A novel miniaturization of knemometry for accurate measurements of the lower leg length in prematures, newborns and infants (mini-knemometry), is presented. The study was performed in four healthy neonates, born at term, and one infant, born in the 34th week of gestation, measured daily for periods of 40 days; and in two monozygotic healthy twin sisters, born in the 32nd week of gestation, measured daily for periods of 58 days. Each of the 316 measurements consisted of four independent subsequent estimations of the distance between heel and knee, which are grasped by two metallic holders under light compression of 2.0-3.0 N. After an initial training of 1 week the technical error is 144 microns. Lower leg growth is non-linear (p < 0.001) with periods of stunted, and periods of accelerated, growth velocity.