Analysis of differential growth of the right and the left leg

In spite of well documented standards for length and annual growth rates of the femur and tibia, there is little information on short term longitudinal bone growth. We investigated differential growth dynamics of the lower leg in 10 children, aged 6:3 to 14:2 years, by knemometry, a novel and non-invasive technique of accurate lower leg length measurement with a technical error of 0.09 to 0.16 mm. Mini growth spurts were detectable in 7 of the children and occurred synchroneously in both legs. Approximately half of the variance of the weekly lower leg length increments could be attributed to synchrony of leg length increments, but a significant amount of residual variance remained which exceeded the technical error of the measurements. Run-analysis of the individual series of right vs. left differences of the weekly lower leg length increments provided evidence for alternating periods of overgrowth of one leg compared to the contralateral side in 5 out of the 10 children. We concluded that there is suggestive evidence of partial independence of lower leg growth in the short term.