My knees are quite jacked up as well with torn menisci so I can relate.
I would still find exercises that work your body. Some variations of major exercises can be quite good and work around your injuries(such as wide stance squats, pistol squats, belt squats, etc). I started doing more calisthenics exercises. As I get older I am beginning to appreciate a higher focus on mobility, flexibility, balance, etc.
Have you tried applying dmso to your knees? I found dmso with pure melatonin powder provides a major relief thanks to their anti-inflammatory properties.
I also really liked bpc157+tb500 peptides for healing old nagging injuries as well.