Which appendicular joint firmly attaches the axial skeleton to the pelvic girdle?

The Sacroiliac joint is the appendicular joint that firmly attaches the axial skeleton to the pelvic girdle. The Sacroiliac joint or SI joint is the joint between the Sacrum (large, triangular bone at the base of the spine) and Ilium (largest part of the hip bone) bones of the pelvis, which are connected by strong ligaments.  

Cuz i said so. which gives it to b