It depends what the state of your knees is. If you have any cartilage damage, it cannot be rebuilt and you will eventually need surgery.
On the other hand if pain is only due to ligaments and muscles, as most of us aging dudes, biking without mushing helps a lot. That means you first need to learn high cadence spinning. This is not bad at all as it also promotes cardio vascular enhancing workouts, exactly what a 50+ needs; isn't life great?
I started riding about 4 years ago because I couldn't run anymore. My knees were hurting even at rest in bed. One day I woke up with swollen knees after playing volleyball the night before, so I decided to try something less punishing for them. I didn't want to resort to surgery as I had read that the majority of the knee surgeries are not necessary and are mostly quick pain fixes. A surgeon friend of mine recommended non impact exercises, so I tried a rowing machine. It worked but was boring so cycling came to mind. Today I have no pain at all, thanks to cycling. I did twist one knee once while falling from the bike when I was still new with clipless pedals, it took a year before the pain completely went away but it did.
I do take 3 fish oil capsules every morning but that's because my wife said it was good for our brain, skin and heart. It might help on the joints as well, I don't know for sure.