How many forms of arthritis are there?

Eventually I think I will be struck by arthritis when I reach a specific age. Just how many forms of arthritis are there currently? Perhaps it is time for me to check it out. My parents have arthritis and so does my pet dog. Currently my pet dog is 16 years old. It shouldn’t be a surprise to find out that my pet dog has arthritis. As movement is one of the best ways to treat arthritis, my dad brings my pet dog for a walk around the house in the morning and evening. Most of the time it is my pet dog which reminds my dad when it is time for a walk.