Osteoarthritis is the most common form of arthritis in the knee. It is a degenerative, “wear-and-tear” type of arthritis that occurs most often in people 50 years of age and older, although it may occur in younger people, too.
In osteoarthritis, the cartilage in the knee joint gradually wears away. As the cartilage wears away, it becomes frayed and rough, and the protective space between the bones decreases. This can result in bone rubbing on bone and produce painful bone spurs.