Hi GabesMom. Sorry we had to meet here, but I do know a bit about the surgeries you went through, so hopefully I can help.
I used to work as a physical therapy assistant, and I've been in the operating room to observe some hip (and knee) replacement surgeries. I asked one of the orthos at the hospital if I could watch, because I wanted to know how it was being done, so I could treat and educate my patients better, and he kindly allowed me to. And it did help me with my job.
I was quite surprised. Joint replacement surgery, Especially the hip, is not a delicate operation, like most people think of surgery. It's more like a construction project. Lots of things get moved around, and quite a lot of force is used at times. Tendons and ligaments get stretched, muscles have to be moved out of the way, and pinched nerves are a common side effect.
The sacroiliac joints are partially the two halves of your pelvis held together by very strong bands of ligaments, so that they have very little movement, with the sacral vertebrae in the middle. In fact there's disagreement in the medical community about how much movement is "normal", and we're talking about 2 to 17 degrees. Women, while giving birth, release a hormone called relaxin, that allows those ligaments to loosen up more than normal so the baby can pass.
Add all of that together, with the multiple hip revisions you have had, and the diagnosis sounds very likely. It's a matter of the ligaments being moved and pulled on during the operations too many times. The ligaments usually recover, but it takes time. The pelvic ligaments are extremely strong, and it takes a lot of force to stretch them. But they usually return to their original shape and position in time.
Be patient, and the injections for those are to help you through the rough spots while the ligaments recover. I wish you luck, and keep pushing.
Short version; Osteoarthritis, scoliosis, lumbar spondylolisthesis, sciatica, hip dysplasia, bipolar disorder, migraines, macular degeneration, TIA's (they think), insomnia, and a rogue's gallery of other things...
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God, grant me the serenity to accept the things I cannot change, The courage to change the things I can, And the wisdom to know the difference.