Relationships Between Standing Frontal-Plane Knee Alignment and Dynamic Knee Joint Loading During Walking and Jogging in Youth Who Are Obese

Background. Youth who are obese have high risk of poor knee health and cartilage damage. Understanding factors which may affect knee health in youth who are obese is critical for preservation of knee integrity and function. Objective. This study compared standing frontal-plane knee alignment and knee loading patterns between youth who are obese and those of healthy weight and determine the association between knee alignment and knee loading patterns during walking and jogging. Design. This study used a cross-sectional matched pair design. Methods. Twenty youth who were obese and 20 youth who were healthy-weight (ages 11-18 years) were recruited. Three-dimensional motion analysis quantified standing frontal-plane knee alignment as well as frontal-and sagittal-plane knee moments during walking and jogging. Paired t-tests, multiple analysis of covariance, and Spearman's rank correlation coefficients were used for analysis. Results. The youth who were obese demonstrated greater knee valgus in standing (P = 0.02), lower normalized peak external knee adduction moments during walking (P = 0.003), and greater normalized peak external knee extension moments during jogging (P = 0.003) compared with the youth who were healthy-weight. Standing knee alignment did not correlate with knee moments in the youth who were obese. Limitations. Results are limited to small, homogeneous cohorts. The standing alignment methodology is not validated in this population and may limit interpretation of results. Conclusion. Youth who are obese stand in more knee valgus and have altered knee loading patterns during walking and jogging compared with youth who are healthy-weight. Frontal-plane knee alignment does not correlate with frontal-plane knee loading patterns in youth who are obese. A better understanding of other mechanisms related to joint loading in youth who are obese is necessary to maintain long-term joint integrity in this population.