Anatomy of the Femur

The femur is the largest and strongest bone in the human body, requiring significant force to fracture it. 1

General Structure

The femur consists of three main parts: the proximal end, shaft (diaphysis), and distal end 2
As the longest bone in the human skeleton, the femur plays a crucial role in weight-bearing and locomotion 1
The femur articulates proximally with the acetabulum of the pelvis to form the hip joint and distally with the tibia and patella to form the knee joint 3

The proximal femur consists of the femoral head, neck, greater trochanter, and lesser trochanter 2
The femoral head is spherical and articulates with the acetabulum to form the hip joint 2
The femoral neck connects the head to the shaft at an angle of approximately 125° in adults 2
The greater trochanter is a large, irregular prominence located at the junction of the neck and shaft, serving as an attachment site for gluteal muscles 2
The lesser trochanter is a smaller projection on the posteromedial aspect of the femur where the iliopsoas muscle attaches 2

The femoral shaft (diaphysis) is cylindrical and slightly bowed anteriorly 1
The shaft has three surfaces (anterior, medial, and lateral) and three borders (medial, lateral, and posterior) 1
The linea aspera is a prominent longitudinal ridge on the posterior surface of the shaft, serving as an attachment site for numerous muscles 1

The distal femur widens to form two condyles (medial and lateral) that articulate with the tibia 3
Between the condyles posteriorly is the intercondylar notch, which houses the cruciate ligaments 3
The patellar surface (trochlea) is located anteriorly between the condyles and articulates with the patella 3
The adductor tubercle is a small prominence on the medial condyle where the adductor magnus muscle attaches 3

The femur has a strong outer layer of compact bone (cortex) surrounding an inner cancellous bone with trabeculae 4
The trabecular pattern in the proximal femur develops progressively during childhood 4
At birth, linearly arranged trabeculae are present but not visible on conventional radiographs 4
By age 5, the trabecular pattern is well-established, with principal medial and lateral groups of trabeculae 4
The internal architecture of the femur is designed to efficiently transmit and distribute forces from the hip to the knee 4

The femoral head begins as cartilage and ossifies at approximately 4 months of age (range 2-8 months) 2
The trabecular pattern develops progressively during childhood, becoming well-established by age 5 4
The proximal femoral growth plate (physis) contributes significantly to longitudinal growth of the femur 5
Complete fusion of growth plates occurs during late adolescence 5

The femur's strength requires significant force to fracture in adults, with motor vehicle accidents being the most common cause 1
In children, femur fractures may raise suspicion for abuse, while in the elderly, they commonly result from falls 1, 2
The proximal femur is a common site for pathologic fractures due to metastatic disease 2
Incomplete atypical femur fractures can occur in patients on long-term bisphosphonate therapy, typically in the femoral shaft below the lesser trochanter 2
The femur is a common site for primary bone tumors, with osteogenic sarcoma having historically been treated with amputation but now sometimes managed with total femur replacement 6