Osteoarthritis is the most common form of arthritis, affecting millions of people around the world. Often called wear-and-tear arthritis, osteoarthritis occurs when the protective cartilage on the ends of your bones wears down over time. While osteoarthritis can damage any joint in your body, the disorder most commonly affects joints in your hands, neck, lower back, knees and hips. Osteoarthritis gradually worsens with time, and no cure exists. But osteoarthritis treatments can slow the progression of the disease, relieve pain and improve joint function.