What is osteoarthritis (OA)?

Updated: Jun 10, 2020
  • Author: Carlos J Lozada, MD; Chief Editor: Herbert S Diamond, MD  more...
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Answer

Osteoarthritis is the most common type of joint disease, affecting more than 30 million individuals in the United States alone (see Epidemiology). It represents a heterogeneous group of conditions resulting in common histopathologic and radiologic changes. It has been thought of as a degenerative disorder arising from biochemical breakdown of articular (hyaline) cartilage in the synovial joints. However, the current view holds that osteoarthritis involves not only the articular cartilage but also the entire joint organ, including the subchondral bone and synovium.

Osteoarthritis predominantly involves the weight-bearing joints, including the knees, hips, cervical and lumbosacral spine, and feet. Other commonly affected joints include the distal interphalangeal (DIP), proximal interphalangeal (PIP), and carpometacarpal (CMC) joints. This article primarily focuses on osteoarthritis of the hand, knee, and hip joints (see Pathophysiology). For more information on arthritis in other joints, see Glenohumeral Arthritis and Wrist Arthritis.


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