My recommendation (from experience) is don't start! Exhaust all other options before using opiates for chronic pain.
And for recreational use, I will just say please don't, and good luck to you sir. Really, it will get to where it's not even fun and you're getting "high" just to feel almost normal because there is no longer a high until OD dosages followed shortly after by death as pushing that limit in desperation.
Take care of your body and appreciate your life. And sorry to get all preachy, I just don't want others to have to go through what I did ...