One or more painful joints resulting from degeneration of cartilage in the joints. When cartilage thins, bone just beneath the cartilage thickens to absorb more impact. On x-ray, there is a smaller amount of separation between bones than is normal (this is caused by thinning of cartilage ). Thickening of bone at the edge of a joint can create ridges of bone. When a ridge of bone is seen on a 2-dimensional x-ray it is called a bone spur in x-ray reports. Osteoarthritis commonly occurs more in fingers, thumb and wrist, knees, hips and spine. It is more common after age 45.