I used to be able to ride a bicycle for hours on end in my 20's and 30's. Now I can't look up when bent over in that position, I need a rise in the handlebars to get me almost vertical. I didn't hurt myself. I didn't get in an accident. It is just a fundamentally unnatural position and the discs just started to deteriorate from years of holding that position. My bikes were sized and fit properly, and I was doing everything right and everything felt OK for literally decades until one day it wasn't OK.