Many people seem to believe that arthritis, especially in the knee, is caused by excessive movements such as walking or running. This means that they also think once they get arthritis, they should stop doing all of that. In reality, this is not true. Even if you were to get arthritis in the knees, you should still walk, run, and get in as much exercise as possible. Why is this so? Well, before we answer that, let us talk about what arthritis is.