Purpose: The aim of the study was to establish normal reference standards for the appearance of the femoral head ossification center according to age, sex and gestational age.

Material and Methods: Sonographic examination of the hip was performed in 1800 healthy Indian and Israeli infants (900 each) aged 2 to 24 weeks. There was an equal number of males and females. A single physician performed all examinations in each country. For each infant, we recorded sex, date of birth, gestational age at birth (weeks), date of ultrasound examination, age at examination (weeks), and presence or absence of the femoral head ossification center on sonographic examination. All data were collected in a Microsoft Excell file and submitted for independent statistical analysis using paired Fisher exact test, chi-square test, and a NOVA test.

Results: The ossification center was noted in the second week of life in the Israeli infants and at 8 weeks in the Indian infants. By 20 weeks, however, it was noted in 81% or more of the Indian infants but only 22–74% of the Israeli ones. In both groups between 20 to 24 weeks of age the ossification center was noted in more than 90% of the infants.

Conclusions: Knowledge of the normal sonographic appearance of the femoral head ossification center by age and ethnicity will help clinicians in the diagnosis and treatment of hip disorders.