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What Is Osteoarthritis?

Osteoarthritis is a common, degenerative joint disease 1

Osteoarthritis, also called osteoarthrosis, is the most common form of arthritis. With the rapidly aging population, the worldwide prevalence of osteoarthritis is approximately 10% and it is estimated that more than 50% of those aged over 50 years are affected. In most developed countries, osteoarthritis has now become a major public health issue.
In healthy people, joints are covered by a layer of cartilage that cushions and protects the bones against wear (see figure). In addition, the joints are lubricated by synovial fluid, which helps to reduce friction during movement. In osteoarthritis, the cartilage thins and eventually wears away, leading to pain as the bones rub against each other. Inflammation usually accompanies cartilage breakdown and contributes to pain and disability. Early on during the disease, increased matrix synthesis and repair occur while osteophytes, or bone spurs, stabilize the joint in order to prevent injurious instability. Later during the disease, irreversible pathologic changes affect most of the joint structures and osteoarthritis is best described as total joint failure. For these reasons, osteoarthritis is a disease which affects all articular structures of the whole joint.

Synovial joint anatomy

Synovial joint anatomy

1. Kuettner KE, Goldberg VM. Introduction. In: Kuettner KE, Goldberg VM, editors. Osteoarthritic disorders. Rosemont: American Academy of Orthopaedic Surgeons; 1995, pp xxi-xxv.