The kind of shoes that you wear may, also, inhibit your ability to walk. You should try getting some orthopedic shoes from the podiatrist to help spread out the weight more evenly so that you don't feel as much of a heaviness on your legs. They, even, sell more comfortable shoes in the stores. You could, also, try to wear Dr. Scholl's inserts, so that your shoes are more comfortable to walk in. With your knee, you should try to elevate it as much as possible and put ice on it at least once a day. Muscle strengthening exercises help, as well. However, these are only temporary solutions.
What I think that you may need long-term is knee surgery. I knew a girl in high school who had a sports-related knee injury and went through physical therapy and iced her knee for the pain. However, after about of year or two that, she finally had to get surgery on her knee. I highly recommend that you re-visit your doctor and talk to him/her about other possibilites for the pain in your knee. Ask them if arthritis is the only source of the pain or could there be another possibility? Also, talk to them about the possibility of knee surgurery. If this has been going on for five years, I think that you made, actually, need it and the costs for this could, indeed, be covered by your health insurance. Mainly, I recommend that you just talk to your doctor and explore your options. If your pain is arthritis-related, there may be some kind of medicine that you can take to relieve this pain. So, remeber to keep an oven mind and explore your options, and, just hang in there so that you can, finally, get the proper treatment for your pain! :).