SI dysfunction in elderly

My 65 year old mother is suffering from back pain following a fall which caused a shift in her SI joint (one forward and one back) in addition to a broke tailbone. Her PT at the Mayo Clinic has prescribed some breathing exercises, yoga (cat/cow, child’s pose, pigeon, etc), light exercises (bridging, sidestepping, etc) to strengthen the muscles around the joint and the pelvic floor. She’s in quite a bit of pain for over a year now. What are your thoughts on including a light squat and deadlift program directed more at increasing her strength? What potential issues would we face given the SI joint dysfunctiontion?

You said she’s been in pain for over a year - did the fall precede this pain? Or has she been in pain and the fall was more recent? That wasn’t clear from the post, though I’m thinking it’s the former.

How / why did she fall?

How, specifically, was this SI joint injury diagnosed?

I agree that she should train. “SI joint dysfunction” is not a thing, so it’s not particularly relevant to training.

https://thelogicofrehab.com/2018/07/31/stop-telling-people-their-rotated-hips-are-causing-their-pain-seriously-stop-it/

There were actually three falls. In the first she fell in the entrance of the house and broke her tail bone. The next two falls occurred while walking on ice during the winter. The SI shift was diagnosed by multiple X-rays. I’ll take a look at the link, many thanks.

What programming adjustments do you recommend for someone of her demographic and situation? Would twice a week be adequate? Preferred?

Twice a week is a reasonable place to start, with the expectation that it would increase in the future. I do not think this situation needs a particularly unique programming approach, to be honest.