I had SI joint issues. Honestly, what helped me the most was Katy Bowman, who is a biomechanist with online programs and books. PTs and doctors didn’t do sh!t.
If you check out her stuff, here’s what helped me:
-learning to untuck pelvis and drop ribs
-less sitting/sitting correctly (so you’re not sitting on your sacrum)
- learning to squat properly, with an untucked pelvis and vertical shins
-all of her other glute/pelvis strengthening exercises, like pelvic list, squats/lunges done the way she recommends, single leg strengthening exercises (single leg forward bend, single leg squat, arabesque)
The key is doing them properly so you’re strengthening your pelvis and flutes, not your legs.