Fracture Risk Calculator
Estimate 10-year fracture risk using FRAX algorithm from age, BMD, and clinical risk factors. Enter values for instant results with step-by-step formulas.
Formula
10-year fracture probability based on age, sex, BMI, clinical risk factors, and BMD T-score
Risk is calculated using age-dependent baseline fracture rates modified by validated hazard ratios for each clinical risk factor. BMD T-score provides additional skeletal risk information. Treatment thresholds: Major fracture >= 20% or Hip fracture >= 3%.
Worked Examples
Example 1: Postmenopausal Woman with Risk Factors
Problem: A 70-year-old woman with BMI 22, previous wrist fracture, mother who had hip fracture, and femoral neck T-score of -2.8. No smoking, no glucocorticoids, no alcohol excess.
Solution: Age: 70, Female, BMI: 22\nRisk factors: Previous fracture (RR 2.0), Parent hip fracture (RR 1.7)\nBMD T-score: -2.8 (Osteoporosis)\nBase hip risk adjusted for age: ~2.5%\nWith multipliers: 2.5 x 2.0 x 1.7 x BMD factor = ~14.5%\nMajor osteoporotic: ~28%
Result: 10-year hip fracture risk: ~14.5% | Major osteoporotic: ~28% | High Risk - Pharmacological treatment recommended
Example 2: Male with Glucocorticoid Use
Problem: A 60-year-old man with BMI 28, taking prednisolone 7.5mg daily for rheumatoid arthritis, no prior fracture, no family history, non-smoker, T-score -1.8.
Solution: Age: 60, Male, BMI: 28\nRisk factors: Glucocorticoids (RR 1.6), Rheumatoid arthritis (RR 1.5)\nBMD T-score: -1.8 (Osteopenia)\nBase hip risk adjusted for age: ~0.8%\nWith multipliers: 0.8 x 1.6 x 1.5 x BMD factor = ~3.2%\nMajor osteoporotic: ~12%
Result: 10-year hip fracture risk: ~3.2% | Major osteoporotic: ~12% | Moderate-High Risk - Treatment should be considered
Frequently Asked Questions
What is the FRAX fracture risk assessment tool?
FRAX is a fracture risk assessment tool developed by the World Health Organization (WHO) Collaborating Centre at the University of Sheffield to evaluate the 10-year probability of bone fracture in patients. It integrates clinical risk factors with or without bone mineral density (BMD) measurements to estimate the likelihood of hip fracture and major osteoporotic fracture. The algorithm was developed from population-based cohorts from Europe, North America, Asia, and Australia involving nearly 60,000 patients. FRAX is available in country-specific models for over 70 countries, accounting for the different fracture rates and mortality patterns observed across populations worldwide.
What risk factors does the FRAX algorithm include in its calculation?
The FRAX algorithm incorporates several well-validated clinical risk factors that independently contribute to fracture probability beyond bone density alone. These include age (40-90 years), sex, body mass index (BMI), prior fragility fracture, parental history of hip fracture, current smoking status, glucocorticoid use (prednisolone 5mg daily or equivalent for 3 or more months), rheumatoid arthritis, other causes of secondary osteoporosis, and alcohol intake of 3 or more units per day. An optional femoral neck BMD T-score can be entered to improve risk prediction accuracy. Each factor contributes independently to the risk calculation through validated hazard ratios.
What is the treatment threshold for fracture risk scores?
Treatment thresholds for fracture risk vary by country and clinical guideline but commonly used benchmarks include initiating pharmacological treatment when the 10-year major osteoporotic fracture risk exceeds 20% or the 10-year hip fracture risk exceeds 3%. The National Osteoporosis Foundation (NOF) in the United States recommends these thresholds based on cost-effectiveness analyses for the US healthcare system. Some countries use age-dependent intervention thresholds where the treatment threshold increases with age to match the average population fracture risk. The UK NOGG (National Osteoporosis Guideline Group) uses an age-dependent assessment threshold approach rather than fixed intervention thresholds.
How accurate is the FRAX tool at predicting individual fracture risk?
FRAX has been validated in multiple independent cohorts and demonstrates good calibration at the population level, meaning predicted and observed fracture rates are generally well-matched across risk categories. However, individual-level prediction is inherently uncertain because fracture is a stochastic event influenced by factors not captured in the model, such as fall frequency, fall mechanics, and bone microarchitecture quality. Studies have shown that FRAX tends to underestimate fracture risk in patients with multiple vertebral fractures, high-dose glucocorticoid use, or recent fractures within the past 2 years. For this reason, clinical judgment should supplement FRAX scores, particularly in patients with additional risk factors not included in the algorithm.
What is the difference between hip fracture risk and major osteoporotic fracture risk?
The FRAX algorithm provides two separate 10-year fracture probability outputs that serve different clinical purposes. The hip fracture risk represents the probability of sustaining a hip fracture specifically, which is the most devastating osteoporotic fracture with significant mortality (approximately 20% within one year) and morbidity. The major osteoporotic fracture risk encompasses the combined probability of fractures at the hip, spine (clinical vertebral fractures), forearm (distal radius), and proximal humerus, which together account for the majority of fracture-related healthcare burden. Treatment decisions are typically guided by both outputs, with most guidelines using the major fracture threshold of 20% or hip threshold of 3%.
How does age affect fracture risk calculations?
Age is one of the strongest independent risk factors for osteoporotic fracture, with risk increasing exponentially after age 50 in both men and women. For women, the 10-year hip fracture risk approximately doubles with each decade of age beyond 50, independent of bone density changes. This is because age affects fracture risk through multiple mechanisms including declining bone quality and microarchitecture, increased fall propensity due to sarcopenia and balance impairment, and reduced protective reflexes. The FRAX algorithm captures the independent effect of age on fracture risk beyond what is reflected in BMD measurements. However, FRAX is only validated for ages 40 to 90, and risk estimates outside this range should be interpreted with caution.