I second the Speedplay Zeros
1) you can choose to have float or have them fixed. I ride mine fixed I find it greatly helps stabilize my knee.. but they need to be fixed in the proper position.
2) They are easy to get in and out of
3) You don't have to twist your foot as far as some others like Look & Time to get out of the pedals which is good for bad knees.

I too have bad knees.. Loose ligaments in my shoulders, hips and knees. This is greatly benefited by lifting and trying to get those muscles surrounding those joints strong because the ligaments won't hold the joints together so the muscles need to do more then their normal share.

Personally, i have not had much luck with PTs. I know there are good ones out there but I have not found any. However, I have had good luck with a chiro who does more then just chiorpractic.. he evaluates gait, does orthodics etc etc. I have also had great luck with massage in helping knee issues.

I DO have eSoles in my cycling shoes and if you ever have the opportunity to be fitted by Peterson himself do so.

-grace