Why do we have kneecaps?
For grown-ups: the science
Kneecaps help your thigh muscles straighten your legs and cover the front of your knee joints.
The patella is a sesamoid bone embedded in the quadriceps tendon. It increases the tendon’s leverage across the knee, improving knee-extension efficiency, and helps protect the front of the joint.
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Transcript
Look at your knee when you bend your leg. What is that little hard bump for?
Your kneecap is a small, round bone at the front of your knee. It sits where your thigh and lower-leg bones meet.
When you straighten your leg, a big thigh muscle pulls on the kneecap. The kneecap helps that pull move your lower leg.
The kneecap also covers the front of the knee joint. It helps protect the joint from small bumps.
So, kneecaps help your legs straighten and help cover your knee joints.