The Anatomy of the Femur

The femur is the largest bone in the human body. It is commonly known as the thigh bone (femur is Latin for thigh) and reaches from the hip to the knee. A human male adult femur is about 19 inches long and weighs a little more than 10 ounces.

The femur is extremely hard and not easy to break. Internal bleeding from a broken femur can be significant, which makes this one of the few simple fractures that can be considered life-threatening.

Anatomy

The femur is found in the thigh. It is the largest bone in the body and is the only bone in the upper leg. The femur is known as a long bone. (There are four types of bone: long bones, short bones, flat bones, and irregular bones.) Long bones are longer than they are wide, with spongy bones at both ends and a cavity filled with bone marrow in the shaft.

The femur of an adult male is about 19 inches long and a bit under an inch in diameter. The proximal end of the femur (the part closest to the heart) is the head of the femur.

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. This is known as an extension of the leg or the hip.

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 (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 of the femur. The distal end of the femur is where it connects with the patella (knee cap) and the bones of the lower leg, the tibia, and fibula. The distal 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 contain spongy bone.

Function

The femur is the primary bone of the leg. It supports the weight of the body on the leg and is capable of carrying 30 times the weight of the body.

The femur is the primary bone of the leg and all other leg bones are attached to the distal portion of the femur.

The medullary cavity contains red bone marrow, which is involved in the production of red blood cells. Over time, red bone marrow is replaced by yellow bone marrow, which helps to store 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

Fractures are the most common condition of the femur. It takes a lot of force to break a femur, although certain areas of the femur are more susceptible. The neck of the femur is the most vulnerable to fracture. Loss of bone density with age leads to an increased chance of fractures in the elderly.

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). It is very difficult to identify the difference between a hip fracture (a broken head or neck of the femur) and a hip dislocation. Some healthcare providers ascribe fractures or dislocations depending on whether the patient's leg is rotated inwardly or outwardly after an injury. In reality, there is no way to tell the difference between a hip fracture or a hip dislocation other than with an X-ray.

Perthes disease is a rare childhood disease of the hip joint. It affects blood flow to the head of the femur. Loss of blood flow causes the head of the femur to stop and the bone tissue dies, known as osteonecrosis.

Femoral anteversion is a twisting of the femurs that appears in childhood. Experts believe this condition could affect as many as 10% of all children. In most cases, the condition corrects itself through adolescence without the need for corrective surgery.

Bursitis can affect any joint in the body, including the hip and knee. A bursa is a small sack of fluid that helps with movement in joints.

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 is almost always required.