Osteoarthritis

Cause

Osteoarthritis results from chemical changes in the cartilage that cause it to break down faster than it can be produced. In most cases, experts don't know the cause of this cartilage breakdown. 

In some cases, osteoarthritis may develop as a result of another condition (secondary osteoarthritis).

• Excess weight puts extra strain on the joints, particularly the large weight-bearing joints, such as the knees, hips, and balls of the feet. Experts estimate that every 1 lb (0.5 kg) of body weight means at least 3 lb (1.4 kg) of stress at the knee joint, and even more at the hip joint. Studies show that weight loss can decrease the symptoms of knee osteoarthritis or the chances of developing those symptoms.
• A single major joint injury or several minor joint injuries may result in cartilage changes over time. Although normal activities of everyday life do not cause osteoarthritis, certain types of activities—such as the frequent or repetitive heavy lifting, squatting, and kneeling of some sports or jobs—put repeated stress on a joint and may increase the risk of developing osteoarthritis.
• Muscle weakness increases the chances of developing osteoarthritis. For example, weakness of the quadriceps muscles in the front of the thigh makes osteoarthritis of the knee more likely.
• Daily activity in a joint that is not aligned normally or is more loose and mobile than normal can lead to wear and tear and increase the risk of osteoarthritis.
• A previous infection of the joint may alter the chemical makeup of cartilage and lead to osteoarthritis.
  

In a few people, there seems to be a link between cartilage breakdown and certain factors.

• A family history of osteoarthritis may have some influence on the makeup of cartilage. 
  Unusual metabolic or endocrine conditions, such as excess body iron (hemochromatosis), excess body copper (Wilson's disease), or excess production of thyroid or parathyroidhormones, can lead to cartilage changes and osteoarthritis.
• Defects in joint development or growth can accelerate cartilage loss and lead to osteoarthritis at a younger age. These unusual conditions most commonly involve the hip joint.

Last Updated: April 20, 2007
Author: Robin Parks, MS 
Medical Review: E. Gregory Thompson, MD - Internal Medicine 

Stanford M. Shoor, MD - Rheumatology 

© 1995-2009 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.

This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

•