Femur

The femur is the longest and thickest bone in the human skeleton. It is tubular, containing abundant marrow. It is covered and moved by the longest, largest and most powerful muscles in the body, such as the sartorius, quadriceps, and adductor magnus muscle. It is commonly known as the thigh bone.

Anatomical Description

The femur is composed of a body (shaft), and two ends: the proximal end and the distal end. The shaft of femur (corpus femoris) is cylindrical, slightly twisted about its axis, and curved forwards. Its anterior side is smooth, while its posterior surface features a rough linea aspera, which is a long ridge of bone that serves as site of attachment to muscles.

The linea aspera is divided into two lips, the lateral and the medial lip. The lateral lip is the continuation of the gluteal tuberosity. However, in the lower third portion of the femur, it runs down laterally as it extends to the lateral condyle. The medial lip, on the other hand, runs down the length of femur but it swerves out medially in the lower third portion of bone as it curves to the medial condyle.

The proximal, or upper, end has two rough protrusions at the junction with the shaft. These protrusions are the greater and the lesser trochanter. The greater trochanter juts out upwards and backwards, making up the lateral part of the proximal end of femur. Meanwhile the lesser trochanter is located on the posteromedial surface of proximal end of the bone. The intertrochanteric line extends between the greater and the lesser trochanter on the anterior aspect of upper end of femur, while the intertrochanteric crest runs on the posterior side between the these two protrusions.

The neck of the femur arises from the medial aspect of its proximal end, between the greater and lesser trochanter. Then it projects upwards and medially, ending up in a spherical portion, which is called the head of femur (caput femoris). The neck is slightly flattened on its frontal plane. The head has a small rough pit, which is called the fossa of the head of femur, where the ligament of the head is attached. The head fits in the acetabulum, which is a cup-shaped cavity on the lateral surface of hipbone (pelvis). They articulate with one another.

The distal or lower end of femur is thick and wide, terminating in two condyles; a medial and a lateral conyle. The medial condyle is larger than the lateral one and they are separated from one another by a deep depression called the intercondylar fossa where the cruciate ligaments are attached. The medial surface of the medial condyle and the lateral surface of the lateral condyle feature a medial epicondyle and a lateral epicondyle respectively, which are small bone projections that serve as attachments for ligaments and tendons.

Below, the anterior side of right femur, with its different parts.

Below, posterior side of right femur. Notice the linea aspera and the lateral and medial lip.