Osteoarthritis is the most common form of arthritis, affecting millions of people worldwide. It occurs when the protective cartilage that cushions the ends of the bones wears down over time. A type of arthritis that occurs when flexible tissue at the ends of bones wears down.

Although osteoarthritis can damage any joint, the disorder most commonly occurs in the weight-bearing joints of the hips, knees, and spine. It also affects the fingers, thumb, neck, and large toe.

In a healthy joint, a coating of tough but smooth and slippery tissue, called cartilage, covers the surface of the bones and helps the bones to move freely against each other. When a joint develops osteoarthritis, part of the cartilage thins and the surface becomes rougher. This means the joint doesn’t move as smoothly as it should.

When cartilage becomes worn or damaged, all the tissues within the joint become more active than normal as the body tries to repair the damage. The repair processes may change the structure of the joint, but will often allow the joint to work normally and without any pain and stiffness. Almost all of us will develop osteoarthritis in some of our joints as we get older, though we may not even be aware of it.