Regular exercise has enormous benefits for health. Most
importantly, it will reduce the risk of heart attack, stroke, and
premature death. And if that's not enough for you, consider the
many studies that link physical activity to protection against
diabetes, obesity, high blood pressure, osteoporosis and
fractures, depression, insomnia, dementia, colon cancer, breast
cancer, and possibly prostate cancer.
Despite all these benefits, only about a third of American adults
get the exercise they need. Couch potatoes have many excuses to
explain their sedentary ways. Lack of time is the most common,
and the belief that exercise is too hard is a close second. But
since moderate exercise that can be built into daily life is all
it takes to promote health, neither excuse is very convincing.
Another common excuse is a little harder to dispel. It's the
belief that exercise causes arthritis. Even if it were true, it
might be wise to accept aching knees as the price for a healthy
heart, brain, and metabolism. But studies show that exercise can
be safe for joints, both in older, overweight folks and in
The knees of Framingham
In 1948, more than 5,200 residents of Framingham, Mass.,
volunteered for the Framingham Heart Study, which has produced
major insights into the causes of heart attack and stroke. In
1971, scientists began a new study of the children of the
original volunteers and the spouses of those children. Between
1993 and 1994, 1,279 members of the Framingham Offspring Cohort
enrolled in a study of exercise and arthritis. Their average age
All the volunteers were free of arthritis when the study began.
Each answered detailed questions about their patterns of
exercise, including walking, jogging, being active enough to work
up a sweat, and their overall exercise level. All the people
provided information about knee injuries and symptoms of knee
pain and stiffness. In addition, all the volunteers were weighed
and measured, and they each had a full series of knee x-rays.
Between 2002 and 2005, the subjects answered the same questions
about knee pain and injury, and the x-rays were repeated. All the
x-rays were independently evaluated by two experts who had no
knowledge of the subjects' exercise histories.
When the results were tallied, the researchers found no link
between exercise and arthritis of the knee. The most active
people had the same risk of arthritis as the least active, both
in terms of symptoms and x-ray abnormalities. Exercise was as
friendly to the knees of joggers as walkers, even though jogging
subjects the lower body to much higher impact and stress than
walking. And even though obesity is an independent risk factor
for arthritis, physically active overweight members of the study
group fared just as well as their slim peers.
Although the Framingham study goes a long way toward dispelling
the idea that exercise causes arthritis, it did not confirm a
fond hope of exercise enthusiasts. Osteoarthritis begins when the
cartilage that cushions the joints begins to wear away. Because
cartilage does not have its own blood supply, it must get its
nutrients from the joint fluid that bathes it. Exercise
compresses joints, forcing more nutrient-rich fluid into
cartilage. Perhaps, then, repetitive exercise is good
The Framingham study did not find any protection, but a high-tech
investigation from Australia did. Researchers studied 297 men and
women who were between the ages of 40 and 69 when the study began
in the early 1990s. All were healthy, and none had histories of
knee injuries or disease. The volunteers were weighed and
measured, and they provided detailed information about their
exercise habits and joint symptoms. The evaluations were repeated
between 2003 and 2004, and each subject had a knee MRI. The
results showed that people who performed the most vigorous
weight-bearing exercise had the thickest, healthiest knee
The Framingham study is important because it evaluated a group of
ordinary people — middle-aged, often overweight, and not overly
athletic, just like many of us. But a 2008 study that compared
284 dedicated runners with 156 nonrunners also found little
evidence that exercise causes arthritis. After a remarkably long
21-year follow-up period, the runners experienced significantly
less musculoskeletal disability than did their less active peers
— and the runners also enjoyed a 39% lower mortality rate.
The research is impressive, and it confirms earlier studies.
Former varsity runners, for example, are no more likely to
develop arthritis in their legs than former college swimmers, and
champion runners are no more likely to end up with arthritic hips
Exercise as therapy?
Exercise is often prescribed for patients with arthritis.
Exercise may be safe for healthy joints — but is it also safe for
In 2005, British researchers evaluated 13 randomized clinical
trials that compared walking, muscle-strengthening exercises, and
conventional therapy without exercise in patients with
osteoarthritis of the knee. Both walking and muscle-strengthening
were safe and effective, reducing pain and disability. And in
2006 and 2007, scientists in the Netherlands and the U.K.
reported that graded exercise programs are safe and effective for
patients with arthritis of the hip or knee.
Healthy body, healthy joints
Exercise is good for health. Still, it can have side effects. To
prevent problems, be sure your general health is good; older
people and patients with heart disease, hypertension, diabetes,
or other significant problems should get medical clearance. And
all of us should get in shape gradually. Above all, listen to
your body as you exercise your way to health, and be sure to
report any signs of discord to your doctor.
Warming up and cooling down will help protect your heart and your
joints. Stretching exercises, good shoes, and good technique will
also reduce your risk of musculoskeletal injuries. With these
simple precautions and a dose of common sense, exercise will be
safe for your joints.