lårbein

Lårbein, known in anatomy as the femur, is the thigh bone and the longest, strongest bone in the human skeleton. In an average adult, its length is about 46 cm, varying with height. It extends from the hip joint to the knee, transmitting weight from the pelvis to the lower leg and facilitating locomotion.

Anatomy: The proximal end includes the spherical femoral head that articulates with the acetabulum of the pelvis, a constricted femoral neck, and the greater and lesser trochanters for muscle attachment. The long midsection, or shaft, is curved and cylindrical, and the distal end forms the femoral condyles that articulate with the tibia and with the patella via the knee joint. The bone contains a central medullary cavity filled with yellow bone marrow in adults, surrounded by dense cortical bone and the protective periosteum.

Development and growth: Ossification begins with a primary center in the diaphysis during fetal life; secondary centers appear in the proximal femoral head and distal femur after birth. Growth in length continues at the epiphyseal plates until late adolescence, when the plates fuse and longitudinal growth ends.

Vascular and nerve supply: The femur receives arterial blood from the femoral artery and its branches, including the profunda femoris and circumflex arteries. Venous drainage mirrors the arterial supply, ultimately draining to the femoral vein. Sensory nerves in the periosteum arise from the femoral nerve and nearby networks.

Clinical notes: The femur bears major loads and is prone to fractures, particularly in the elderly with osteoporosis or after high-energy trauma. Hip (femoral neck) fractures and subtrochanteric fractures affect mobility and may risk avascular necrosis of the femoral head if blood supply is compromised. Fractures of the shaft require stabilization and can involve associated soft tissue injuries.