femur

The femur, or thigh bone, is the longest and strongest bone in the human skeleton. It extends from the hip to the knee, bearing substantial body weight and serving as a key lever in locomotion. The proximal end includes the spherical femoral head, which articulates with the acetabulum of the pelvis, the constricted femoral neck, and the greater and lesser trochanters where muscles attach. The shaft (diaphysis) is a dense, cylindrical bone with the linea aspera along its posterior surface. The distal end presents the medial and lateral femoral condyles that articulate with the tibia and, through the patellofemoral joint, participate in knee mechanics.

Anatomical features and joints

The femoral head forms the hip joint with the pelvis, while the distal condyles participate in the knee joint. The neck of the femur, trochanters, and the linea aspera provide attachment sites for a large muscle group, including the quadriceps, adductors, hamstrings, and gluteal muscles. The bone’s trabecular architecture in the head and neck region helps resist bending and shear forces, especially during ambulation.

Vascular and neural supply

The femur receives blood from branches of the profunda femoris (perforating arteries) and the femoral circumflex arteries, with the artery to the head contributing via retinacular vessels. Innervation of the bone and adjacent joints involves branches of the femoral, obturator, and sciatic nerves, reflecting the thigh’s complex muscle and joint innervation.

Development and clinical significance

The femur ossifies from a primary center in the shaft and secondary centers at the proximal and distal ends, with epiphyseal plates that close in late adolescence. Clinically important conditions include hip and femoral neck fractures, osteoarthritis, and avascular necrosis of the femoral head, which are especially relevant in older adults or with high-energy trauma. The femur’s strength and length are essential to posture, gait, and overall mobility.