compact bone, which is solid and does not contain marrow. Surrounding the compact bone is spongy bone, which has lots of small cavities dispersed throughout it. The neck and head of the femur are made up of spongy bone.

Function

The femur supports the weight of the body on the leg. All other leg bones are attached to the bottom portion of the femur.

But the femur isn't just for moving the body. There is both yellow and red bone marrow in the shaft of the femur, and they play a critical role in producing blood cells and storing fat.

Blood flow in the femur is hard to measure. It is a significant amount, so much so that a needle inserted into the spongy bone can be used to infuse enough fluid into the bloodstream to offset shock or dehydration.

Associated Conditions

Even though the femur is the strongest bone in the body, it can still be affected by certain conditions, such as fractures, dislocation, and more.

Fractures and Dislocation

Fractures are the most common femur injuries.Though it takes a lot of force to break a femur, certain areas of the bone are more susceptible to fracture than others.

In younger people, femur fractures are usually the result of motor vehicle accidents or other high-impact collisions. In seniors, where bone density has weakened with age, a fall may be responsible. In some older people, a fall-related fracture may involve both the femur and the hip.

A broken thigh bone usually requires surgery to repair it.

Hip dislocation occurs when the head of the femur is pulled away from the acetabulum, the socket in which the head of the femur rests. Without an X-ray, it can be hard to tell if the head or neck of the femur is broken, or if it has dislocated from the hip bone. Depending on how serious the injury is, you could need surgery.

Less Common Conditions

Bursitis can affect any joint in the body, including the hip and knee. It occurs when the bursa—a small sack of fluid that helps with movement in joints—becomes inflamed. This can happen due to injury, infection, or overuse.

Femoral anteversion is a condition that appears in childhood. It happens when the femur bones are rotated inward, leading to inward positioning of the knees and toes.

Legg Calve Perthes disease is a rare childhood disease of the hip joint. It affects blood flow to the head of the femur. A lack of blood causes the bone tissue to die, a condition known as osteonecrosis.

Over time, the bone will regrow, but may have a different shape. It may not fit into the hip as it did before, which could lead to osteoarthritis.

Rehabilitation

Femur fractures generally require surgical repair followed by several weeks of rehabilitation and physical therapy. Dislocations of the hip could require surgery depending on how severe the dislocation is.

Physical therapy (PT) is almost always required.

Summary

The femur is an important bone in the leg and is critical to how the body moves at the hip. Even though it is the strongest bone in the body, it is not immune to injury.

Femoral fractures hip dislocations and other conditions can be very serious if left untreated and can have a long-term impact on movement.