What is Osteoarthritis?

Osteoarthritis (OA), or degenerative joint disease, is the most common form of arthritis. It most often affects middle-aged and older people, involving the neck, lower back, knees, hips and fingers. Nearly 70 percent of people over the age of 70 have x-ray evidence of the disease, but only half of these people ever develop symptoms.

It may also occur in joints that have suffered previous injury, been subjected to prolonged heavy use, or damaged by prior infection or inflammatory arthritis. Patients with OA experience pain and loss of function.

Elderly woman gripping sore knee on sofa



OA results from degeneration of the joint cartilage. The causes of cartilage loss are multiple. Some kinds of OA are known to be hereditary, including the common form that causes enlargement of the knuckles. Current research focuses on this genetic abnormality as well as new methods studying cells, chemistry and function of cartilage. These efforts are creating rapid progress in our understanding of OA. In most people, cartilage breakdown is due to both mechanical (“wear and tear”) effects and biochemical effects.



OA is suspected when pain develops in the commonly involved joints. It may be confirmed by a physical examination, x-rays and by ruling out other types of arthritis. Since it is so common, it may be present simultaneously with other types of arthritis.

Health Impact


  • OA affects more than 21 million Americans.
  • OA is the most common type of arthritis and a leading cause of disability in the U.S.
  • Virtually everyone over the age of 75 is affected in at least one joint.
  • Women are generally affected at a younger age than men.
Man gripping sore knee sitting on the sofa


Therapy for OA includes both medication and other treatments that help to relieve pain and improve joint function. Drug therapy should begin with simple pain relievers (acetaminophen) and progress to nonsteroidal anti-inflammatory drugs and/or intermittent corticosteroid injections. Recently, several thick liquids that resemble normal joint fluid have been approved for use by repeated injection in the knee joints. In addition, there is some evidence suggesting that some dietary constituents may have a beneficial effect.

Other therapies include patient education, occupational and physical therapy to restore joint movement and increase strength and aerobic capacity, reduction of weight on painful joints and application of heat and cold to relieve pain. Joint surgery to repair or replace seriously damaged joints may be required to end pain and restore functional mobility.