A PORTABLE KNEMOMETER - A TECHNIQUE FOR ASSESSMENT OF SHORT-TERM GROWTH

Knemometry is the technique of choice for short-term growth studies, a s it is the only anthropometric technique available that allows suffic iently accurate measurement of the lower leg (in anatomical terms, the leg) to enable changes in leg length to be detected over as short an interval as a week or less. The portable knemometer, like the Valk kne mometer, essentially consists of two main parts: a rigid metal frame h olding the footplate, measuring ruler and plateau and a moveable chair that moves on frictionless rollers on a track on the base of the fram e. Unlike the Valk knemometer there is a standardized seat position fo r all subjects, making it easier and quicker to use. Assessment of tec hnical error was done using mean coefficient of variation (CV) of lowe r leg length measurements done on the portable knemometer. Comparison of measurements made by two different observers was made by using perc entage reliability. A small PR implies consistency between the two met hods or observers being compared. Measurements from 164 visits were us ed to calculate the machine precision. Mean CV using all four measurem ents was 0.13% and using only three, having discarded the first, was 0 .11%. Given a mean lower leg length of 246.3 mm for the children studi ed this translates to a machine precision of 0.32 mm if all four measu rements are used and 0.27 mm if the last three measurements in the set are used. The mean difference in lower leg length between observers w as 0.11 mm. Percentage reliability between the two observers for the p ortable knemometer was 0.03%. For comparison, PR for standing height a nd sitting height are 0.37% and 0.86% respectively. PR between the Val k and the portable knemometer was 0.04%.