Assessment of the usefulness of weekly knemometric measurements in growth studies

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.