Osteoarthritis, a degenerative
joint disease, is the most common form of arthritis
. It is commonly referred to as OA
OA centers primarily the hip or knee, but it often affects the hand and spine as well. It occurs when the cartilage that normally covers and cushions the ends of bones breaks down. As bone rubs against bone, the joint loses shape and alignment, the ends of the bones thicken and form bony growths called spurs. In addition, bits of cartilage or bone float within the joint space. The result is stiff, achy, swollen joints. About 18 million Americans may have some form of this disease.