The patella, also known as the knee cap, is a thick, circular-triangular shaped bone that covers and protects the knee joint.
It is the largest sesamoid bone in the human body.
A sesamoid bone is one that floats. You can move your patella from side to side, it is not going anywhere it just has some freedom to move. The reason it has the ability to move is because if your knee cap was held into place as tightly as your other bones are, your knee would not be able to bend. The patella floats around and moves with your quadriceps muscles to make sure it is protecting the joint no matter which way you are going.
Your knee cap acts like a shield to protect your knee joint from injury. If the knee cap was not there, every time you landed on your knees it would feel like your elbow does when you bump your funny bone. It would hurt a lot and it would hurt often!
