Dog Dancer, my Shadow (almost 14) is having the same problems, only she is also peeing. We are getting the same diagnosis from the vet (arthritis, spine etc) We had her urine checked and it came back normal. She is on propalin and medicam.
Not sure what our next step will be but we also want her as comfortable as possible before the dreaded day.
Hope everything goes well for your Shadow.
Bree 12 year old GSD
Keesha 8 year old GSD
Cyrus 7 year old GSD
RIP: All my angels.