The upper (proximal) extremity consists of
- a rounded head (approximately 2/3 of a sphere) which articulates with the acetabulum of the hip bone to form the hip joint. Immediately distal to this is the
- relatively narrow neck of the femur (often broken by the elderly in falls) and
- two protuberances for muscle attachment, the greater and lesser trochanters
Anteriorly, the trochanters are joined by a roughened intertrochanteric
line to which the front of the capsule of the hip joint is attached. Posteriorly,
the trochanters are joined by a large intertrochanteric crest.
The shaft of the femur is smooth except for a ridge which runs down the back of the shaft, the linea aspera. The shaft is virtually surrounded by the quadriceps muscle group (powerful extensors of the knee joint) but the linea aspera serves for the insertion of adductor muscles.
The lower extremity of the femur consists of two knuckle-like condyles which protrude backwards. These articulate with the expanded upper end of the tibia (the tibial plateau) to form the knee joint. Between the distal end of the linea aspera and the femoral condyles, the posterior surface of the femur is very smooth and forms the floor of the popliteal fossa which contains the main neurovascular bundle.
