It really depends on the problem to understand the cure (or fix).
I have a bad sacro-iliac and it can get very bad if I do a lot of bending or moving heavy objects around. It lasts for days or weeks depending on the level of stres I exert on this joint. Medially, they know little about sacro-iliac issues.
They do make a special belt that holds your hip bones together. I have found that by wearing this belt, the pain subsides much quicker. I can ride with the belt and it doesn't get any worse. I have since switched to a recumbent trike, and the ride couldn't get much more comfortable as long as the path is reasonable.
If the problem is purely related to the spine, this won't do anything for you. Doctors were looking at my spine as the cause of the pain. It would be 2-1/2 years before the doc's started looking elsewhere and found the sacro-iliac to be the real problem just before I was about to be commited to a wheelchair. Many of the symptoms are similar to lower back pain, but in the end, this very 'fixed' joint can cause serious pain if it has to much mobility.