It's a good idea. There are many studied benefits to (intermittent) fasting, for example: https://pmc.ncbi.nlm.nih.gov/articles/PMC11262566/

You think fasting improves knee osteoarthritis independent of weight loss?

fasting is generally highly correlative with weight loss. Its also correlative with reduction in inflammation which is often the underlying cause of arthritis in general. I also would be curious to see what the outcome of fasting would be in a person undertaking an 18 hour fast while consuming enough calories during the feeding window to maintain a caloric surplus.