Gabapentin only works for nerve based pain, not athritic changes. I use Metacam for my athritic dogs. It's a non-steriodal anti-inflammtory. It can affect the liver and a few other things. I've never had a dog who had a negative reaction to it. I have several who are on it every day, one who's taken it every day for four years with no problems.

Supplements like glucosomine might help, but they take awhile to build up and become effective, if they work. I've never seen any big changes in my dogs from supplements, but lots of people swear at them.