Osteoarthritis is commonly referred to as wear-and-tear arthritis. Researchers are finding out that it's not entirely about worn cartilage, though. There are other parts of joint anatomy, like subchondral bone, that play a significant role in osteoarthritis.
Subchondral Bone Explained
Subchondral bone is the layer of bone just below the cartilage. In osteoarthritis, subchondral bone becomes thicker than usual. Evidence has suggested that the thickening happens before the articular cartilage starts to wear away -- an indication that subchondral bone plays a role in the development of osteoarthritis.
Researchers have also discovered that subchondral bone tissue produces several similar cytokines and growth factors (proteins) that can cause inflammation and changes in cartilage tissue.
Biochemical and mechanical properties of subchondral bone in osteoarthritis. Biorheology. 7/26/2004.
Modern Rheumatology. Volume 13, Number 1. March 2003.