To establish the diagnostic criteria for hip joint effusion, the normal wid
th of the anterior hip synovial recess in children and the difference betwe
en both hips of the same child were examined in this study. Eight kindergar
ten schools were randomly selected for study in Kaohsiung City. The width o
f anterior hip synovial recess of 1,568 hips in 784 children (421 boys, 363
girls) was measured by ultrasound scanner with 7.5-MHz linear probe. The a
ge of children ranged from 2.5 to 6.6 years old. During measurement, the ch
ildren were put in supine position with hips and knees in extension and pat
ella facing up. The results revealed that the mean width of the anterior sy
novial recess was 7.29 +/- 1.15 mm. Linens correlation of the width of syno
vial recess to age and height was disclosed and expressed as follows: width
(millimeters) equal to 6.52 + 0.013 x age (months), or width (millimeters)
equal to 3.97 + 0.030 x height (centimeters). The mean difference between
both hips of the same child was 0.611 +/- 0.523 mm, and the difference was
independent from the factors of age, gender, height, or weight (p > 0.05).
Ninety-five percent of the differences should be less than or equal to 1.46
mm, so that if the difference between hips is >1.46 mm, hip joint effusion
should be suspected.