I have to say I have not noticed any real difference in range of motion of the left si joint (the one affected).
However, what is significant and that I failed to mention is that my right hip is moderately arthritic. It is painful and stiff at times. I find yoga and strengthening exercises help manage and minimize this. For my age, 60, I have good rom in it and the supporting muscles are strong from exercise, but internal and external rotation are hindered.
The si pain is in my left lower back. This imbalance in the hips is a causal factor I am sure. The left si joint is probably called upon to be more flexible to compensate for the stiffness in the right hip.
I hope that helps.
Thank you for advising!
Look forward to your reply.