femur

The longest and strongest bone of the human body; also the upper bone in the hind limb of a four-limbed vertebrate.

The thigh-bone has a rounded head which articulates with the hip bone. The neck of the bone joining the head to the main shaft is a common site for fracture in elderly people. The bone has two large condyles (knuckles) on its lower end which have extensive surfaces that articulate with the tibia in the knee joint. It has been shown that the adult femur can support a compressive load of about 900 kg/1,990 lb, far more than the weight of the body.