To respond to your comments. The knee that was fixed is strong. I have not had surgery on my other knee yet. I see the doctor tomorrow. As for favoring the right knee, I think I was doing this without really noticing that I was doing so. There really was not reaseon to be favoring it other than when it would hurt when the weather would change.
It's possible that it caused the problems in your left knee, but it's also possible that the cartilage tore for other reasons, like overuse or aging. Did you do physical therapy after you have your surgery? Why have you needed to favor your right knee all this time?