Femur

The medical name for the thighbone, the longest bone in the body. The lower end hinges with the tibia (shin) to form the knee joint. The upper end is rounded into a ball (head of the femur) that fits into a socket in the pelvis to form the hip joint. The head of the femur is joined to the bone shaft by a narrow piece of bone called the neck of the femur, which is a common fracture site (see femur, fracture of). At the lower end, the bone is enlarged to form 2 lumps (the condyles) that distribute the weight-bearing load through the knee joint. On the outer side of the upper femur is a protuberance called the greater trochanter. The shaft of the femur is surrounded by muscles which move the hip and knee joints.