1. What, exactly, are we repositioning with the 90-90 repositioning techniques?
2. Why are patients ALWAYS in a posterior pelvic tilt when doing the exercises?
3. What about patients who are already in a posterior pelvic tilt (i.e. no butt; they stand / exist in a posterior tilt)?
1. You are repositioning the left coxal bone into extension, adduction and IR, called L AF IR, which actually repositions all 3 bones in the pelvic girdle (2 coxal bones and the sacrum). Of course any change in position to the bones actually will change the position and relationships of all the associated joints and most importantly, all the associated muscles.
2. Not always, but almost always in a posterior pelvic tilt. If all patients started in a neutral sagittal plane position, you could view our positioning as heavily focused on posterior tilting. But since most people are positioned forward on one or both sides, the posterior tilt emphasis is actually a strong effort to pull the pelvis back so the patient moves into a more neutral spine position and to counter the strong neuromuscular extension pattern called the AIC.
3. Patients who stand in a posterior pelvic tilted position with their pelvis translated forward into a sway back kyphotic posture often have a different hamstring:hip flexor (length, tension, strength, tone) ratio because of the lengthening of the hip flexors and the positionally shorter hamstrings. Note that they still could have a forward tilted pelvic position that appears to be in a posterior tilted state (with what may seem like AF EXT and AF IR), but the forward translation of the pelvic girdle is what really brought about the apparent position change.