A D.O. or a PT OCS will teach him how to move it himself, if it needs to be moved. In older men it usually doesn't move and isn't meant to. If he has a problem with it moving and getting painfully stuck in the wrong spot, the DO or PT will teach him how to correct it and fix it himself. (I think I've only treated maybe 2 men who had actual SI problems.)

And always, always, always; the first thought is to rule out a lumbar spine problem.