The article describes an approach to measure child growth using a coordinate measuring arm. For this purpose, a test set up has been built to measure the lower leg length directly on the knee surface and with the help of a plate. The use of the plate resulted in the distribution of pressure on the surface to be measured. Based on the results, the LLV (a lower leg growth velocity) was determined and studies were carried out to estimate the uncertainty of this factor. The obtained LLV results at 0.4 mm/week, correspond to the results of studies conducted on specialist test set-ups for knemometric measures described in the literature. The obtained results also allow recognizing periods of good health and bad health of the child.