From: David A Gabel
Published November 26, 2012 10:01 AM

New Study Reveals the Key to Maintaining Healthy Knees

The human knee is an extremely important joint. It holds the weight of the entire body, provides the strength needed to lift heavy objects, and bends and flexes to give us mobility. Since this crucial joint is under stress at almost all times (except when sitting or lying down), it is susceptible to wear over time. This is especially true for the cartilage which holds together all the bones in the knee. As we age, the knee ages and the cartilage can develop a number of ailments that could potentially prohibit mobility. A new study presented at the annual meeting of the Radiological Society of North America found that both too much and too little physical activity can accelerate the degeneration of knee cartilage in middle-aged adults.

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Knee problems are one of the most common afflictions around the world. In the United States, nearly 50 percent of all people may develop knee osteoarthritis by age 85. It is predicted by the 2030, that an estimated 67 million Americans over age 18 will have physician-diagnosed arthritis.

A previous study from the University of California at San Francisco (UCSF) found the connection between physical activity and cartilage degeneration. The new study from UCSF looked at the correlation over a 4-year period rather than a single point in time using MRI T2 relaxation times to track the evolution of the cartilage deterioration.

"T2 relaxation times generated from MR images allow for analysis of the biochemical and molecular composition of cartilage," said Wilson Lin, B.S., research fellow and medical student at UCSF. "There is increased water mobility in damaged cartilage, and increased water mobility results in increased T2 relaxation time."

Over 200 individuals, age 45-60, were given a questionnaire to record their physical activity. Cartilage at the patella, femur, and tibia of the right knee joint was measured at baseline, two-year and four-year visits.

The results show that frequent running and other high-impact activities appear to be associated with more cartilage degeneration and a higher risk of developing osteoarthritis. However, they also found that people with very low levels of physical activity had accelerated cartilage degeneration, suggesting that there is an optimal level of physical activity to preserve cartilage.

The researchers also stress other factors involved, such as a genetic disposition for osteoarthritis, obesity, or a history of knee injury or surgery. For those people at most risk, it is imperative to maintain a healthy weight and avoid high-impact exercise.

"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.

This study was presented at the annual meeting of the Radiological Society of North America.

Knee image via Shutterstock

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