Well, I have no problem with the concept of anesthetising the dog for the x-rays -- Shiloh had to be when they x-rayed for bladder stones, but I would find another vet! I can't believe he suggested Tylenol and then didn't suggest liver-function checks for the rhimadyl (is that how it's spelled?). Did he draw any blood for baseline numbers before you started the med?

No, 5 1/2 isn't too young for arthritis, unfortunately. Depending on the activity level of the dog, the breed, the weight factor (don't tell Smoke I said anything about that), etc., arthritis can show up even earlier. I hope you find a GOOD vet soon that will take extra good care of Delilah and will keep up with the side effects of her medications. Is this vet an older fellow? Sometimes, the older vets/doctors get so hidebound in what they learned umpteen years ago.....

Prayers and crossed paws for you both.