Preventing Osteoarthritis: How Much Exercise is Just Right?

Study Shows Too Little or Too Much Physical Activity Increases Loss of Knee Cartilage

By Jason Bardi

Very high and very low levels of physical activity can both accelerate the degeneration of knee cartilage in middle-aged adults, according to a new study presented this week by UCSF researchers.

Thomas M. Link, MD, PhD

Thomas M. Link, MD, PhD

During the annual meeting of the Radiological Society of North America (RSNA) in Chicago, Thomas M. Link, MD, PhD, chief of the Musculoskeletal Imaging Section in UCSF’s Department of Radiology and Biomedical Imaging described a study expanding on earlier work that showed an association between physical activity and cartilage degeneration.

Nearly one in every two people in the U.S. may develop knee osteoarthritis by age 85, according to the Centers for Disease Control and Prevention. By 2030, an estimated 67 million Americans over the age of 18 are projected to have physician-diagnosed arthritis.

In the new study, Link and his colleagues looked at changes in knee cartilage among a group of 205 middle-aged adults over a four-year period, taking magnetic resonance imaging (MRI)-based measurements every two years to track early degenerative changes to the cartilage in their knees over time.

The patients were all part of the Osteoarthritis Initiative, an international collaboration working on the prevention and treatment of knee osteoarthritis that is coordinated by UCSF and funded by the National Institutes of Health. They answered questionnaires yearly over four years to correlate their exercise levels with the MRI measurements. 

What the researchers found is that the patients who were the most physically active showed accelerated degeneration of knee cartilage over time. Participating frequently in high-impact activities, such as running multiple hours per week, appeared to be associated with a higher risk for development of osteoarthritis. Those who had very low levels of activity also had accelerated degeneration and higher risk.

MRI images of the right knees of middle-aged men who engage in moderate and very low levels of physical activity. A measure called the T2 relaxation time shows increased degeneration in the knee cartilage of the low-activity patient over four years (lower row), while the individual with moderate activity shows little change over four years (upper row).

“Based on these results, moderate physical activity levels appear most beneficial to prevent cartilage degeneration in patients at risk for osteoarthritis,” said 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.”

At the early stages of osteoarthritis, cartilage changes are reversible, and people who are at higher risk for osteoarthritis because of knee injuries, surgery, a family history of total joint replacement or obesity can reduce their risk for cartilage degeneration by maintaining a healthy weight and avoiding risky activities and strenuous, high-impact exercise, Link said.

“Physical activity is a modifiable lifestyle factor, which may impact cartilage degeneration and thus the evolution of osteoarthritis,” he said.

Primary funding for this study was provided by the Osteoarthritis Initiative, a public-private partnership comprised of five NIH contracts (#N01-AR-2-2258; #N01-AR-2-2259; #N01-AR-2-2260; #N01-AR-2-2261; and #N01-AR-2-2262).

Private funding for the Osteoarthritis Initiative is managed by the Foundation for the National Institutes of Health and includes contributions from Merck Research Laboratories, Novartis Pharmaceuticals Corporation, GlaxoSmithKline and Pfizer, Inc.