I think sometimes lab tests are in error. The clinical signs you mention could be seen with Addison's disease, though. If the results were surprising it may be that there is a need to rethink this diagnosis but the only way to tell is to check. This stuff is outrageous in price. I still like aspirin a lot.
Some vets use phenylbutazone and believe that it works better in many patients.
Little things like providing a warm or soft bed, spending a few minutes massaging sore legs or ensuring regular moderate exercise can all help. If your dog is overweight the single best thing you can do is to help him or her lose weight. This does more to relieve the pain associated with arthritis than medications in many instances. He prescribed 60 mgs rimadyl to be given twice daily for the pain associated with this injury. In reading the info on the drug on your site, it appears that this drug is indicated for arthritis, not soft tissue trauma.