Amy:
I feel a little "101" here, but what is the bullet point implications here - I kinda assumed fused = no movement anywhere.  The SIJ might not move much but lose that micromotion and some macromotions get effected. What is that lateral marco motion used for, is probably a better way to ask my  question.
 
Jerry Hesch
Amy, just after I posted it I scrolled through my You tube videos and made the discovery some time ago, just did not recall! So there is another video on same topic with CT scan evidence. Yes fused left sij means no movement in the left SIJ. I do believe that every biomechanical expert would be very surprised to see that a one-sided SIJ fusion significantly restricts pelvic side-glide mobility. Pelvic side glide is not thought to be a pure motion in the sij, but rather very minuimal sij motion and more motion of the lumbar spine and of the hip joints.  Place your hand on the sacrum and try to glide it left and right, tell me what you find. lie the person on their left side and compress the right ilium and spring test it. What do you feel? I will  explain.

Jerry Hesch
The lateral micromotion is a functional motion during gait, lateral weight shift, etc. It of course becomes a macromotion during such movements. The test for this motion is very relevant as some clients have it restricted, yet it is treatable with Hesch Method and it is a preventive model. Side-glided pelvis' even if subtle alter weight bearing throughout the kinetic chain, especially the lower extremities, and of course as you know; will create a distal compensation such as at the occipitoatlantal joint, which in time becomes symptomatic and non responsive to "adjusting the upper cervical spine". Does that answer your question. Micromotion is such a fundamental property of joints like the SIJ, so very relevant to test if one is using terminology such as "joint". Otherwise one is talking about the bony pelvis as it moves on the hips, which is NOT sij motion, despite the popularity thereof. I believed such for many years, but could not ignore the burgeoning research.
 

After the seminar we filmed a PT who has a pathological fusion of one sacroiliac joints. I was amazed to see how significantly this restricted pelvic side-glide tested passively. The SIJ might not move much but lose that micromotion and some macromotions get effected. There are 2 videos, part 1, 2. 
Please copy and paste in browser.
Part 1.
http://www.youtube.com/watch?v=xc1NU7XnmwE
Part 2.
http://www.youtube.com/watch?v=tKYjwilI7Dk

In response to an inquiry re pelvic/sij alignment.
Derek,
I have seen x-rays of "aligned" clients who had surgery and they were not aligned at the symphysis pubis joint and not aligned in the transverse plane.  Tops of iliac crests appear to be symmetrical. a huge problem is the fact that the body can cause asymmetry of the pelvis from joints in the spine, hip, knee, the 26 bones in foot and ankle, all the musculature, even asymmetry of shoulders can pulll on a muscle that connects the shoulder to the ilium; latissimus dorsi. 

Research on x-rays covered in my torsion chapter briefly, positional artifact can affect some of the alignment. Some clients have a developmental asymmetry of the hemipelvis and this can be readily discerned. I am much more concerned about maximizing joint function than "alignment". Asymmetry, visual malalignment guides me to do passive joint testing to confirm or negate possibilities. 

Several pelvic asymmetries look very similar, so the passive mobility testing and ligament testing is crucial to discern.  Further there are advanced patterns that are not taught to Physical Therapists, that PT's cannot find with the traditional testing. It is what it is. It is far more comnplex than what is being propounded, but fortunately for the majority, the presentation is fairly typical such as the Most Common Pattern.  If interested in more you can find more at the Hesch Institute web site.  Snake oil or purple kool aide $$$ dunno but we can be much more thorough in testing and treating and much more honest in the information we give to desperate clients.  It is a choice we (as clinicians) can make.

A dislocation the SIJ is imaged on a ct scan and x-rays (more than one view) whereas the same ct scans and x-rays for "malalignment" does NOT show malalignment in the SIJ.  An elevated iliac crest is NOT indicative of a malalignment in the sacroiliac. Falsely overinterpreted in texts such as Professor Dihlman in Diagnostic Radiology of the Sacroiliac Joint, pp91-99. (Of 
note, Dick DonTigny gave me that book in 1990, the book published in 1980.) He clarifies that functional films such as standing on one leg and then the other cannot be read with a line across the top of the sacrum (ala) and contrasted with one across the top of iliac crests, unless there is a concommitant vertical change in the height of the symphysis pubis. If the vertical symmetry of the pubic changes when you stand on the other foot, AND the iliac and scarl lines
change; then yes a valid case of hypermobility is objectively noted. Simply observing an iliac crest being higher than the other can be a purely muscular phenomen and there are problems of patient positioning when the x-ray or ct is taken which I have detailed in my chapter on sacral torsion. Dihlman goes on to insightfully state on p95, "Functional films only provide information as to whether the displacement (pubic and crest) is mobile or interlocked, or wheteher the pelvic rigidity which developed with the displacement of the sacroiliac joints and the pubic symphysis is complete or incomplete. Such information is important for determining the therapy".  I assure you that any x-ray of iliac crests and SIJ's must include the entirity of the symphysis pubis  and standing on one leg and then the other with fluroscopy imaging or x-ray
imaging or standing CT scan are mandatory. For me, I would never ever let
someone talk me into getting surgery on the basis of uneven iliac crests, unless
that grape kool aide is very, very spiked, rendering me vulnerable. knowledge is
power and carries an ethical responsibility. I invite clinicians to participate
in this public forum.


Jerry Hesch, Hesch Institute