As people age, the cartilage in their joints becomes compressed, hardened or worn away and can no longer provide the necessary cushion to support healthy joint function. Cartilage is connective tissue that is flexible and covers the ends of the bones in joints such as the knees, hips and vertebrae. Osteoarthritis is a process that causes a breakdown of cartilage, damage of the bones due to bones that rub together, and stretching of surrounding tissues including tendons and ligaments. Symptoms include pain, redness, and swelling. More than 27 million Americans are affected by osteoarthritis.