Dorsal sacroiliac ligaments

Always much stronger than the ventral sacroiliac ligament, the dorsal sacroiliac ligament (Ligamenta sacroiliaca interossea) is subdividable into two parts, a short and a long one, that are often described as two distinct ligaments (Ligamenta sacroiliaca dorsalia) but between which it is difficult to make a demarcation.

The short part is particularly developed in Men, Carnivorous and Glires. It is made of solid fibrous beams that attach themselves dorsally to the auricular surface of the ilium bone as well as the part near the dorsocranial iliac spine, sometimes dorsocaudal (Dogs) and go to the border of the sacrum, on the part that corresponds to the first transverse sacral processes.

The long part appears on the ilium dorsocaudally to the short part, to which it is united. It is ended in Men, Carnivorous and Pigs on the last sacral transverse processes; it even reaches the first coccygean vertebrae in Men but is attached only on the second sacral vertebra in Rabbits. In Ungulates, it gets in continuity with  the sacral attach of the sacrosciatic ligament. In Ruminants and Equidae, it extends is stretching considerably annexing a great part of the sacrosciatic ligament, in order to cover the spinal muscles and to take a very solid attach on the main part of the median sacral crest. 

This solid mean of contention limits the tilting movements of the ilium on the sacrum and interlocks even more tightly the pelvis to the vertebral column. In these animals, especially in Equidae. The dorsal sacroiliac ligament is therefore made of a funicular part, spread from the angle of the rump to the median sacral crest, and of a membranous part that goes from the ventral border of the rump to the lateral border of the sacrum and of the first coccygean vertebrae, covering the spinal muscles.