Accessory sacro-iliac articulations occur in man in varying percentages according to race, sex, and age.
The articular surfaces may be covered with either hyaline cartilage or fibrocartilage.
The posterior portions of the ilia are less widely separated in pelves presenting the variation than in pelves which are considered to be normal. However, these differences are not sufficient to be of statistical significance.
Roentgenographic examination of the pelvis in the living has shown accessory sacro-iliac facets in one case.