Pelvis and Perineum
To understand the supportive anatomical structures of the pelvis it is necessary to see the ligaments, as well. Viewing the pelvis from the anterior-posterior orientation, the iliolumbar and anterior sacroiliac ligaments can be observed. The iliolumbar ligament, 
as it's name implies, connect the lower lumbar spine to the ilium at the iliac crest and the inner concave surface of the iliac fossa. The anterior sacroiliac ligament 
connects the sacrum to the ilium in the same manner. The sacrotuberous ligament, 
sacrospinous ligament 
and the symphysis pubis 
can also be seen in this view. The symphysis pubis is a band of fibers that connects the two bones of the pubis.
The sacrotuberous and sacrospinous ligaments are best observed on a lateral view. The sacrotuberous ligament 
is a cartilaginous attachment of the sacrum to the ischial tuberosity. In the same respect, the sacrospinous ligament 
connects the sacrum to the ischial spine.
Changing our view from a lateral to a posterior, the iliolumbar ligament 
can be seen and the posterior sacroiliac ligaments 
becomes apparent. The sacroiliac ligament is a strong interosseous connection between the sacrum and ilium on the posterior surface. The sacrospinous 
and sacrotuberous ligaments 
are seen here, as well. All of these ligaments are supportive and connective in nature and serve to stabilize the muscles and organs within the pelvic girdle.