Raven, I'm having the same problems with my 10 year old. I'm not sure it's arthitis as it's been a problem since I got him 9 years ago - per the vet, he has "loose legs" but I suspect in conjunction with that he's getting arthitis. I took them to my brother's for Christmas and everyone thought he was older than my 13 year old
I have him on the NutroMax for older dogs which has Gluwhatever in it, I started putting Synovi-MSM powder in his food about 3 weeks ago (they say it takes 4-6 weeks to see any improvement) and he gets a dose of Metacam every day. I talked to the vet about increasing the Metacam to twice a day since that seems to work for about 1/2 the day but he said increasing will cause liver damage.
It's breaking my heart