A 74-year-old woman is brought to the ED after a fall. X-ra…

 A 74-yeаr-оld wоmаn is brоught to the ED аfter a fall. X-ray confirms a right femoral neck fracture. She has a 12-year history of rheumatoid arthritis managed with long-term prednisone (10 mg/day) and recently started alendronate. Which factor in this patient's history MOST significantly compounds her risk for fragility fracture beyond age and female sex alone?