dog arthritis in rear leg

My dog was diagnozied as having some arthritis,including a problem with the rear knee.He has difficulty climbing the stairs.He walks,ok,and everythin else is fine.He is 13 yrs.old. The vet suggested rimadyl,but I hesitate because of possible side effects. Right now he is getting bugffered ascription,and a combination of glucisamine and chondroitin,started it a few days ago.Could anyone give me some good advice,on this situation.He is a high strung dog,and does not want to be picked up,to go up the stairs.I am anxious to find out the best solution.He climbs the stairs,but trips.Thank you.

When my Shelties was 4 months old he jumped off the front porch and broke is his back leg. He was is a cast for 2 months. About 2 years later he stared limping occasionally on the leg. I took him to the vet and he said that he had arthritis due to the injury. He started him on Glycoflex (glucosamine and shark cartilige) everyday. He also gave him Rymadil but told us to use only when he reall needed it. I think since he was started on the Glycoflex he has had maybe 2 Rymadil. The Glycoflex has worked really well for us.