CHAPTER XIII.
THE LOWER EXTREMITIES.
The lower extremities resemble the upper very closely
in the arrangement of the bones, muscles, arteries, and
nerves, though modifications occur, due to the difference
in function of the lower limbs. There is one long bone
in the upper part or thigh, the femur, and two in the
lower part or leg, the tibia and fibula, while over the
knee-joint is the patella or knee cap. The ankle has
seven bones and the foot nineteen like the hand.
The Femur.—The femur is the longest bone in the body, being about one-fourth the height of the person. It inclines toward its fellow at the knee in order to bring the knee-joints near the center of gravity in walking, the amount of inclination varying with the width of the hips and the height of the person. On account of the greater width of hip the tendency to knock-*knee is greater in women than in men.
The shaft of the femur is enlarged at the extremities and is slightly curved forward, the concavity being strengthened at the back by a longitudinal ridge, the linea aspera, along part of which the gluteus maximus muscle is attached. The head, which is covered with cartilage, except for an oval depression for the attachment of the ligamentum teres, one of the ligaments of the hip joint, and which articulates with the hollow of the acetabulum in the os innominatum, projects considerably upward, inward, and forward from the shaft, the neck varying much in length and angle. It is generally more horizontal in women than in men and in rickets the great weight on the softened bone tends to press the head down, causing the deformity known as
