From Carol & Richard Eustice,
Your Guide to Osteoarthritis.
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About.com Health's Disease and Condition content is reviewed by Kate Grossman, MD

Anyone Can Develop Osteoarthritis

Osteoarthritis, one of more than 100 types of arthritis and related diseases, is the most prevalent type of arthritis. In the United States, about 21 million people live with the disease. Osteoarthritis is most common among adults over 65 years old but people of any age can develop the disease. Prevalence rises significantly after age 50 in men and after age 40 in women. According to the American College of Rheumatology, 70 percent of people over the age of 70 have x-ray evidence of osteoarthritis.

Wear-and-Tear Arthritis

Osteoarthritis is caused by the breakdown of cartilage in one or more joints. Cartilage is composed of 65 to 80 percent water, collagen (fibrous proteins), proteoglycans (proteins and sugars which interweave with collagen), and chondrocytes (cells that produce cartilage). Cartilage is a hard but slippery tissue which serves as a cushion between the bones of joints, allowing the bones to glide over one another. Cartilage also absorbs shock from physical movements.

When cartilage loss occurs, the joint can deteriorate to the point of rubbing bone against bone. Changes in structures around the joint (muscles and tendons), fluid accumulation, and bony overgrowth (e.g., osteophytes or bone spurs) can develop, causing severe chronic pain, loss of mobility, and disability.

Osteoarthritis is also known as degenerative joint disease, DJD, wear-and-tear arthritis, and osteoarthrosis. The disease can affect joints in the:

• fingers
• hips
• knees
• feet
• spine

Based on x-ray evidence, the distal and proximal interphalangeal joints of the hand are most commonly affected by osteoarthritis, though they do not usually exhibit typical symptoms associated with the disease.

• Hand Illustration from ASSH

The hips and knees are the next most common sites of osteoarthritis and are almost always symptomatic. The first metatarsal phalangeal and carpometacarpal joints also are common sites of osteoarthritis observed on x-ray but the shoulder, elbow, wrist, and metacarpophalangeal joints are rare sites of osteoarthritis unless related to injury or trauma.

Osteoarthritis Risk Factors

Along with advancing age, other risk factors for osteoarthritis include:

• Female gender
• Injury to joints
• Repetitive use of joints
• Overweight or obesity
• Family history

By 2030, approximately 20 percent of Americans will be over 65 years old and at high risk for developing osteoarthritis.

_{Sources:
Handout on Health. NIAMS. 7/7/07. http://awww.niams.hin.gov/hi/topics/arthritis/oahandout.htm
Osteoarthritis. The Johns Hopkins Arthritis Center. 7/07/07. http://www.hopkins-arthritis.org/arthritis-info/osteoarthritis/clinical-presentation.html
Osteoarthritis. American College of Rheumatology. 7/7/07. http://www.rheumatology.org/public/factsheets/oa_new.asp?aud=pat}