Arthritis in Dogs...I missed the signs!

I didn't know it until my dog was in extreme pain, but she had all the classic symptoms of arthritis for months...withdrawn, less social (hiding under the bed) and even losing weight (the last one wan't alarming because she needed to shed a pound or two.) It wasn't until she was in extreme pain and was diagnosed by the vet with arthritis (at only 6 human years old) that I realized I missed the important signals. Now we are looking for effective treatments to get her back to her old self. Anyone have any treatments that worked out well?