How Arthritis Disables the Joints

Normal joint: Where two bones meet, our bodies normally provide a simple and effective lubricating system. Ligaments binding the bones together form a capsule within which a thin membrane called the synovium exudes a fluid lubricant. For good measure, the ends of both bones are cushioned by a smooth layer of cartilage.

Osteoarthritis: In this form of arthritis, trouble begins when the protective cushion of cartilage between the bones slowly degenerates. As it disappears, the synovium and the ends of the bones thicken within the joint, leading to the aching stiffness that characterizes the disease.

Rheumatoid arthritis: The culprit here is the synovium, which for unknown reasons becomes swollen and inflamed, leading to irreversible damage to the joint's capsule and protective cartilage. Eventually the unprotected ends of the bones themselves begin to erode.

No ride today