You could try switching to a Ketogenic Diet or low carb to help with inflammation. You can also try a high quality fish oil, UC-II undenatured type 2 collagen and that illegal thing that some disc golfers love to do. They are all anti inflammatory and will help with joint pain. Not too sure on the effects that all that will have on arthritis but there are plenty of articles out on the web talking about the benefits of a better diet and how it effects arthritis.
Watch out for too many purines in your diet (Examples of high-purine sources include: sweetbreads, anchovies, sardines, liver, beef kidneys, brains, meat extracts (e.g., Oxo, Bovril), herring, mackerel, scallops, game meats, beer (from the yeast) and gravy) and cut out sugar and high fructose corn syrup. These are the major culprits to inflammation of the joints. I have arthritis and it's a lot worse if I eat too much meat and seafood, especially organ meats. It's OK to drink beer in moderation, but if you drink too much the yeast will have the same effect and cause inflammation. Cutting your grain consumption will help too, as it will help you to lose weight faster. (If it's fed to livestock to fatten them up, it fattens you up too.)
Also... I know this is a lot of stuff all at once... Omega 6 fats are very bad for you without large quantities of Omega 3 fats. You should shoot for a 15 to 1 ratio in favor of Omega 3 fats. In other words, don't eat Omega 6 fats if you can avoid it. These include corn oil, safflower oil, soybean oil. If you are male, you should stay away from soy in all forms except traditionally fermented (expensive tofu) types. All other forms decrease your testosterone by quite a bit, but that's another issue entirely. Just avoid soy. It's tough these days. You'll end up cooking a lot because packaged foods use these oils in just about everything.
If you're saying, "What can I eat?" (I know I did)... you can eat just about anything you can forage and eat without a lot of processing. Veggies and root plants like potatoes and yams are an all you can eat buffet. Cook them in real butter or olive oil. Good cuts of beef or poultry are ok too. I eat a LOT of chicken. Baked chicken is best because restaurants are using Omega 6 oils to fry in. If they use peanut oil (for sure) then go for it.
Once you get used to eating better, the processed foods with Omega 6 oils will begin to taste bad and you'll be in a lot better general health. The arthritis won't be as big a problem either. I've lived with mine for over 20 years.
Good luck and don't stop moving. Movement is the best thing you can do.