The thigh bone (femur) is the largest in the human body. It’s located between the pelvis and the knee (upper leg). It’s classified as a long bone, making up approximately one-third of our height. The head of the femur fits into the acetabulum (hip joint) to form the hip joint, which is ball and socket type. The head of the femur is spherical (eminentia spherica).

The long bone provides an attachment site for muscles, tendons, ligaments, and blood vessels. At birth, it makes up about one-quarter to one-third of total length in children and adolescents and about one-sixth of total length in adults. It has a diaphysis (shaft) and two epiphysis (extremities).

The upper end is called the head, the flat part below it is called the neck, and together they are known as the “collum anterius” or “longitudinale superius”. The lower end is called the condyle, and the rounded protrusion below it’s called the trochanter.

As a kid, your thigh bone was about 9 centimeters (3.5 inches) long compared to its current length of 25 centimeters (10 inches). So how is it possible that your thigh bone can double in size?

To ensure bone health, the thigh bone must grow and remain strong. During puberty, the chemical signal for growth is sent out from a part of the brain. This chemical signal stimulates two other areas in the brain: one releases a chemical that signals bones to get larger and stronger, while another tells muscles to get bigger.

As an adult, the femur is about one-third of total height. The head is partly encircled by a thin layer called articular cartilage, which cushions and lubricates movements between the ball and socket joint surface.