Aging Disorders: OSTEOARTHRITIS. OSTEOARTHRITIS. Normal Sinovial Joint Function Why the Elderly Are Susceptible Osteoarthritis (OA) What is Osteoarthritis? Etiology Pathogenesis Morphology Clinical Significance Osteoarthritis at a Glance. Normal Synovial Joint Function.
The articulation surfaces of these mobile joints, called synovial joints, have a smooth layer of cartilage to (1) allow virtually friction-free movement, and (2) spread the load evenly in weight-bearing joints.
In a healthy joint, the ends of bones are encased in smooth cartilage. Together, they are protected by a joint capsule lined with a synovial membrane that produces synovial fluid. The capsule and fluid protect the cartilage, muscles, and connective tissues.
Cartilage is a protein substance that serves as a "cushion" between the bones of the joints.
Chondrocytes maintain the matrix of type II collagen and proteoglycans to give cartilage its elasticity and high tensile strength.
Over time, the cartilage deteriorates, and its smooth surface roughens. Eventually, if the cartilage wears down completely, you may be left with bone rubbing on bone — causing the ends of your bones to become damaged and your joints to become painful.
Your body goes to work repairing the damage, but the repairs may be inadequate, resulting instead in growth of new bone along the sides of the existing bone, which produces prominent lumps, most noticeable on hands and feet. Each of the steps in this repair process produces pain. The pain and tenderness over the bony lumps may be most marked early in the course of the disease and less evident later on.
Knee replacement surgery can repair damage from osteoarthritis and other inflammatory conditions. The artificial joint has metal alloy caps for your femur and tibia and high-density plastic to replace eroded cartilage within the joint and on your kneecap.