Good morning Grandslam!...and Welcome to our Chronic Pain forum! 
I know nothing about your condition, but did look up some information on it and possible treatments. I found one self injectable med called "Enbrel" athat treats both conditions. Have you possible tried this?
Also, we all certainly understand the meaning od Chronic Pain, and the woes of possible withdrawal if meds are not reduced correctly. I was one of those members who reduced my Oxycontin level way too quickly by myself and not under a Dr's care...and it was rough to say the least, and something I will never do again without one.
Oxycontin can be a very good ER med if dosed correctly, and I was on it for several years. At the moment I have been switched over to Fentanyl, and I much perfer it over the Oxy, as it is a much smoother transation from mpain to relief, and visa versa. Every one is different of course, so it will be a trial and error for each person to see what brings the best relief.
If you should happen to have to come off the Oxycontin, it can be done with little effects of withdrawals, as long as your Dr knows what he/she is doing and willing to do this for you. I really cannot answer your question properly for you, but thought I would share some of my thoughts, in hopes that some of it will be of benefit for you.
Again, Welcome!...and enjoy the forum...and its members!
Take care,
SE