The thighbone is the long, strong bone that runs from your hip to your knee. Its scientific name is the femur, and it's the largest and strongest bone in the human body.

Your thighbone does more than you might think. It supports your entire body weight when you stand, walk, or run. When you kick a soccer ball, jump off a diving board, or climb stairs, your thighbone is handling tremendous force. The top of the thighbone fits into a socket in your hip like a ball in a cup, which lets your leg swing in different directions. The bottom connects to your knee joint, working with your shinbone to help you bend and straighten your leg.

Because the thighbone is so thick and dense, it can support incredible weight without breaking. A healthy adult femur can withstand forces of over 1,000 pounds before fracturing. This strength comes from the bone's unique structure: it's hollow in the middle (which makes it lighter) but surrounded by thick, compact bone (which makes it strong). Inside that hollow space is bone marrow, which produces blood cells your body needs.

If you've ever seen a diagram of a skeleton, the thighbone is the long bone that slants slightly inward from hip to knee, giving your legs their shape and strength.