Arthritis is one of the most common conditions affecting the joints. It is a broad term that covers a more over 100 diseases. It has everything to do with your joints — the places where your bones connect — such as your wrists, knees, hips, or fingers. But some types of arthritis can also affect other connective tissues and organs, including your skin. About 1 out of 5 adults have some form of the condition. It can happen to anyone, but it becomes more common as you age.