It is important to be aware of the normal anatomy when analysing MR images. However, the anatomical structures are not always visible. The ventral sacroiliac ligament is thus sometimes, but not always visible at MRI.
The MR image (semi-axial T1 FS + Gd.) does not visualise the ventral sacroiliac ligament on the left side, but it is clearly demonstrated on the right side (arrow). The microscopic image is shown for comparison.