My mum has been walking with a stick for about 3 years, pain in both legs from arthritis , Within a week of going there last June she was saying she felt better and by 2 weeks she was climbing trees to pick cherries..... , she stayed for a month in June and a month in September last year and then went back to the UK and the arthritis has not returned , she only stayed in Bulgaria for a month this year but still it has not returned.
Im sure it is the lack of humidity , Bulgaria is very dry compared to the UK