Femur

Original Editor - Daphne Jackson

Top Contributors - Lucinda hampton, Kim Jackson, Evan Thomas, Admin, Daphne Jackson, Joanne Garvey, WikiSysop and Joao Costa

Introduction

The femur is the longest, heaviest, and strongest bone in the human body.

• The main function of the femur is weight bearing and stability of gait. An essential component of the lower kinetic chain.
• The upper body’s weight sits on the 2 femoral heads. The capsular ligament is a strong thick sheath that wraps around the acetabulum periosteum and proximal femur holding the femoral head within the acetabulum.
• Robust shape of the femur provides many sturdy attachment points for the powerful muscles of the hip and knee that contribute to walking and other propulsive movements.

Osteologic features of this long bone include:

1. Proximal Femur consists of: femoral head - pointed in a medial, superior, and slightly anterior direction. Ligamentum teres femoris connects the acetabulum to the fovea capitis femoris (a pit on the head); neck (Pyramid-shaped) attaches the spherical head at the apex and the cylindrical shaft at the base; 2 prominent bony protrusions, the greater trochanter and lesser trochanter, that attach to muscles that move the hip and knee.
2. Shaft - has a mild anterior arch.
3. Distal femur - shaft flares out in a cone-shaped manner onto a cuboidal base made up of the medial and lateral condyle. Medial and lateral condyle join the femur to the tibia, forming the knee joint

Osteologic Features

Proximal Femur

At the proximal end of the femur, the bulbous femoral head is joined to the shaft of the femur by the femoral neck. At the base of the neck are the medially oriented lesser trochanter and laterally placed greater trochanter. A rough line called the intertrochanteric line connects the greater and lesser trochanter on the anterior aspect of the femur, while the smoother intertrochanteric crest connects the trochanters posteriorly.

• Angle of Inclination

ie The angle between the femoral neck and the medial side of the femoral shaft viewed from the frontal. Greater at birth but decreases during childhood and adolescent development due to loading stresses across the femoral neck in weight-bearing and walking. Normal angle of inclination of 125 degrees increases mobility of the femur at the hip joint by placing the femoral head and neck in a biomechanically favourable position for walking. Abnormal angles -coxa vara less than 125 degrees; coxa valga greater than 125 degrees. Both alter hip biomechanics, leading to malalignment and complications.

Femoral Shaft

The shaft of the femur courses on an oblique lateral to medial angle, functioning to bring the alignment of the knees and feet closer to midline.

A cross section of the shaft in the middle is circular but flattened posteriorly at the proximal and distal aspects.

• Posterior surface shaft - roughened ridges of bone, called the linea aspera (Latin for rough line). These split inferiorly to form the medial and lateral supracondylar lines. The flat popliteal surface lies between them.
• Proximally - medial border of the linea aspera becomes the pectineal line. The lateral border becomes the gluteal tuberosity, where the gluteus maximus attaches.
• Distally - linea aspera widens and forms the floor of the popliteal fossa, the medial and lateral borders form the medial and lateral supracondylar lines. The medial supracondylar line ends at the adductor tubercle, where the adductor magnus attaches.

Distal Femur

Prominent lateral and medial condyles are found at the distal end of the femur. Projecting from each condyle is an epicondyle that act as attachment sites for the collateral ligaments. The lateral and medial condyles are separated by the intercondylar notch.

Blood Supply

The femoral artery is the main blood supply to the lower extremity.

• The medial circumflex and anastomoses mainly supply the femoral head with the lateral circumflex artery and obturator artery (Medial and lateral circumflex are branches of the femoral artery, obturator artery is a branch of the internal iliac artery).
• The foveal artery comes off of the obturator artery that runs through the ligamentum teres femoris as supportive blood supply to the femoral head, but it is not the main source during adulthood.
• The perforating branches of the deep femoral artery supply the shaft and distal portion of the femur.

Articulations

The femoral head of the proximal femur articulates with the acetabulum of the pelvis, forming a "ball-and-socket" joint, in which the femoral head acts at the ball and the acetabulum as the socket. This formation allows for movement at the hip in three planes: flexion and extension in the sagittal plane, abduction and adduction in the frontal plane, and internal and external rotation in the horizontal plane.

Distally, the convex femoral condyles of the femur articulate with the condyles of the tibia, forming the tibiofemoral joint. Movement at the tibiofemoral joint occurs in two planes: knee flexion and extension in the sagittal plane, and internal and external rotation in the horizontal plane.

The patellofemoral joint is formed by the articulation of the patella with the intercondylar/trochlear groove of the femur. During flexion and extension of the knee, the articular surfaces of the patella and femur perform a sliding movement.

Injuries and Conditions

Femoral fractures can occur at the femoral head, shaft, or condyles, with a fracture of the femoral neck being the most commonly fractured location. Osteoporosis is a significant risk factor for fractures of the femoral neck.

Patellofemoral pain syndrome (PFPS) is a common sports-related injury that presents as pain around or behind the patella, typically with an insidious onset. The cause of the condition is unclear, but neurologic, genetic, neuromuscular and/or biomechanical factors may contribute to its development.

Femoral Stress fracture 
A femoral stress fracture is a condition characterized by an incomplete crack in the femur (thigh bone).