JOINTS FORMED BY THE FEMUR

At its upper end, the head of femur forms joint with the acetabulum of the hip bone to form the hip joint. At its lower end, the medial and lateral condyles of the femur form joint with condyles of tibia bone and with patellar bone in front to form the knee joint.

GENERAL BONY FEATURES OF THE FEMUR BONE

For the convenience of study, like other long bones of the body it is also divided into the upper end, shaft and the lower end.

The upper end of the femur has following features:

• The head forms more than half a sphere. It has a pit that is situated just below and behind the center of the head and is called the fovea.

• The neck connects the head with the shaft. It makes an angle of about 125 degree with the shaft. It has two borders (upper and lower border) and two surfaces (anterior and posterior surface).

• The greater trochanter is large quadrangular prominence. It is located at the upper part of the junction of the neck with the shaft. It has an upper border with an apex and three surfaces (anterior, lateral and medial surface having trochanteric fossa in it).

• The lesser trochanter is like conical eminence. It projects from the junction of the posteroinferior part of the neck with the shaft.

• The intertrochanteric line (a ridge of bone connecting the two trochanters) and intertrochanteric crest (like intertrochanteric line it also connects the two trochanters) are also present.

Shaft  is the part of bone present between the upper and lower ends. It is almost cylindrical in shape. The shaft as it goes down; it inclines slightly to the medial side. That brings the two knees together, increasing their stability by bringing the knees closer to the body’s center of gravity.

• Linea aspera are broad roughened ridges are present on the posterior surface of the shaft.

• The pectineal line is formed by the medial border of linea aspera at its proximal end.

• The gluteal tuberosity is formed by the lateral border of the linea aspera at its proximal end.

• The medial and lateral supracondylar lines are formed by the medial and lateral borders of linea aspera, respectively, at its distal end.

• In addition to the linea aspera, the shaft also has medial and lateral borders. These three borders thus makes three surfaces of the shaft (anterior, medial and lateral)

The lower end of femur has following important bony features:

• The medial and lateral condyles are formed by expansion of lower end of the femur (they takes part in forming the knee joint).

• The lateral epicondyle is a prominence that is present on the lateral aspect of the lateral condyle.

• The medial epicondyle is a prominence that is present on the medial aspect of the medial condyle.

• The intercondylar fossa is present between the medial and lateral condyles, on posterior surface of femur.

• The adductor tubercle  is a projection that is present posterosuperior to the medial epicondyle.

ATTACHMENTS OF THE FEMUR BONE

Muscles inserted on femur are:

• Piriformis, gluteus minimus, obturator internus, two gemellus, obturator externus, gluteus medius (all are inserted on different aspects of the greater trochanter)

• Psoas major and iliacus (on lesser trochanter)

• Quadratus femoris (on quadrate tubercle)

• Deep fibers of gluteus maximus (into gluteal tuberosity)

• Adductor longus (on medial lip of linea aspera)

• Adductor magnus (into medial margin of gluteal tuberosity)

• Pectineus (on line extending from lesser trochanter to linea aspera)

Muscles originating from femur are:

• Gastrocnemius ( from behind the adductor tubercle)

• Vastus intermedius (from upper part of anterior and lateral surfaces)

• Vastus lateralis (from intertrochanteric line, greater trochanter and lateral lips of gluteal tuberosity and linea aspera)

• Vastus medialis (from intertrochanteric line, spiral line and medial lip of linea aspera)

• Short head of biceps femoris (from lateral lip of linea aspera)

• Plantaris (from lower end of lateral supracondyle)

• Popliteus (from deep anterior part of popliteal groove)

Some ligaments attached to femur are anterior cruciate ligament, posterior cruciate ligament, tibial collateral ligament, capsular ligaments of hip joint and knee joint, fibular collateral ligament and iliofemoral ligaments etc.

SOME CLINICAL ASPECTS RELATED TO THE FEMUR BONE

It s the strongest and longest bone of body so it is not fractured easily, however, two types of fractures are common in case of femur bone:

Intracapsular fracture which is the fracture of femur that occurs inside the capsule of the hip joint. It is more common in old aged people, especially the women and occurs most commonly as a result of minor trip. In this fracture the limb is laterally rotated and is shortened. This fracture can damage the medial femoral circumflex artery, thus leading to avascular necrosis of the head of the femur. In such cases, hip joint is replaced by surgery.

Extracapsular fracture which is the fracture of femur that occurs outside the capsule of the hip joint. It is more common in young people (especially below the age of 16 years). The affected limb is shortened and is laterally rotated. The blood supply of head of femur is not affected and thus no avascular necrosis takes place in this case.

The center of ossification in lower end of femur that is seen by x-rays is used as a medico legal evidence to prove that the dead new born was nearly full term and was viable.