Sorry to hear you are having knee pain.
I have "wrecked" knees from many years of playing basketball, running, etc., along with a "predisposition" for osteoarthritis.
I have to walk with a cane or a crutch much of the time due to knee pain and stiffness.
However, I can bike. I had taken Denise's advice on the speedplay frogs and had coupled that with additional research. I am using the speedplays which have maximum float. My knees are very happy! They are less painful and more functional than they have been in years!
Zinn, in his book on bike maintainence, identifies speedplay frogs as one of the pedals with the most float.
At the same time, many attest to less float as the key to less knee pain!
Another major factor in knee pain is the overall "fit" of the bike! If you haven't had an extensive "fitting," I'd highly recommend it! My "fitting" lasted 1.5 hours and they had even watched to see just how my knees were "tracking." (Sometimes they recommend "shims" if the knees are not tracking well.) My "tracking" greatly improved with the addition of the speedplays... which meant this was likely to be a good choice for me.
I wish you luck in solving your knee problem.
Keep us posted!
~Wishing you inner peace and abundant joy~