I received your question about left SI pain. I’d love to share a couple of thoughts to answer your questions and try to clear a few things up.
On the topic of left SI torsion and compression, let me clarify a couple of points:
On a very general level (for the non-pathological left hip patient), right SI pain can be described as torsion and distraction and the left SI can be described as torsion and compression. But if you look closely at the pathomechanics of both right and left SI joint pain, its a little more complicated than that. The right SI joint is experiencing a right rotated torsion as the sacrum rotates right on a right oblique axis, which gaps the posterior aspect of the right SI joint. If the left hip becomes so pathological that lumbo-pelvic and hip position prevents the ability to position into left AF IR, then the left SI joint can develop a pathology. When the left hip does not properly position itself or properly function, then the left SI joint shifts into pathological mode. This is notable for a right rotated torsion across the joint as the sacrum rotates away from the left illium on the same right oblique axis, which gaps the anterior aspect of the left SI joint. So in actuality, both joints experience torsion and distraction, but the direction of sacral movement away from each illium yields a different area of joint separation (the back on the right and the front on the left).
James Anderson, MPT, PRC