Several comments here...

1) Always call your vet before doing ANYTHING! A phone call can't possibly cost that much and they are far better trained to answer specific questions concerning your own dog that they have a history with and know any existing medical conditions about that would affect treatment.

2) It's possible what's wrong with the dog could be arthritis, but it could also be a torn ligament, a boney tumor, or even a fracture. NEVER assume you already know what's wrong with your pet and treat the animal based on your assumptions or what you read on the internet unless you have a degree in veterinary medicine.

3) Ibuprophin is DEADLY to pets!!!

4) Aspirin should ONLY be given on the advice of your vet. Aspirin can cause upset stomach, and cause certain known or unknown medical issues with your pet worse! If it turned out your pet does not have the ailment you assumed, then aspirin could seriously interfere with any medications your vet needs to use to help your pet! We just had a case like that yesterday, now the poor dog has to go a whole week without any kind of pain medication because the owner went ahead and self prescribed aspirin without knowing what was wrong with the dog had nothing to do with arthritis!

5) Rimydal is not the safest arthritis drug available. Our hospital stopped using it a few years ago, and now use Metacam, Previcox and a few others.

6) Most vets will require lab work before starting, or periodically during treatment with true arthritis drugs to make sure there is no organ damage going on.