I haven't had the cortisone shots, but I have had marcaine shots. The marcaine numbs the muscle so it can relax and break the cycle of spasming. It seems to be the only thing that I have tried thus far that works to stop the spasming. The shots are painful, but the relief is immediate. The spasms do return eventually.
Anyway, I've heard that you can get a mixture of the cortisone and marcaine. You may want to ask your doc about that so you can get some immediate relief. I may try the mixture next time. I'm just leary of steroids. I would be very interested to get yawkaw's opinion about the injections and the use of cortisone. I invite anyone else with medical knowledge to respond as well.
I just reminded myself that you were talking about pain from arthritis. Sorry for the diversion. I just posted in another thread that bextra has given me relief from the pain from arthritis. It took some time to work and it doesn't help with other pain that I have. Also, it's expensive, but may be worth a try.