I was looking at getting a magnetic rug for mine with SI issues, thread yesterday about them in TR, several people have suggested back on track, I plan on speaking to my physio to see what she thinks would be best.
Love Back on Track. I've used the mesh sheet for four years now - great on its own before riding or competing or in winter under a stable rug to help keep those muscles relaxed, without over-rugging. I also use the leg wraps for a horse prone to LGL in very cold weather. Their products work for me when my back is bad so I'm pretty sure they help the horses too.