I have heard of better shoes helping more with feet and lower back problems, but not so much with knee problems.
Have you tried a "joint support" type supplement (with at least glucosamine, chondroitin, and MSM)?
I know of many people, including myself, who these products have helped immensely - especially if your knee problems are related to hard court sports in your younger days.
As a general rule, liquid products will work a bit better, but are more expensive. Also, it is important to take at least the full dosage EVERY day for at least a month to see if you are getting relief. These types of products work very well for osteo-arthritic conditions for most people... but not all.
Hope this helps.