Obesity Contributes to Rapid Cartilage Loss

A study published in the August issue of Radiology found that obesity is a significant risk factor associated with rapid tibio-femoral cartilage loss. Cartilage damage can occur due to excessive wear and tear, injury, misalignment of the joint, or other factors, including osteoarthritis. In osteoarthritis, the cartilage breaks down and, in severe cases, can completely wear away, leaving the joint without a cushion. The bones rub together, causing further damage, significant pain, and loss of mobility. The best way to prevent or slow cartilage loss and subsequent disability is to identify risk factors early.
 
"We have isolated demographic and MRI-based risk factors for progressive cartilage loss," says the study’s lead author, Frank W. Roemer, MD, an adjunct associate professor at Boston University and codirector of the Quantitative Imaging Center at the department of radiology at Boston University School of Medicine. "Increased baseline body mass index (BMI) was the only non-MRI–based predictor identified."
 
The researchers recruited patients from the Multicenter Osteoarthritis (MOST) Study, a prospective study of 3,026 people, age 50 to 79, at risk for osteoarthritis or with early x-ray evidence of the disease. The study is funded by the National Institute on Aging.
 
Roemer’s study consisted of 347 knees in 336 patients. The patient group was comprised of 65.2% women with a mean age of 61.2 and a mean BMI of 29.5, which is classified as overweight. Recommended BMI typically ranges between 18.5 and 25. Only knees with minimal or no baseline cartilage damage were included. Of 347 knees selected for the study, 20.2% exhibited slow cartilage loss over the 30-month follow up period and 5.8% showed rapid cartilage loss. Rapid cartilage loss was defined by a whole-organ MRI score of at least 5, indicating a large full-thickness loss of 75% in any subregion of the knee during the follow up period.
 
"Osteoarthritis is a slowly progressive disorder, but a minority of patients with hardly any osteoarthritis at first diagnosis exhibit fast disease progression," Roemer says. "So we set out to identify baseline risk factors that might predict rapid cartilage loss in patients with early knee osteoarthritis or at high risk for the disease."
 
The results showed that the top risk factors contributing to rapid cartilage loss were baseline cartilage damage, high BMI, tears or other injury to the meniscus, and severe lesions seen on MRI at the initial exam. Other predictors were synovitis and effusion. Excess weight was significantly associated with an increased risk of rapid cartilage loss. For a one-unit increase in BMI, the odds of rapid cartilage loss increased by 11%. No other demographic factors—including age, sex, and ethnicity—were associated with rapid cartilage loss.
 
"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," Roemer says. "Weight loss is probably the most important factor to slow disease progression."
 
— Source: Radiological Society of North America