The body mass index is a little clunky as a measure, but for those with knee and back problem, it should be your 1st port of call. Do you have a healthy Body mass index?
If not and you are active, think on this. “Active” normally means 10,000 steps a day. If you are 10kg over weight thats 10 x10,0000 that 100,000 kilos extra than your body expected . Weightlifters brace and prepare!
If you are inactive and slumping in your chair thats a lot of deadweight pressing on knackered back and bum muscles.
“Dude, loose some weight!”
If you have an ok weight, well thats ok. Go you. Thats not the problem!