Couch potatoes and gym rats have one thing in common. Both are at higher risk of osteoarthritis.
Researchers say getting too much exercise — or getting too little – can cause the early degeneration of knee cartilage, according to a new study presented at the annual meeting of the Radiological Society of North America .
Scientists at the University of California in San Francisco looked at changes in knee cartilage in over 200 middle-aged adults. Using magnetic resonance imaging (MRI) and a measurement known as T2 relaxation times, they tracked the early degenerative of knee cartilage over a four year period.
They found that strenuous exercise, such as running or tennis, and a lack of physical activity both appear to cause damage to knee cartilage.
“This study seems to suggest that people should do things in moderation,” said Wilson Lin, a research fellow and medical student at UCSF. “You want to exercise the knee, but you don’t want to stress the knee in such a way that would be detrimental. If [they] wanted to run marathons and work out several times a week, I would present them with the evidence that this could be harmful.”
The UCSF team had previously found an association between exercise and cartilage degeneration. But that study focused only on one point in time, and the degeneration caused by a lack of exercise didn’t come to light until the latest research.
“When we compared the scores among groups, we found an accelerated progression of T2 relaxation times in those who were the most physically active,” said Thomas Link, MD, professor of radiology and chief of musculoskeletal imaging at UCSF. “Those who had very low levels of activity also had accelerated progression of T2 values. This suggests that there may be an optimal level of physical activity to preserve the cartilage.”
The 205 participants, age 45 to 60, were at high risk for knee osteoarthritis because of family history, obesity, or a history of knee injury or replacement surgery. They were enrolled in the Osteoarthritis Initiative, a nationwide study funded by the National Institutes of Health on the prevention and treatment of knee osteoarthritis.
Those who participated frequently in high-impact activities, such as running, appeared to develop more degenerated knee cartilage and were potentially at higher risk for the development of osteoarthritis.
And though the relationship between physical activity and the evolution of osteoarthritis is unclear, the study revealed the potential of T2 relaxation time measurements as an early indicator of cartilage damage.
“Standard MRI shows cartilage defects that are irreversible,” said Dr. Link. “The exciting thing about the new cartilage T2 measurements is that they give us information on a biochemical level, thus potentially detecting changes at an earlier stage when they may still be reversible.”
People who have a higher risk for osteoarthritis can reduce their risk for cartilage degeneration by maintaining a healthy weight and avoiding risky activities and strenuous, high-impact exercise, according to Dr. Link.
“Lower impact sports, such as walking or swimming, are likely more beneficial than higher impact sports, such as running or tennis, in individuals at risk for osteoarthritis,” he said.
Osteoarthritis is the most common form of arthritis, and affects more than 27 million Americans and over 100 million people worldwide. Osteoarthritis mainly impacts the hands, knees, and hips, and is the leading cause of disability in the U.S.
According to the Centers for Disease Control and Prevention, nearly one in every two people in the U.S. may develop knee osteoarthritis by age 85. By 2030, an estimated 67 million Americans over the age of 18 are projected to have physician-diagnosed arthritis.