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.
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.
How is osteoarthritis related to aging? Osteoarthritis Information Center. American Federation for Aging Research. Accessed 2/14/2008.
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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.
Chondrocyte senescence, joint loading and osteoarthritis. Clinical Orthopaedics and Related Research. 2004 October (427 Suppl). Martin JA, Brown TD, Heiner AD, Buckwalter JA.