Welcome, Mary. I'm sorry you have reason to be here, but I do think you came to the right place. Things will be a little less (maybe even a lot less) scary pretty soon. The beginning of lung cancer treatment is hard because you don't know just what you have, how it can be treated, or how successful treatment will be. And, of course, your knee is no better than it was at your preop.
I had a total knee replacement in 1998 and my lung cancer was diagnosed in the spring of 2003. At least, I could walk comfortably by then.
Please keep us posted as you go through this strange journey.
Muriel