Suggest Treatment For Pain In The Knees

Hi....my father has pain in his both knees since many years now, his 70 years old and because of that pain his unable to sit properly or even walk and cant do many other things without difficulty....recently a friend told him about the ozone therapy and he is thinking to give it a try as he tried everything before but nothing worked.

My question is, it this therapy really affective and will it heal his pain??? or is it also a waste of time, and if he did gets heal will he stay without having the pain back again after the therapy ends and after passing time or can the pain come back again???

thank you for your help...best regards.