The results of ultrasonographic examinations of the patellar height in the knee joints in children was subjected to analysis. The study aimed at the specification of a norm of patellar height in the developmental age, based on the tendon-patellar coefficient (analogous to the radiologic measurement according to Insall and Salvati). The results of ultrasonographic and clinical examinations of 114 knee joints performed in 57 healthy children were used for the study. The average value of the tendon-patellar coefficient was 1.2 and was independent of age or sex. A statistically significant dependence of the coefficient on the popliteal angle was demonstrated, which indirectly proved the dependence of the coefficient on the length of the hamstrings. In our opinion, the use of ultrasonographic tendon-patellar coefficient allows the differentiation of the so-called physiologic shortening of hamstrings from its pathologic form.