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ACSM'S Health & Fitness Journal:
doi: 10.1249/01.FIT.0000252524.82735.b4
Departments: You Asked For It: Question Authority

You Asked For It: Question Authority

Nieman, David C. Dr.PH, FACSM

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David C. Nieman, Dr.P.H., FACSM, is professor and director of the Human Performance Laboratory, Appalachian State University, in Boone, North Carolina, an active researcher, and author of several textbooks on health and fitness. Email your questions to niemandc@appstate.edu.

Q: I am 43 years old, and several of my older friends have been told by their doctors that they have osteoarthritis. I'm worried. What can I do to prevent osteoarthritis?

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A: There is much that you can do to prevent osteoarthritis. No cure for arthritis exists, so growing emphasis is being placed by the U.S. Centers for Disease Control and Prevention (CDC) on prevention.

Your concern about arthritis is well founded. Arthritis affects 43 million Americans (one in five adults and half of the elderly) and is expected to impact about 61 million by the year 2025. The Arthritis Foundation reports that another 23 million adults currently have arthritis but have not been doctor diagnosed (see www.arthritis.org). Arthritis is the number one cause of disability in America and limits everyday activities such as dressing, climbing stairs, getting in and out of bed, and walking.

Arthritis means joint inflammation and refers to more than 100 different conditions that affect your joints and other body parts. The most common type of arthritis is osteoarthritis, a process that starts when joint cartilage breaks down, sometimes eroding entirely to leave a highly inflamed, bone-on-bone joint (Figure 1).

Figure 1
Figure 1
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Do your best to control the risk factors for arthritis-this is the key to prevention. According to the CDC (www.cdc.gov/arthritis), the factors listed below increase the risk of arthritis. Some of these risk factors are modifiable, whereas others are not.

Nonmodifiable risk factors include the following:

* Age. The risk of developing most types of arthritis increases with age.

* Sex. Arthritis is more common in women, accounting for 60% of all cases. Gout is more common in men.

* Genetic. Genes have been identified that are associated with a higher risk of certain types of arthritis, such as rheumatoid arthritis and lupus.

Modifiable risk factors include the following:

* Overweight and obesity. Excess weight can contribute to both the onset and progression of knee osteoarthritis.

* Joint injuries. Damage to a joint can contribute to the development of osteoarthritis of that joint.

* Infection. Many microbial agents can infect joints and potentially cause the development of various forms of arthritis.

* Occupation. Certain occupations involving repetitive knee bending are associated with osteoarthritis of the knee.

If you are overweight, a key strategy in arthritis prevention is to achieve and then maintain normal weight throughout adulthood. Obesity increases the risk of osteoarthritis 4 to 10 times more than that of normal weight adults (1). Obesity produces changes in the joint cartilage cells that decrease their ability to keep the joint lined with a thick, smooth layer of cartilage. Over time, the cartilage in the joints of overweight individuals breaks down, sometimes eroding entirely to leave a bone-on-bone joint. The "National Arthritis Action Plan: A Public Health Strategy" organized by the Arthritis Foundation and the CDC has identified weight management as a key strategy for the primary prevention of knee osteoarthritis in the general population (www.arthritis.org).

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Beware of claims that certain types of foods cause arthritis. The link between diet and arthritis is still being investigated. Some studies suggest that higher intakes of red meat and total protein and lower intakes of fruit, vegetables, and vitamin C are associated with an increased risk of arthritis and that the Mediterranean-type diet may have protective effects, but much more research is needed before a consensus can be established (2).

Another important preventive strategy is regular physical activity to attain aerobic and muscular fitness. There is growing evidence that individuals who stay lean and fit as they grow older are at a much lower risk for the development of osteoarthritis compared with their obese and unfit counterparts (1, 3). Thigh muscle weakness has emerged as a predictor of future knee osteoarthritis, so keep your legs strong through daily exercise (e.g., brisk walking up and down hills and stairs) (3).

You may have heard that osteoarthritis is a "wear-and-tear" disease, and fear that high amounts of walking, jogging, cycling, and other forms of exercise will thin out the cartilage in your knee and hip joints. For most people with healthy joints, this simply is not true. Data from the Aerobics Center Longitudinal Study indicate that regular physical activity reduces the risk of hip and knee osteoarthritis for both men and women (4) (Figure 2).

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Figure 2
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Other studies demonstrate the importance of regular physical activity in lowering your risk of osteoarthritis and that obesity and previous joint injury are the real concerns. For example, a study of 800 men and women in Finland showed that risk of osteoarthritis decreased with increasing hours of recreational physical exercise (5). Another study of more than 5,000 subjects showed that participation in physical activity as an adult did not increase the risk of hip or knee osteoarthritis (6). Among walkers and runners, there was no association between the frequency, pace, or weekly training mileage. Instead, older age, previous joint injury and surgery, and obesity were confirmed as the most important risk factors for knee/hip osteoarthritis.

If your joints are healthy, the cartilage will respond positively to regular exercise and will not thin out. For those who have experienced a traumatic joint injury, however, risk for osteoarthritis is unusually high. In one study, individuals with a prior history of knee injury were eight times more likely than those without injury to develop knee osteoarthritis later in life (7). There also is evidence that risk of knee osteoarthritis is increased in those who kneel or squat for more than 2 hours a day as a part of their work, especially if they are obese or engage in heavy lifting (8).

In summary, normal knee and hip joints (i.e., those without underlying biomechanical problems or prior traumatic injury) respond well to regular physical activity and do not "wear out." Keep your legs strong through daily exercise and keep lean, and your odds of developing arthritis will fade (and not your joint cartilage).

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References

1. Mehrotra, C., T.S. Naimi, M. Serdula, et al. Arthritis, body mass index, and professional advice to lose weight: implications for clinical medicine and public health. American Journal of Preventive Medicine 27:16-21, 2004.

2. Choi, H.K. Dietary risk factors for rheumatic diseases. Current Opinion in Rheumatology 17:141-146, 2005.

3. Bennell, K., and R. Hinman. Exercise as a treatment for osteoarthritis. Current Opinion in Rheumatology 17:634-640, 2005.

4. Rogers, L.Q., C.A. Macera, J.M. Hootman, et al. The association between joint stress from physical activity and self-reported osteoarthritis: an analysis of the Cooper Clinic data. Osteoarthritis Cartilage 10:617-622, 2002.

5. Manninen, P., H. Riihimaki, M. Heliovaara, et al. Physical exercise and risk of severe knee osteoarthritis requiring arthroplasty. Rheumatology (Oxford) 40:432-437, 2001.

6. Hootman, J.M., C.A. Macera, C.G. Helmick, et al. Influence of physical activity-related joint stress on the risk of self-reported hip/knee osteoarthritis: a new method to quantify physical activity. Preventive Medicine 36:636-644, 2003.

7. Sutton, A.J., K.R. Muir, S. Mockett, et al. A case-control study to investigate the relation between low and moderate levels of physical activity and osteoarthritis of the knee using data collected as part of the Allied Dunbar National Fitness Survey. Annals of the Rheumatic Diseases 60:756-764, 2001.

8. Zhang, Y., D.J. Hunter, M.C. Nevitt, et al. Association of squatting with increased prevalence of radiographic tibiofemoral knee osteoarthritis: the Beijing Osteoarthritis Study. Arthritis and Rheumatism 50:1187-1192, 2004.

© 2006 American College of Sports Medicine

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