Sometimes our knees become troublesome because of the way we walk -- we change the way we walk because of our backs!! We tend to try to protect our back and ease the pain, so we change the way we walk -- and that causes big problems with our knees. I've seen this happen many times.
If you can manage it, be aware of how you walk -- try to walk erect, straight, etc., and don't compromise for your back OR your knee. You may have to endure some pain in the process -- put a knee brace on, one of the elastic ones if you don't already have one.
God bless and take care. Hugs, Lee