Sacro-iliac joint problems are of course the "secret" cause. Good review of S-I joint dysfunction but some about the sacrum rotation issues are only clear if you understood what you were reading from before. If you are in treatment, this book will help follow up what is being done which I imagine is how the compilation of info came about. It would be much harder to follow without have received PT or be in therapy. I would not suggest you try the adjustments by another person pulling on your leg unless a therapist actually shows that person what to do. The exercices at the back are good, in stages of difficulty and are S-I joint oriented not just back which are different as some back exercises can only be done with a stable pelvis where S-I joint dysfunction causes instability. Worthwhile as an adjuct but not a stand alone book.