well usually those verts down "there" fuse together to become your coccyx and your sacrum....and i don't think they are adjustable....but maybe they are....or maybe yours didn't fuse together. my mom has always had problems in that area...especially after giving birth to 3 kids. my sister did too...but she went to physical therapy...and just hit up some very basic hip mobility stuff and anterior core strengthening stuff....problem solved.

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