Sometimes the SI Joint is misaligned due to improper sitting ( for men sitting on a large wallet) can greatly affect this joint. Massage /chiro can help to relax the tight pelvic and lower back muscles while guiding the joint into better position. It is a sliding type of joint not a lot if movement in it but the SI nerve that runs thru the pelvis and can cause so much discomfort is about the size of your pinkie so once irritated it takes a bit to settle it down. Good luck nothing worse than the back pelvis pain on top of a hip revision

Self Care Central