The femur or thigh bone is the longest (length), largest (volume) and strongest (mechanical ability to resist deformity) bone of the human body. The femur consists of a head and a neck proximally. a diaphysis (or shaft), and two condyles distally. It articulates with the acetabulum, the articular cup on the pelvis (hipbone), superiorly, and with the tibia and patella inferiorly. It forms part of the hip and part of the knee.

The femur's head forms a ball-and-socket joint at the hip. The condyles at the knee form a condylar joint.

Other proximal features of the bone include the greater trochanter and the lesser trochanter , two bony projections that allow muscles to attach. Posteriorly the gluteal tuberosity is a rough surface that gluteus maximus attaches to. Beneath this, the linea aspera runs down the back of the femur, which also provides an attachment for the biceps femoris muscle.

The medial and lateral condyles on the distal end, are bumps that fit into corresponding articular facets on the tibia. The gap between the two condyles is called the intercondylar fossa (or notch). Above the femoral condyles are the medial and lateral epicondyle s, above the medical epicondyle is the adductor tubercle .

Parallel structure by the same name exist in other complex animals, such as the bone inside a ham or a leg of lamb .

Disease conditions

If a traction splint is applied right away, a femur fracture is 20% fatal. Without a traction split, it's 80% fatal.