Our joints are pretty amazing marvels of engineering, but they don’t last forever. As we age, or if we suffer certain injuries, the smooth, slippery white cartilage covering the ends of our bones begins to fray and degrade. This causes osteoarthritis (OA), or ‘wear-and-tear’ arthritis. As the cartilage thins and disappears, the bones can even grow spurs that grate against each other, causing swelling and pain. It’s a major cause of disability, and there’s currently no cure—other than joint replacement, which is a pretty big deal and isn’t available for all joints. About 27 million Americans already have osteoarthritis; about 1 in 2 will suffer from some form of the disease over their lifetime. Those are lousy odds.