l 394 knees studied, 90 showed disease progression. Weight gain did have a significant impact. For each 2-unit increase in BMI, researchers found an 8 percent increase in the risk of disease progression. However, this effect was limited to knees in the moderately malaligned legs. In neutrally aligned legs on the one end of the spectrum and severely maligned legs on the other, body weight had no measurable effect on the risk of OA progression. "The effect of BMI on progression was different at different levels of alignment, with the risk being much greater for limbs with moderate malalignment," affirms the study's author, David T. Felson, M.D.

Why would the impact of body weight on knee OA be restricted to legs where malalignment was moderate? Dr. Felson offers possible reasons. In patients with severe malalignment, the extreme stress already placed on local cartilage may be the only risk factor required for continued structural deterioration. In patients with neutrally aligned limbs, the increased joint loading that accompanies increased body weight would be distributed across much of the joint surface, thus protecting against further damage. Since moderate alignment increases the stress on cartilage, the addition of excess weight effectively works to aggravate the cartilage damage. For these patients, losing weight might relieve the stress and considerably slow disease progression.

"Our findings, which need to be confirmed in other studies, suggest that prevention and treatment efforts for obesity and knee OA could be efficiently targeted to those subjects with moderate malalignment," Dr. Felson concludes. "These findings may have broad implications not just for the effect of body weight on OA, but for other risk factors that affect joint loading."

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Contact: Amy Molnar
amolnar@wiley.com
John Wiley & Sons, Inc.
2-Dec-2004

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