Osteoarthritis occurs when the joint cartilage that covers the bone ends gradually wears away. This occurs due to time or overuse. For this reason, osteoarthritis is called the "wear and tear" arthritis.
Due to the loss of cartilage, which provides cushioning, the two bones of the joint become in direct contact with each other. This causes joint inflammation, which is responsible for the pain and swelling experienced in osteoarthritis. Bone spurs also develop in osteoarthritis from the friction between the two bones.
Osteoarthritis is more common in the larger weight bearing joints such as the spine, hip, and knee. It is often relieved with rest and exacerbated with activity.