The longest, largest and hardest bone in the human body is the Thigh Bone. It is also known as Femur. It is located between the knee and the hip. It has the knee cap at the bottom and pelvis at the top. This bone makes up about one-fourth of a person’s height. It allows us to use our legs for movement. It is connected with the hip by a ball-and-socket joint that allows it the freedom of movement. Femur is considered stronger than concrete.