MRI tracks connection between obesity and knee cartilage

August 11, 2009

Has the sight of a morbidly obese person making his or her way down a supermarket aisle ever led you to wonder what all that weight is doing to the person’s knees? Data from a study supported by the National Institute on Aging indicates it’s probably doing a lot of cartilage damage.

Has the sight of a morbidly obese person making his or her way down a supermarket aisle ever led you to wonder what all that weight is doing to the person’s knees? Data from a study supported by the National Institute on Aging indicates it’s probably doing a lot of cartilage damage.

“As obesity is one of the few established risk factors for osteoarthritis, it is not surprising that obesity may also precede and predict rapid cartilage loss,” said principal investigator Dr. Frank Roemer, an associate professor of radiology at Boston University.

Roemer and colleagues at research institutions in the U.S. and Germany assessed 336 patients from the Multicenter Osteoarthritis Study, a prospective trial that has enrolled more than three thousand subjects either at risk for osteoarthritis or who have been diagnosed with the condition. Their review included 347 knees with minimal or no baseline cartilage damage at MRI. Nearly 70% of these patients were women with an average body mass index of 29.5 (the Centers for Disease Control and Prevention identifies that number as on the line between overweight and obese for adults).

Over a 30-month period, 20.2% of patients in the study experienced slow cartilage loss while 5.8% showed rapid cartilage loss of the knee. According to study findings, baseline cartilage damage, tears and meniscal injuries, severe lesions, and high BMI accounted for the top risk factors contributing to rapid cartilage loss. Predictive factors also included synovitis and effusion.

Excess body weight, however, was significantly associated with an increased risk of rapid cartilage loss. Each BMI unit increase accounted for an 11% increase in the chance of rapid cartilage loss. No other demographic factors, including age, sex, and ethnicity, were associated with rapid cartilage loss. Findings of the study appeared in the August issue of Radiology.

The investigators isolated demographic and MRI-based risk factors for progressive cartilage loss. Increased baseline BMI, however, was the only non-MRI-based predictor identified, said Roemer, who is also codirector of Boston University’s Quantitative Imaging Center.

According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, nearly 30 million people in the U.S. suffer from the slow cartilage loss that characterizes osteoarthritis. Although the condition develops slowly, a number of patients may experience fast disease progression. Unfortunately for these patients, hardly any signs of the disease appear at first diagnosis. Identifying risk factors is thus the best way to prevent the condition and its disabling consequences, Roemer said.

“Weight loss is probably the most important factor to slow disease progression.”