There are over 100 different types of arthritis, containing monoarthritis (where only one joint is affected) and oligoarthritis (where multiple joints are affected). According to the Centers for Disease Control, roughly 54.4 million U.S. adults are diagnosed with some form of arthritis per year. As we age, the cartilage in our joints wears down, causing painful bone-on-bone rubbing, inflammation, stiffness, and pain. While it is possible for arthritis to develop in any of the joints, the fingers, elbows, shoulders, lower back, hips, and knees are among the most common.