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The FRAX Score Calculator estimates the 10-year probability of major osteoporotic fracture (hip, spine, forearm, and proximal humerus) and hip fracture based on validated clinical risk factors. Developed by the WHO Collaborating Centre for Metabolic Bone Diseases at the University of Sheffield, FRAX is the world's most widely used fracture risk assessment tool, integrated into clinical guidelines by the National Osteoporosis Foundation (NOF), Endocrine Society, and International Osteoporosis Foundation (IOF).
Osteoporosis affects an estimated 200 million people worldwide and causes over 8.9 million fractures annually. In the United States alone, osteoporosis is responsible for approximately 2 million fractures per year, with direct costs exceeding $19 billion. Hip fractures are the most devastating, with 20-30% mortality within one year and only 40% regaining pre-fracture functional independence.
FRAX integrates clinical risk factors with or without bone mineral density (BMD) at the femoral neck to calculate personalized fracture probabilities. The algorithm was derived from prospective population-based cohorts from multiple countries, encompassing over 60,000 men and women with approximately 250,000 person-years of follow-up. It has been validated extensively and is calibrated for specific countries and ethnicities.
The clinical risk factors incorporated in FRAX include: age (40-90 years, strongest single predictor), sex (women have ~2x risk), BMI (low BMI increases risk), prior fragility fracture (1.8x risk), parental hip fracture (1.5x risk), current smoking (1.25x risk), glucocorticoid use (1.6x risk for prednisolone >=5mg for >=3 months), rheumatoid arthritis (1.3x risk), excessive alcohol (>=3 units/day, 1.35x risk), and optionally femoral neck T-score.
Treatment guidelines based on FRAX recommend pharmacological intervention when the 10-year probability of major osteoporotic fracture is >=20% or hip fracture risk is >=3%. Treatment options include bisphosphonates (alendronate, risedronate, zoledronic acid), denosumab, teriparatide, abaloparatide, and romosozumab. This risk-based approach helps target treatment to those most likely to benefit, avoiding unnecessary medication in low-risk individuals.
This calculator implements a simplified FRAX-like model using relative risk multiplication:
Risk = Base Rate x Age Factor x Sex Factor x BMI Factor x Risk Factor Multipliers
Base rates: Major fracture 3.5% (female) / 2.5% (male); Hip fracture 0.8% / 0.5%. Age factor increases 5% per year above 40. Each risk factor applies its relative risk multiplier. If femoral neck T-score is provided, it adds a bone density factor (T-score < -2.5 doubles the risk). Results are capped at 80% (major) and 50% (hip).
Note: This is an approximation. For official FRAX scores, use the validated model at sheffield.ac.uk/FRAX which uses country-specific mortality and fracture data.
The 10-Year Major Osteoporotic Fracture Risk includes hip, clinical spine, forearm, and proximal humerus fractures. The Hip Fracture Risk specifically estimates hip fracture probability (the most morbid outcome). Treatment thresholds: Major fracture risk >=20% or Hip fracture risk >=3% suggests pharmacological treatment is cost-effective. If Treatment Recommended = 1, discuss bisphosphonates or other anti-resorptive/anabolic agents with the patient. Always consider fall prevention, calcium/vitamin D supplementation, weight-bearing exercise, and lifestyle modifications regardless of FRAX score.
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Major fracture risk ~24% exceeds the 20% threshold. Treatment is recommended. Prior fracture nearly doubles the risk. Consider bisphosphonate therapy.
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Results
Major fracture risk ~1.5% and hip fracture risk ~0.2% — both well below treatment thresholds. Reassess in 5 years or if risk factors change.
FRAX (Fracture Risk Assessment Tool) is a computer-based algorithm developed by the WHO that calculates the 10-year probability of major osteoporotic fracture and hip fracture. It integrates clinical risk factors with or without bone mineral density to provide personalized fracture risk estimates for treatment decisions.
FRAX is recommended for postmenopausal women and men over 50 who have at least one clinical risk factor for osteoporosis but do not already have a clear indication for treatment (such as T-score below -2.5 or prior hip/vertebral fragility fracture). It is most useful for patients with intermediate risk (T-score -1.0 to -2.5, osteopenia).
In the US, the NOF recommends treatment when: 10-year hip fracture probability >=3%, or 10-year major osteoporotic fracture probability >=20%. These thresholds are based on cost-effectiveness analyses. Other countries may use different thresholds based on local healthcare economics.
No. FRAX can be used without DXA (using BMI instead), but incorporating femoral neck T-score improves accuracy. DXA is still recommended for postmenopausal women >=65 and men >=70, or younger if risk factors are present. FRAX helps decide who needs treatment among those with osteopenia (T-score -1.0 to -2.5).
FRAX does not account for: fall history, dose-response for some risk factors (e.g., number of prior fractures, glucocorticoid dose), recent fractures (higher risk in first 2 years), lumbar spine BMD (only uses femoral neck), vitamin D status, or certain secondary causes of osteoporosis. It may underestimate risk in some patients.
A prior fragility fracture approximately doubles the risk of future fracture. FRAX treats this as a binary variable, but the actual risk depends on number, recency, and location of fractures. A recent vertebral fracture carries higher imminent fracture risk than a remote wrist fracture. FRAX may underestimate risk in patients with multiple fractures.
Yes, in both directions. Low BMI (<20 kg/m2) increases fracture risk by about 50%, partly through lower bone density and less soft tissue padding. Paradoxically, very high BMI does not protect the spine and may increase ankle fracture risk. FRAX uses BMI as a continuous variable in its calculation.
Bisphosphonates (alendronate, risedronate, zoledronic acid) reduce vertebral fractures by 40-70% and hip fractures by 40-50%. Denosumab reduces all fractures by 20-70%. Anabolic agents (teriparatide, abaloparatide, romosozumab) are used for severe osteoporosis and provide even greater vertebral fracture reduction.
FRAX is validated for ages 40-90 only. It should not be used for premenopausal women or men under 50. For younger patients with secondary osteoporosis, other assessment tools and clinical judgment should guide management.
FRAX should be recalculated every 2-5 years, or sooner if risk factors change significantly (new fracture, starting glucocorticoids, significant weight change, DXA change). For patients near the treatment threshold, more frequent reassessment (every 1-2 years) is appropriate.
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