Fact is, from day one I feel better. I have only made it to thirteen days (twice) so far, but I believe that if you fasted long enough you could get rid of the inflammation that causes rheumatoid arthritis, and if you kept your weight down and didn't eat crap you could keep it down.
Cartilage damage that is already done, however, is not reversible.
That doesn't mean you won't feel a whole lot better though. You can live pain-free with some cartilage damage.
Occasional fasting is good, but perhaps there’s some specific food that’s causing your problem. Next time you break your fast, try having single-food meals of your favorite food ingredients to nail down the ones that are causing the problem. Food sensitivities are most likely to develop with the foods you eat most often: wheat, corn, milk, etc. Any food that causes a noticeable reaction is stressing your immune system: get rid of it.
I went through this 30 years ago. I still remember my first post-fast meal: organic cherry tomatoes. Nothing ever tasted better. A few days later I had a meal of ordinary mushrooms. I never felt worse in my life: it was like Winston Churchill’s depression had descended on me. After doing that I completely eliminated four foods from my life, resolving a host of nagging problems (rashes, arthritis, foot fungus, bad breath, body odor, depression).