Welcome to the depression board, and hopefully you can find some information here that can help.
I too have knee problems, going on 26+ years now. I was told at 15, that both of my knee caps needed to be replaced, and my tendons needed to be shortened. I had to quit a compeditive swimming career, and pretty much all other activities. At the time, it was going to take eighteen months per leg, done one at a time, for a total of three years of constant pain. At the time I was in High School, so I passed on the therapy and just dealt with the pain since then. Believe me, I understand how depressing it can be.
I seriously don't think that from your description of your medications, the problem with your knee is a side effect. I am an expert on knees. Side effects usually only last as short time, while your body is getting use to the new medication. Since you have been on these for so long, I seriously think you have a physical medical problem with your knee.
First of all, you need to see an orthopedic doctor. The advise to take ibuprofen and exercise you knee is probably just making matters worse, and I can't believe even a mediocre doctor would make this kind of diagnosis.
First of all, your knee is probably highly inflamed. Exercise, even just daily walking, could be making your knee worse. Aleve is a better anti-inflamatory for joints, and the combination of Glucosamine and Chondroitin is highly successful for joint problems. Instead of "exercise", what you need to be doing is specific exercises recommended by your orthopedist. You may need something like a cortisone injection to help with the inflamation. You may actually need physical therapy before doing exercises on your own. Hydro-therapy(water) puts the least stress on your joints.
You can start the Aleve and the Glucosamine and Chondroitin immediately until you can get into seeing an orthopedist as soon as possible.
Hope this helps, and let us know how things are going.