Back in September last year I finally had an SI Xray done. They took one film, with me lying flat on my stomach on the table. It was reported in true NHS fashion in two sentences.
"SI Joints: Mild degenerative change with minimal sclerosis, the other bony appearances are within normal limits. Degenerative change involving the level L5/S1 with intervertebral space narrowing."

I asked on here about degenerative changes and got the answer back that SI is not a joint that is prone to degenerative changes unless you have either had trauma, or the joint has been stressed by pregnancy. I've never been pregnant and no trauma to that area.

I pointed out to GP that the report was fairly minimalist, didn't indicate if the sclerosis was unilateral or bilateral, didn't note if the joint space was enlarged or narrowed,etc. He agreed to ask for it to be reviewed, with particular reference to whether it showed sacroiliitis or not, and noting that I had never been pregnant.

I have just got the results of that review - done by the same person who initially reported it. I guess I was a bit naive thinking they would send it to a different radiologist. I've googled her and it seems her interest is primarily in clinical and interventional radiology in mostly Ob/gyn areas.

The report has come back with a single sentence as an addendum.
"Addendum: The finding is not typical for sacroiliitis, in case of persistent clinical problems x-ray of lumbar spine would be recommended".

Now what do I do? Is it really likely that it is just degenerative changes? Clinical problems are persistent, so is it worth having an x-ray of lumbar spine as suggested (when I currently have much more severe problems with thoracic and cervical areas anyway)?

Can someone point me to any information about degenerative changes in SI joints? or alternatively to something that says this is an unlikely cause.

Just for reference summary of my history is: lower back and butt pain since prob age 16, intermittent at first, becoming more persistent. Now aged 55, major disability for last 5 years. Limitations of spinal movement and less than 1 inch chest expansion. Morning stiffness relieved somewhat by exercise worse with rest. Respond to NSAIDs and NSD. Strong family history of lower back problems, pain in the butt, neck problems. Also strong fam. and personal history of "pinched nerves", carpal tunnel, non-specific gut stuff, etc. One male cousin diagnosed AS, everyone else with this kind of back stuff just degeneration. Strong family history of other autoimmune incl. RA. Other things in my sig. line.