Osteoarthritis is the most common form of arthritis, affecting millions of people worldwide. It occurs when the protective cartilage on the ends of your bones wears down over time. Although osteoarthritis can damage any joint in your body, the disorder most commonly affects joints in your hands, knees, hips and spine. Osteoarthritis symptoms can usually be effectively managed, although the underlying process cannot be reversed. Staying active, maintaining a healthy weight and other treatments may slow progression of the disease and help improve pain and joint function.