I'm lucky in that none of my problem parts are in my back.
Right knee is... well let's just say I'm going to have to get that fixed one of these days but the longer I wait the better job they can do and it still works well enough for now.
Knees and backs both have the wonderful thing about them: once you screw them up, they won't heal right if you don't use them. But if you use them too much or too little then they won't heal right either.
But how much fun would life be without a few challenges, right?