The sacroiliac joints reside concerning the sacrum (the tailbone section of the spinal column) as well as notable wing-like iliac bones that form the pelvic girdle. There's two SI joints, 1 around the left and a single on the right (highlighted in purple while in the picture above), and together https://www.theorthopaedicandpainpractice.com/service/hip-groin-pain/