[Angie]

Hi Melissa,
A lot of dogs are prone to arthritis as they get older - it's just a natural part of the aging process, unfortunately. Generally it strikes in the joints and spine, which makes even small movements very uncomfortable.
The main thing you can do to prevent arthritis is to make sure the dog isn't carrying too much weight. This is especially important with big breeds, as their bones and joints are already carrying a lot of weight. Even a little bit too much fat makes a big difference, especially over a long period of time. If your dog is overweight, reduce the calories gradually, and exercise more.
There's not really too much more you can do to prevent it, but there are some things you can do to ease your dog's discomfort if he/she does become arthritic.
A lot more attention has been paid in recent years to pain medication for dogs for arthritis.
There are a variety to choose from - NSAIDs (nonsteroidal anti-inflammatory drugs) which are kind of like Advil for dogs. They work to protect the cartilage and give pain relief simultaneously.
Etogesic is another version of NSAIDs, which is less commonly prescribed but cheaper.
There's also a pain reliever and anti-inflammatory called Deramaxx, which is one of the most modern anti-inflammatory nonsteroids.
Hope this all helps - any more questions, just ask.