Assessment of the usefulness of weekly knemometric measurements in growth studies

Abstract

In 31 healthy children the variability of lower leg length growth over 12 weekly measuring sessions, each consisting of 6 measurements, was assessed with a knemometer. The average SD of 6 measurements was 0.12 mm. In many cases not only a rising trend, but also a zig-zag pattern was observed. The linear regression was not significant (p greater than 0.05) in 1 child. The average (+/- SD) lower leg length velocity (LV) was 0.36 +/- 0.14 mm/week, and the average statural growth velocity 1.27 +/- 0.54 mm/week. The median ratio was 3.3. The range of both velocities was greater than the range of annual height velocities. When LV over the first 6 weeks was compared with LV over the next 6 weeks, a significant difference was found in 5 children. If the effect of growth-promoting or -inhibiting drugs were to be analyzed over such periods, a difference of 0.37 mm/week over two 6-week-periods would be necessary for significance at a 5% level. This would be equivalent with a statural growth response of at least 6.3 cm/year. In conclusion, short-term knemometric growth response cannot be used as a reliable predictor of long-term statural growth response.