system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we have kneecaps but no elbowcaps?
gpt
Our legs move in a fairly consistent manner, pretty much just bending one direction at the knee. A kneecap increases the leverage available, and helps aim the leg and knee in the proper direction, helping with this movement. These simply aren't issues with the elbow. Elbows don't need to deal with anywhere near as much force, and benefit from a wider range of motion. Arms need to twist and turn, not just swing.