@susan63, My PMR is currently in remission but I've had flares twice and started on 20 mg of prednisone. I haven't had any experience with spine stress fractures but hopefully other members with PMR can share their experience with you. I do have degenerative disk disease along with an undiagnosed suspected condition of camptocormia which makes it difficult to walk standing straight up. I did find some information that sounds like it could be related to your symptoms.

"Can polymyalgia rheumatica affect the spine?
Introduction. Polymyalgia rheumatica (PMR) is a common inflammatory disease in older people characterized by shoulder and/or pelvic girdle, and cervical and, occasionally, lumbar pain. Interspinous bursitis has been suggested as a potential cause of spinal symptoms." --- Interspinous bursitis is common in polymyalgia rheumatica, but is not associated with spinal pain: https://arthritis-research.biomedcentral.com/articles/10.1186/s13075-014-0492-2

Can you provide an update after your back X-rays, MRI and bone density scan?