Glucosamine with msm could really help.

Helps to rebuild the sinovial (sp) within the joints. With arthrities the bones start to rub together because of the lack of sinovial fluid and cartiliage.

It doesn't work over night but has shown improvements in all my dogs that had joint problems.

Also sometimes Rimadil can cause an upset tummy. Check with your vet but with my GSD we used Ascription. It's basically an asprin that is coated in mylox to not upset the tummy.