You and me both, I cannot run at all but stop cycling for more than a week or so and the knee gets more painful. Maybe people would be healthier and need less help if they cycled more.
I had very bad problems with my knees - wear behind the kneecap. It pushes on the knee joint as you straighten your leg. I could hardly get up one flight of stairs and was in pain every day.
I took up cycling and the build up of muscle changes the way the kneecap sits on the joint and so eases the problem. Also I lost about a stone in weight (partly from the cycling) and am currently on the way to losing another stone.
I was feeling good with the weight loss and so started running again. I can do Parkrun 5k in about 31 minutes after 2 months of running and get no problems at all with my knees now.
So I am all for attacking a problem rather than giving in to it. But of course I was fortunate in the issues I had could be dealt with in that way and some cannot.