The relationship between short-term changes in weight and lower leg length in children and young adults

As the knemometer is increasingly being used to study changes in lower leg length in conditions associated with weight changes it is important to clearly delineate the relationship between these two variables. Lower leg length and weight were measured in 26 children and nine adults including one pregnant woman. There was a weak but positive relationship between lower leg length and weight fluctuation in children. Daily fluctuations in weight as well as lower leg length were higher in women than men; median lower leg length fluctuation: women, 0.16 mm (P5-0, P95-0.7); men, 0.1 mm (P5-0, P95-0.48) p similar to 0.02, Wilcoxon signed-rank test. Median weight fluctuation: women 0.15 kg (P5-0, P95-0.54); men, 0.1 kg (P5-0, P95-0.5) p = 0.94 (Wilcoxon signed-rank test). Sustained weight gain in pregnancy led to a reduction in lower leg length followed by an increase which was coincident with the appearance of dependent oedema. Lower leg length changes are likely to be positively related to changes in weight when the latter are only modest in magnitude. However, greater sustained increases in weight are likely to have an opposite effect on lower leg length due to direct compression of the lower leg. Due consideration of weight is essential in longitudinal studies of lower leg length changes, especially in conditions which are associated with significant changes in weight.