Lower back SI issues is common in MS and often related to muscle spasms between that area and the hip. If you look at medical image of the SI and hip you will see that the muscles attach from the back to the hip which is what keeps the hip joint and back stable. All in all your physio therapy/heat and proper exercises at home should assist with the dysfunction. It is what it is. Yoga is helpful and after that tai chi

Ms seems to weaken the hip muscles, PT and exercises that target those, should help with balance and proper gait. The flexor muscles that surround the ankle can also be targeted and strengthened by PT to help with foot drop... good luck!

I’m not a dr or nurse just has something similar happening fell though it was my tailbone. For years I was told it was my MS. I finally found a pain management dr that diagnosed me with SI JOINT DYSFUNCTION. In the years it took to get diagnosed I lost my ability to walk. I had foot drop it messed up my hips. I’m still trying to heal. Don’t give up

That sounds rough. Best wishes with the PT . Welcome to the team.