piriformis or SI joint pain?

interestingly, the piriformis not only stabilizes the femur, its the key muscle responsible for the lateral rotation of the hip joint, meaning it's the muscle that allows us to open the groin and make ourselves vulnerable. i say interesting, because of how chronic we, the western population as a statistical pool, go into rigid spasm, locking down the front by seizing up in the back instead... humans. looking one way while doing another since, um, forever...

here's the best discussion i've come across on the guiding features that distinguish SI joint pain from piriformis entrapment of the sciatic... Piriformis or SI Joint Pain? by a Certified Advanced Rolfer...