The femur, or thigh bone, is the most proximal (closest to the center of the body) bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs (Figure 2). In vertebrates with four legs such as dogs and horses, the femur is found only in the rear legs. The head of the femur articulates with the acetabulum in the pelvic bone to form the hip joint, while the distal part of the femur articulates with the tibia and patella to form the knee joint. By most measures, the femur is the strongest bone in the body.
The femur is the longest bone of the human skeleton and is located between the hip bone and the knee. It is the only bone in the thigh. This bone is also one of the strongest bones in the human skeleton. It functions in supporting the weight of the body and allowing motion of the lower extremity.
The head (at the proximal extremity) of the femur articulates with the acetabulum of the pelvis to form the hip joint (Figure 1). The lower extremity of the femur (or distal extremity), which is larger, is somewhat cuboid in form and consists of two oblong eminences known as the condyles. The articular surface of the lower end of the femur occupies the anterior, inferior, and posterior surfaces of the condyles. The front or anterior portion is the patellar surface and articulates with the patella. The lower and posterior parts articulate with the corresponding condyles of the tibia to form the knee joint.
The lower and posterior parts of the articular surface constitute the tibial surfaces for articulation with the corresponding condyles of the tibia and menisci.