I feel your pain, literally. My right hip was replaced 6-months ago, and all is good on that side. Now my SI joint on the left side is complaining loudly. I had 6 weeks of PT for lower back pain, and was satisfied with the result, except that I couldn't walk upright, particularly up even a slight uphill grade. I'm hopeful that it's my right hip with transferred pain to my back. Headed back to the surgeon next week for evaluation. 74 YO male who likes to stay active.