I've had one knee that caused me problems since last fall. Arthritis, I think. It's feeling okay now, but when it was acting up, got pretty bad for quite a while. I'm taking Glucosamine chondroitin (don't think that is herbal) and when it was bad used NSAID's and heating pads.
I learned that a lot of knee pain (including my own, which was immobilizing me somewhat last year) is due to overly tight hamstrings, caused by too much sitting. Since I make it a point of stretching my hamstrings every day now, I have much less knee pain.