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Femur Bone: A Brief Description

The femur is known as the heaviest, most extended, and strongest bone in a human body. Here are some critical details about it:

  1. The primary function of this bone is handling weight and ensuring the stability of gait, which is an essential component of the lower kinetic chain.

  2. The weight of the upper body sits on two femoral heads. The capsular ligament is a more robust and thicker sheath that wraps around the acetabulum periosteum and proximal femur. This ligament holds the femoral head in the acetabulum.

  3. Femur's robust shape provides several sturdy attachment points for stronger muscles of the hip and knee, and they all contribute to walking and other propulsive actions.

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Parts of Femur

The femur acts as the origin and attachment point for many muscles and ligaments. It can be divided into three main parts, as follows:

1. Proximal Femur: 

It contains the femoral head pointed in a superior, medial, and slightly anterior direction. Ligamentum teres femoris helps connect the acetabulum to the fovea capitis femoris, a pit on the head. The pyramid-shaped neck attaches the spherical head at the apex and the cylindrical shaft at the base. They are attached to two prominent bony protrusions for the movement of muscles and knees, the greater and the lesser trochanter.

2. Shaft: 

It contains a mild anterior arch.

3. Distal Femur: 

The shaft flares out like a cone on to a cuboidal base made of the medial and lateral condyle. They join the femur to the tibia and form the knee joint.

Osteological Features of Femur

Proximal Femur:

At the femur's proximal end, the bulbous femoral head joins with the femur's shaft by the femoral neck. The medically oriented lesser and greater trochanters lie at the neck's base. A rough line named the intertrochanteric line connects the more significant and lesser trochanters on the femur's anterior part. In comparison, there is a smoother intertrochanteric crest that connects the trochanters from the posterior.

Inclination Angle- The angle between the femoral shaft's medial side and the femoral neck, as viewed from the frontal. This angle is greater during birth and decreased during childhood and adolescent development due to added loading stress across the femoral neck while walking and bearing weight. The normal inclination angle is 125-degrees, and it increases the femur's mobility at the hip joint by placing the femoral head and neck in a favourable walking position. There are abnormal angles, too: coxa vara, less than 125-degree and coxa valga, greater than 125-degree. Both the abnormal angles alter the biomechanics and lead to malalignment and other complications.

Femoral Shaft:

The femur shaft courses on an oblique, medial to lateral angle and functions to bring knees' alignment and feet closer to the midline. Shaft's cross-section is in the middle and is circular, but it is posteriorly flattened at proximal and distal aspects. Here is a brief on it:

  1. Posterior Surface Shaft: These are the rough ridges of bones, known as linea Aspera. They then split inferiorly, forming the medial and lateral supracondylar lines. The flat popliteal surface then lies in between.

  2. Proximally: Linea Aspera’s medial border becomes a pectineal line. The lateral border transforms into the gluteal tuberosity, attaching the gluteus maximus.

  3. Distally: Linea Aspera widens, forming the popliteal fossa floor, medial and lateral borders from medial and lateral supracondylar lines. This medial supracondylar line ends when it reaches the abductor, the tubercle, attaching the adductor Magnus there.

Distal Femur:

At the distal femur end, prominent lateral and medial condyles form. An epicondyle then projects from each condyle and acts as an attachment site for collateral ligaments. Medial and lateral condyles then get separated by an intercondylar notch.

Blood Supply

The femoral artery mainly supplies blood to the lower extremity. Here is more about the blood supply around the femur:

  1. Medial circumflex and anastomoses supply femoral heads with Obturator and circumflex artery. The femoral artery is branched into medial and lateral circumflex, and the internal iliac artery is branched into the obturator artery.

  2. The foveal artery comes out of the obturator artery, running through ligamentum teres femoris and acting as a supportive blood supply to the femoral head.

  3. The deep femoral artery's perforating branches supply the distal and shaft portion of the femur. 

FAQ (Frequently Asked Questions)

Q1: Explain the Muscle Division Near the Femur Bone.

Ans: Thigh bone muscle near femur divides into medial, anterior, posterior and gluteal compartments. The femur mainly lies in the anterior compartment. Here is a description of the compartments:

1. Anterior Compartment  

It contains the muscles that are used mainly for hip flexion and knee extension. Hip flexor muscles are pectineus, Sartorius, and iliopsoas muscle.

2. Medial Compartment 

The function of this compartment is leg adduction. It includes the Obturator externus, adductor Magnus gracilis, adductor brevis, and adductor longus.

3. Posterior Compartment 

These muscles are mainly the knee flexors and hip extensors. It contains semimembranosus, semitendinosus, and biceps femur muscles.

4. Gluteal Compartment 

Its superficial layer is composed of medius, minimus, and gluteus maximus, and the primary function of this is abduction, hip extension, and internal rotation. In contrast, the deeper layer is composed of the obturator internus, quadratus femoris, piriformis and inferior and superior gemellus, and this muscle mainly helps with the hip's external rotation.

Q2: What are Some Injuries and Conditions Related to Femur Bone?

Ans: Here are some injuries and conditions related to femur:

Fractured Femur:

  1. Shaft fractures are mainly a high energy injury and might occur in the elderly due to a lower energy fall.

  2. The neck of femur fractures is rapidly increasing and mainly sustained by elderly people due to lower energy falls in the presence of osteoporotic bone. They occur mainly in women. In youngsters, they mainly occur due to higher energy accidents.

Patellofemoral Pain Syndrome:

It is a common injury among sportspersons that occurs as the pain behind or around the patella, mainly with insidious onset. This syndrome's causes are unclear, but genetic, neurologic, biomechanical, or neuromuscular factors might contribute to developing it.

Stress Fractures in Femoral:

It is a condition characterised by an incomplete crack in the femur bone.