Valgus Knee Alignment, Not Step Width or Toe-Out Cause Reduced Knee Adduction Moment in the Healthy Obese

Obesity is a strong risk factor for knee osteoarthritis (OA) [1], but the mechanism of OA initiation associated with obesity is not clear. Increases in ambulatory knee joint load due to obesity have been implicated as a cause of increased OA incidence, since an increased adduction moment has been associated with the severity and progression of medial compartment OA [2]. However, previous work has not consistently shown increases or decreases in the adduction moment in the obese. Step width and toe-out reduce the adduction moment [3] and are increased in the obese [4], suggesting that the adduction moment could also be reduced in the obese. Furthermore, obesity may be associated with knee malalignment, which may also alter the adduction moment. However, the cumulative effect of these gait alterations on the adduction moment is unclear, given the increased risk of medial knee OA in the obese. Understanding this interaction is important in understanding the link between obesity and knee OA.