Welcome to the forum. Lots of inflammation here. I'm sure other people will be interested in your combination of PMR and Crohn's.

Sounds like we have the same lower back problems and pain. My rheumatologist doesn't see any evidence of ankylosing spondylosis (AS) but plenty of evidence of generalized inflammatory arthritis along with PMR. There is an entire family of spondyloarthritis types. Ankylosing spondylitis (AS) is only one type.
https://spondylitis.org/spondylitis-plus/an-updated-overview-of-spondyloarthritis-a-family-of-related-diseases/
Good luck with keeping your prednisone dose lower and eventually getting off prednisone again. It took 40 mg of prednisone initially and 13 years for me to get off prednisone after PMR was diagnosed. That was in addition to 15 years of intermittent high dose prednisone bursts to control flares of reactive arthritis and uveitis before PMR was diagnosed. PMR made a bad situation even worse and can coexist with spondyloarthritis.

A neurosurgeon says my entire lumbar spine is a mess and wants to remove much of it and fuse it all surgically.