Femur

The femur transmits the weight from the ilium to the upper end of the tibia. This beautifully shaped bone is the longest and strongest in the body, possessing a shaft and two extremities.

The upper end of the femur consists of a head, neck, and a greater and lesser trochanter. The head is slightly more than half a sphere, being entirely smooth and covered with articular cartilage except for a small hollow just below its centre, the fovea which provides attachment for the ligament of the head of the femur. Connecting the head to the shaft is the neck which is approximately 5cm long and forms an angle with the shaft of 125°. This angle varies a little with age and sex. The neck is flattened on its anterior and posterior surfaces forming an upper and lower border, both being rounded; the upper concave in its long axis, the lower being straight. Thee anterior surface joins the shaft at the intertrochanteric line, the posterior at the intertrochanteric crest which is marked at its centre by the large quadrate tubercle.

The greater trochanter is situated on the lateral aspect of the upper part of the shaft lateral to the neck. It is a large quadrilateral process, having an upper border marked by a tubercle, an anterior border marked by a depression and posterior and inferior borders both roughened for muscular attachment. Its lateral surface is crossed by a diagonal roughened line running downwards and forwards having above it a smooth area covered by a bursa. The medial surface, above the neck, is small and presents a deep trochanteric fossa at its centre.

The lesser trochanter is conical in shape and situated medially, behind and below the neck, being smaller than the greater trochanter. Its tip is drawn forwards and presents a roughened ridge running downwards and forwards.

The shaft is strong, and except for a prominent posterior border, almost cylindrical in cross-section. It is gently convex anteriorly, being narrowest at its centre and growing stouter as it approaches the upper and lower extremities. Its posterior border, the linea aspera, is very rough for muscle attachment, presenting a medial and lateral lip with a central flattened area between. In the upper and lower quarters of the shaft the two lips diverge producing a posterior surface. The upper surface is marked centrally by the narrow vertical pectineal line, whereas the lateral truncated border is continuous upwards with the posterior border of the greater trochanter to form the gluteal tuberosity. The lower surface, between the supracondylar lines above and the condyles below, forms the popliteal surface of the femur. The rest of the shaft is slightly flattened on its anterior, posteromedial and posterolateral aspects.

The lower end of the femur consists of two large condyles, each of which projects backwards beyond the posterior surface of the shaft, the lateral being stouter than the medial. The inferior, posterior and posterosuperior surfaces of the condyles are smooth and continuous anteriorly with the triangularly shaped patella surface, which is grooved vertically producing a large lateral and a smaller medial region. The two condyles are separated posteriorly and inferiorly by the intercondylar notch which is marked on its lateral wall posteriorly by the attachment of the anterior cruciate and on its medial wall anteriorly by the posterior cruciate ligament. The separating lips of the linea aspera continue downwards on to the upper aspect of the medial and lateral condyles as the supracondylar lines, the medial presenting at its lower end as the adductor tubercle.

The lateral surface of the lateral condyle is roughened, being marked just below its centre by the lateral epicondyle below which is a smooth groove for the passage of the popliteus tendon. The medial surface of the medial condyle is also roughened and again marked just below its centre by the medial epicondyle.

Ossification

The primary ossification centre for the shaft appears at 7 weeks in utero. At birth, growth plates separate the bony shaft from the upper and lower cartilaginous epiphyses. A secondary ossification centre appears in the lowe epiphysis shortly before birth. Secondary ossification centres appear in the upper epiphysis for the head at 1 year and in the greater trochanter at 4 years. The last secondary ossification centre appears in the cartilaginous lesser trochanter at 12 years. The upper epiphyses fuses with the shaft at about the eighteenth year, the last to do so being the head. The lower epiphyses fuses with the shaft at about 20 years. The neck of the femur is ossified as part of the body(shaft) and not from the upper epiphysis.

Palpation

The femur is almost completely surrounded by muscles and is only palpable in limited areas. At its upper end, the greater trochanter is an obvious landmark, projecting just a little more laterally than the iliac crest, being easily located by running the hands down from the middle of the crest some 7 to 10cm. The greater trochanter is perhaps easier to feel if the fingers are brought forward from the hollows on the sides of the buttocks in the region of the back pocket. Its posterior border is palpated for about 5cm, running down towards the shaft, while its upper border is an important landmark to locate the level the level of the hip joint.

At its lower end, the femur is well covered with muscle until just above the knee joint. As the fingers pass down the medial side of the thigh the medial condyle can be palpated. This is marked just behind its centre by the medial epicondyle, above which the adductor tubercle can be palpated with the tendinous part of the adductor magnus attaching to it. On the lateral side of the knee, the lateral condyle can be palpated with the lateral epicondyle projecting from its outer surface. At the lower edge of each of these condyles, the line of the knee joint can be palpated particularly as it passes forwards.

If the knee is flexed as much as possible, the patella is seen to move downwards revealing on the front of the knee the two femoral condyles, covered by the lower part of the quadriceps femoris muscle and its retinaculae.