The lower limbs of humans consist of the paired appendages called the legs. Each leg is made up of an upper leg, lower leg, and the foot.

The upper portion of the leg begins at the junction with the pelvic girdle. From the girdle region a bone called the femur inclines downward to the knee joint. The inclination of the femur brings the knees in line with the center of gravity of the body. The femur is the longest and strongest bone in the body. It is a nearly perfect cylinder. At its top end the femur is ball-shaped, so as to fit into the socket of the pelvic girdle. Near the ball-shaped region, the femur flares upward before the main part of the bone descends. The two protrusions that are present are known as the trocanters. They provide leverage for the muscles that...