Type of Sacroiliac joints in pelvis are

The pelvic bones are joined by four aiculations (two pairs): Two cailaginous symphyseal joints: the sacrococcygeal joint and the symphysis pubis. These joints are surrounded by strong ligaments anteriorly and posteriorly, which are responsive to the effect of relaxin and facilitate paurition. Two synol joints: the sacroiliac joints. These joints are stabilized by the sacroiliac ligaments, the iliolumbar ligament, the lateral lumbosacral ligament, the sacrotuberous ligament, and the sacrospinous ligament.Reference: Berek and Novak's Gynecology; 14th edition; Chapter 5; Anatomy and Embryology