I will add that I recently joined a new gym - I've been going to a gym for years, but had fallen off in intensity and frequency. New gym, better equipment, yes, a little more time per session, but...
The back issues I've had for several years now? Much reduced.
The knee issues that had popped up again after several years of little trouble? Virtually gone.
I've been going 2+ times a week for less than 3 weeks.
Better than any drug.