did we just become best friends

Two things will get you killed faster than anything else - too much pain or too much pleasure. Having hairless palms, and knees that eventually give out after 80 years, is the right amount of pain and pleasure.

Imagine a world where everyone looked exactly the same, lived in the same house, ate the same food every meal, and had the same opinion about everything. Contrast (Pain) creates consciousness. The only thing worse than pain and suffering is a world with no pain or suffering, no colors, no contrast, etc.
Having imperfect knees means you have perfect knees - it perfectly lines up with the nature of suffering and goals.