In the United States alone, there are nearly 40 million people diagnosed with a form of arthritis. As a medical condition, arthritis is actually an umbrella term for several different types of conditions that are considered arthritis. Though there are many different forms of it, arthritis is most commonly known as a disease that causes the joints in our bodies to lose their flexibility and become strained. Most often, the joints affected are found within our extremities, such as our hands and feet.