Glutei

Your glutus maximus is, surprisingly, relaxed when you are standing. However, when rising from sitting or stooped position it is engaged.  There’s a cross stitch arrangement of nerves in this area of the body I had not accounted for.

The S.I joint remains for me the dodgy hinge on a cupboard, that threatens to drop the door onto your forehead someday if you’re unlucky. The pesky might of mechanics within these parts!