Sugary soft drink consumption contributes not only to weight gain, but also may play a role in the progression of knee osteoarthritis, especially in men, according to new research findings presented this week at the American College of Rheumatology Annual Meeting in Washington, D.C.

Knee osteoarthritis is caused by cartilage breakdown in the knee joint. Factors that increase the risk of knee osteoarthritis include obesity, age, prior injury to the knee, extreme stress to the joints, and family history. In 2005, 27 million Americans suffered from osteoarthritis, and one in two people will have symptomatic knee arthritis by age 85.

Researchers at Brigham and Women's Hospital and Tufts Medical Center in Boston, and Brown University in Providence, R.I., looked at data on 2,149 participants in a multicenter osteoarthritis study. Participants were determined to have knee OA by X-ray. At the beginning of the study, each participant's soft-drink consumption, not including sugar-free drinks was measured using a Food Frequency Questionnaire. The researcher followed up with the participants 12, 24, 36 and 48 months later to track their OA progression as measured by joint space change in their medial knee compartments. Body mass index (also called BMI) was also measured and tracked and data for men and women were analyzed separately.

After controlling for BMI and other factors that may contribute to knee OA, men who consumed more soft drinks per week had worse knee OA progression. The joint space became narrower by an average of 0.29 millimeters in men who drank no soft drinks to 0.59 millimeters in men who drank more than five soft drinks a week. Interestingly, men with lower BMI, less than 27.5 kg/m2, showed more knee OA progression with increased soft-drink consumption than men who had higher BMI scores. By contrast, only women in the lowest BMI segment of the study, less than 27.3kg/m2, showed an association between more soft-drink consumption and knee OA progression.

The researchers concluded that men who drink progressively more soft drinks each week may see their knee OA worsen progressively as well. "Little is known about the course of disability over time in patients with osteoarthritis," says Bing Lu, MD, DrPh, the lead investigator in the study. "This study may offer the potential to identify a modifiable dietary risk factor for disease progression, enable evaluation of prevailing recommendations of healthy diet, and thus have potential public health implications."

It is unclear whether this problem is due to high-calorie soft drinks leading to excess weight burdening knees, or if there are other ingredients in soft drinks that contribute to OA progression.

Funding for this study was provided by the National Institutes of Health. Private funding partners include Pfizer, Inc.; Novartis Pharmaceuticals Corporation; Merck Research Laboratories; and GlaxoSmithKline.