The femur head is the highest part of the thigh bone (femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

). It is supported by the neck of the femur.

The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a little forward, the greater part of its convexity being above and in front.

Its surface is smooth, coated with cartilage

Cartilage

Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 in the fresh state, except over an ovoid depression, the fovea capitis femoris

Fovea capitis femoris

The surface of the head of the femur is smooth, coated with cartilage in the fresh state, except over an ovoid depression, the fovea of head of femur, which is situated a little below and behind the center of the head, and gives attachment to the ligamentum teres.-External links:*...

, which is situated a little below and behind the center of the head, and gives attachment to the ligament of head of femur

Ligament of head of femur

The ligament of the head of the femur , or the round ligament of the femur , is a triangular, somewhat flattened band implanted by its apex into the antero-superior part of the fovea capitis femoris; its base is attached by two bands, one into either side of the acetabular notch, and between these...

.

If there is a fracture of the neck of the femur, the blood supply through the ligament becomes crucial. In orthopedic surgery

Orthopedic surgery

Orthopedic surgery or orthopedics is the branch of surgery concerned with conditions involving the musculoskeletal system...

, the head of the femur is important because it can undergo avascular necrosis

Avascular necrosis

Avascular necrosis is a disease where there is cellular death of bone components due to interruption of the blood supply. Without blood, the bone tissue dies and the bone collapses...

 and consequent osteochondritis dissecans

Osteochondritis dissecans

Osteochondritis dissecans , often abbreviated to OCD or OD, is a joint disorder in which cracks form in the articular cartilage and the underlying subchondral bone. OCD is caused by blood deprivation in the subchondral bone. This loss of blood flow causes the subchondral bone to die in a process...

. The head is removed in total hip replacement surgery.