Does Aging Cause Osteoarthritis?

Question: Does Aging Cause Osteoarthritis?

Aging is a known risk factor for osteoarthritis. The disease is often explained as the result of wear and tear on the joints, but there may be a more thorough explanation of what happens to cartilage and joints during the aging process that causes or increases the risk of developing osteoarthritis. Does aging directly cause osteoarthritis? What changes occur during aging that may explain the development of osteoarthritis?

Answer:

Osteoarthritis: Not Inevitable Consequence of Aging

Osteoarthritis is the most common cause of chronic pain and disability in older people. Even though osteoarthritis is not an inevitable consequence of aging (not every older person develops osteoarthritis), there is a strong correlation between age and increasing evidence of osteoarthritis. Actually, 70% of people over the age of 70 have x-ray evidence of osteoarthritis but only half ever develop symptoms.

Age-Related Changes to Cartilage

The breakdown of cartilage due to mechanical wear and tear of the joint is the easiest way to explain osteoarthritis, analagous to car parts wearing out after a car has accumulated many miles. Really, it's more complicated than that. Osteoarthritis can be the result of age-related changes to cartilage matrix components.

Specifically, cartilage degeneration related to osteoarthritis may occur because of the loss of viable cells (chondrocytes) due to apoptosis (a natural process of self-destruction in certain cells) or other cell mechanisms. As the chondrocytes and cartilage matrix get older, the tissue ages, making it more likely to degenerate.

Cartilage is 65 to 80% water. Collagen, proteoglycans, and chondrocytes are also components of cartilage:

• collagen - fibrous proteins that are the building blocks of skin, tendon, bone, and other connective tissues
• proteoglycans - made up of proteins and sugars, strands interweave with collagens and form a mesh-like tissue
• chondrocytes - cells that produce cartilage and help it stay healthy as it grows

With aging, the water content of the cartilage increases and the protein makeup of cartilage degenerates. Collagen decreases in quantity with osteoarthritis. Some research has suggested that oxidative stress leads to chondrocyte aging and cartilage aging, and may be a possible cause of osteoarthritis development. Oxidative stress is defined as heightened free radical activity. Free radicals are molecules in the body that have become unstable due to the loss of an electron. Dietary antioxidants help the body fight oxidative stress.

Bottom Line

Aging is not the direct cause of osteoarthritis. However, certain cellular processes that occur during aging may contribute to the development of osteoarthritis in some people. The risk of developing osteoarthritis increases with age.

_Sources:

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_{Aging, articular cartilage chondrocyte senescence and osteoarthritis. Biogerontology. 2002;3(5):257-64. Martin JA, Buckwalter JA.
http://www.ncbi.nlm.nih.gov/pubmed/12237562}

_{Aging Theories of Primary Osteoarthritis: From Epidemiology to Molecular Biology. Rejuvenation Research. 2004, Vol.7 Number 2. Aigner T, Rose J, Martin J, Buckwalter J.
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_{Chondrocyte senescence, joint loading and osteoarthritis. Clinical Orthopaedics and Related Research. 2004 October (427 Suppl). Martin JA, Brown TD, Heiner AD, Buckwalter JA.
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