Introduction: Two million out of the UK’s 5 million routine diagnostic computed tomography (CT) scans performed each year incorporate the thoraco-lumbar spine or pelvic region. Up to one third reveal undiagnosed osteoporosis or vertebral fractures. We developed an intervention, ‘PHOENIX’, to facilitate early detection and management of osteoporosis in people attending hospitals for CT scans. Methods & analysis: A multi-centre, randomised, pragmatic feasibility study. From the general CT-attending population, women ≥65 and men ≥75 years attending for CT scans are invited to participate, via a novel consent form incorporating FRAX Fracture Risk Assessment questions. Those at increased 10-year risk (within the amber or red zones of the UK FRAX graphical outputs for further action) are block randomised (1:1:1) to 1) PHOENIX intervention, 2) Active Control or 3) Usual Care. The PHOENIX Intervention comprises i) retrieving the CT scans using the NHS Image Exchange Portal, ii) Mindways QCT Pro software analysis of CT Hip and Spine Bone Density with CT Vertebral Fracture Assessment, iii) sending the participants’ GP a clinical report including diagnosis, necessary investigations, and recommended treatment. Baseline CT scans from groups 2 and 3 are assessed with the PHOENIX intervention at study end. Assuming 25% attrition, the study is powered to find a predicted superior osteoporosis treatment rate with PHOENIX (20%) versus 16% among patients whose GPs were sent the FRAX questionnaire only (Active Control) and 5% in the Usual Care group. Five hospitals are participating, to determine feasibility. The co-primary feasibility outcome measures are a) ability to randomise 375 patients within 10 months and b) retention of 75% of survivors, completing their 1-year bone health outcome questionnaire. Secondary 1-year outcomes include osteoporosis/vertebral fracture identification rates and osteoporosis treatment rates. Stakeholder acceptability and economic aspects are evaluated. Ethics and dissemination REF19/EE/0176. Dissemination will be through the Royal Osteoporosis Society. Trial registration number ISRCTN14722819