I once saw a tv program about the use of cod liver oil for treating arthritis. It described a procedure where the oil was added to a glass of milk and then the mixture was aerated with a whisk (blender). The idea was that you drink this concoction every day until excessive amounts of white wax begins appearing in your ears - this tells you that the mixture has worked its way through your system. After this point you can take the medecine two or three times a weak to maintain pain free, healthier joints.
I have also heard - anecdotally - that evening primrose oil works wonders for arthritis sufferers.