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 “coxa vera”, in which the neck is almost horizontal. Extending upward, outward, and backward from the shaft at the base of the neck, about three-quarters of an inch lower than the head and about on a level with the acetabulum and the spine of the os pubis, is the greater trochanter. This large, irregular prominence and the smaller one of the lesser trochanter, which is at the lower part of the base of the neck posteriorly, are for the attachment of muscles and to assist in rotating the bone. The lower extremity of the femur is larger than the upper and is flat from before backward. Between its two large eminences, the external and internal condyles, is a smooth depression in front, the trochlear surface, for articulation with the patella. The external condyle is more prominent in front, the internal inferiorly, the latter being the longer of the two by about half an inch. The epiphysis at the lower end of the femur is the only one in which ossification has begun at birth. Therefore, if ossification is found there, the child is known to have arrived at full term.
Fig. 74.—Bones of the lower extremity.
(Toldt.)
So many large muscles are attached to the femur that the shaft cannot be detected in the living unless the person is very thin and poorly developed. The outer surface of the greater trochanter, however, and the condyles can be felt.
A string stretched from the anterior superior spine of the ilium to the tuberosity of the ischium passes in the middle just over the upper edge of the greater trochanter. The line thus drawn is known as Nélaton’s line and is of considerable importance in many conditions of the hip. Thus, if the hip is dislocated, the trochanter will be thrown above Nélaton’s line, and in osteomalacia the pelvis sinks and the trochanter is again above the line.
Thigh Muscles.—Of the thigh muscles only a few need be mentioned. One large muscle is the [psoas magnus], which has its origin on the front of the last dorsal and all the lumbar vertebræ, passes down across the brim of the pelvis and under Poupart’s ligament, gradually diminishing in size, and terminates in a tendon that is inserted into the lesser trochanter. It serves to flex the thigh on the pelvis and to rotate it outward. The psoas parvus rises from the last dorsal and the first lumbar vertebræ and does not go out of the pelvis.
The [sartorius or tailor muscle] is flat and ribbon-like and is the longest muscle in the body. It rises from the anterior superior spine of the ilium and is inserted into the upper inner surface of the shaft of the [tibia]. By it the legs are crossed. It also forms the outer side of an important landmark, Scarpa’s triangle, whose base is formed by Poupart’s ligament and the inner side by the [adductor magnus muscle], which passes from the ramus of the os pubis and the tuberosity of the ischium to the linea aspera. The femoral artery bisects the triangle and runs into its apex.
The bulk of the anterior portion of the thigh is formed by the quadriceps extensor, which is really made up of four muscles, the [rectus femoris], whose origin is on the anterior inferior iliac spine and above the acetabulum; the [vastus externus], which comes from the greater trochanter and the upper linea aspera; and the [vastus internus] and crureus, which rise from the neck of the [femur] and the linea aspera. It is inserted into the tubercle of the tibia by the ligamentum patellæ, in which the [patella] lies. Its action is to extend the leg.
At the back and forming the buttocks are the three glutei muscles, the [gluteus maximus, medius, and minimus]. All these rise from the outer side of the ilium and have their insertion on or about the great trochanter. They serve to hold the trunk erect and to extend, abduct, and rotate the thigh.