How does magnetic arthritis jewelry work, and how can you tell the difference between good and bad quality beads?

They don't work. There is no difference, it's all "magic beans." if they worked, would doctors sell them too, so that they could make more money?
Not proven to help. The magnetic therapy products available to consumers have not been proven to help arthritis. Little magnets are sometimes sewn into bracelets. The bracelets may be fashionable, but the magnets do not provide any additional benefits. However, pain is very subjective, so if a person believes he is doing more to treat his pain by wearing magnets, he may truly sense less pain.