How come my kneecaps always seem tanner then the rest of my body?
Older skin needs to be sloughed off. Most elbows knees and knuckles will be rougher and thicker skin. Soften with bees wax or any other intense lotion, then use a cloth or scrubbing tool to remove the older skin.
Cuz when you lie down to sunbathe your knees are higher up at an angle. Honestly, I'm guessing cuz I've noticed the same thing.