patellofemoral osteoarthritis

Hi razzbery and welcome. I've no medical qualifications just many years of RA and OA and several replacement joints. At a guess I'd say your knees hurt because, as the x-ray showed, you have OA. I don't know much about MRI scans as I've only ever had one but, again at a guess, I'd say the damage done isn't yet enough to register on it. (But do bear in mind, that's purely guesswork on my part.)

The thing is, knees (or any other affected joints) hurt right from the kick off, not just once a lot of damage has been done. Pain relief helps but doesn't, for most of us, take it away. It's a matter of getting the balance between pain relief and being wide awake enough to function properly until the orthopaedic surgeons can do their stuff. (And exercising them to keep the supporting muscles strong - and supporting.)