The Femur is the sole bone of the thigh.

It is the largest and longest bone in the body. It articulates proximally with the pelvis and distally with the tibia of the leg.

The ends of both femurs are farther apart from the midline of the body at the hip than at the knee. The long shafts do not go down straight but angles medially as they descend toward the knee. This allows the knee joint to be closer to the body's center of gravity and provide for a better balance.

A large rounded articular surface which covers the head of the femur fits into the socket formed by the acetabulum (in the pelvis). The head is united to the shaft at an angle by the neck. This is a frequent fracture site in the elderly.

The expanded distal end of the femur has an irregular articular surface. Its lateral and medial condyles both articulate with the tibia of the leg (NOT with the fibula). Between these anteriorly is the smooth articular surface for the patella (= patellar surface).

Prominent projections at the proximal end of the femur (greater and lesser trochanters) serve as points of attachment for several large muscles of the buttocks and thighs; to those at the distal end (lateral and medial epicondyles) are attached the strong ligaments that bind the knee joint together.