Eighty knees of 40 musculoskeletally normal infants whose age ranged from 0 to 24 months (average 9.65 months) were ultrasonographically analyzed. The lengths of the patella, patellar ligament - and the Insall-Salvati index, knee being flexed at 30 degrees, were assessed. The angles of the femoral cartilaginous sulcus knee flexed at 0, 30, 60, and 90 degrees were also defined. Patellar length varied from 1.84 to 2.02 cm (mean, 93.3cm; standard deviation, 0.35); patellar ligament length varied from 1.67 to 1.86 (mean, 1.76 cm; standard deviation, 0.25); the Insall-Salvati index varied from 1.04 to 1.13, (mean, 1.09; standard deviation, 0.14); and femoral cartilaginous sulcus angle ranged from 148.7 to 149.3 degrees (average, 148.9 degrees and standard deviation, 6.20). Statistical tests showed no significant difference in the proposed measures according to sex and side (right/left). Moreover, we did not observe significant difference in the femoral cartilaginous sulcus angle with respect to the various degrees of knee flexion. Thus, we conclude that ultrasonography is useful for determining the normal values of the Insall-Salvati index and femoral cartilaginous sulcus angle in infants from 0 to 24 months. Then, we suggest standardization of this imaging procedure for the early diagnosis of deformities, which might impair the knee in infants within this range of age.
