Based on PRI theory, what SI joint would move more in the sagittal plane? And what SI joint would move more in the frontal plane (research says more sagittal plane motion of the right and more frontal/coronal plane motion on the left side)?
Really depends on the patient. We could argue for both but wouldn’t have enough evidence behind it to be objective.
It would make sense that in a Left AIC pattern the innominate moves anterior on the left and posterior on the right – possibly equally in the sagittal plane. And therefore, we see right SI pain patients do well with PRI. Compensation on the left usually is in the transverse plane to accommodate the need for more FA ER which usually results in overactive glute max muscle and left SI pain. Frontal plane orientations and compensation are difficult to assess without fluoroscopy because passive orientation isn’t a reflection of what is moving more or less.