Comparison of predictive accuracy of knee height equations in children

Knee height can be a proxy for height when standing height cannot be reliably measured. We compared two commonly used equations (Chumlea and Rumapea) that estimate standing height from knee height. We prospectively enrolled 210 children without scoliosis or kyphosis aged 7-12 years (mean age: 10.2 years, 47.6% males) and measured their knee heights and standing heights. A two-tailed T-test was used to compare predicted heights from each of the equations to actual standing height. Chumlea equation was found to be unreliable (p = 0.0376) while Rumapea equation was found to be reliable in estimating standing height (p = 0.878). Additionally, Rumapea equation was also found to be more accurate than Chumlea equation when results were segregated based on gender and race. In conclusion, the Rumapea equation yields more accurate estimates of standing heights than the Chumlea equation in US children aged 7-12 years.