Eli5: Why do knees have kneecaps, but elbows dont have elbowcaps?
In: Biology
Other answer is right from an evolutionary view, but I read the question a bit differently, so my answer is a bit different.
We have kneecaps and not elbowcaps because we have kneecaps and we don’t have elbowcaps.
A “cap” in this case is a distinct bone, not just the hardness on a joint. You knee joint is made up of a femur, a tibia, a fibula, and a patella. The patella is a separate bone the forms the hard part of your knee.
The elbow is structured differently. Your arm has a humerus, a radius, and an ulna. The radius and ulna form your lower arm, the humerus is your upper arm. The elbow is a spur on the ulna.
So we don’t call it an elbowcap because we don’t have a distinct bone there.
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