Everyone's tolerance for pain is different, but it sounds like it's more than "mild" to me. In OA, the cushion of cartilage has worn away and the bone is grinding on bone. I don't care if it looks mild on an x-ray - bone on bone hurts!
Another thing that happens is that when a knee is painful, the way you walk changes which puts stress on other joints, muscles and tendons, which causes the pain to seem to spread. You are also probably tensing muscles and tendons around the sore joint in an unconscious effort to protect it. After a while they're naturally going to get tired and sore - even inflamed and swollen, which could account for the difference in size. You might even have bits of cartilage floating around in there.
Exercise will help, just not jarring exercise like running. Cycling is a good, non-weight-bearing exercise to keep the supporting structures around the joint strong. You need to contact the doctor and talk about pain management options. A knee brace, compression wraps, ice packs, pain patches, physical therapy, Synvisc injections, etc. At your age it wouldn't surprise me if the doctor is reluctant to consider a partial knee replacement (I had my first hip done at 37), but it's best to exhaust every other avenue of pain management first.
Thank you very much!!!! This is all new to me. Fortunately, I took the initiative a few days ago to order a specialized compression brace that lacks neoprene. Hopefully, it will help. I will follow your advice and exhaust every option.
I forgot to add that there are pain management specialists out there who will try things your doctor may not. Ask for a referral!
OA pain is a real nuisance, especially considering how far spread the condition is. 46 million people in the U.S. suffer from this debilitating disease, making it the #1 disability in the U.S. today. About 1 in 5 people suffer from this to put it in perspective.
The Arthritis Foundation and the Ad Council have teamed up to spread awareness about this condition to it's sufferers, and to educate them that exercise is the best treatment for OA. I work for a marketing company that is helping the Arthritis Foundation and the Ad Council spread the aforementioned information so that people worldwide can reduce their suffering.
The pain you are experience may be able to be managed through increased activity. Check out some of the PSA's for the campaign I mentioned above here: http://youcastcorp.com/c/90/go/index.php?r=0