In osteoarthritis, the cartilage in the 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 osteophytes (bone spurs).
In addition to age, other risk factors for osteoarthritis include obesity and family history of the disease.
Osteoarthritis develops slowly, causing pain and stiffness that worsen over time.