FRAX Explained: What the Fracture Risk Score Means, and the Four Things It Cannot See

What does FRAX actually calculate?

FRAX estimates your probability of breaking a bone in the next ten years. It returns two numbers: the risk of a major osteoporotic fracture, meaning spine, hip, forearm or upper arm, and separately the risk of a hip fracture.

Its purpose is to move the conversation past a single density number. Two women can have identical bone density and quite different fracture risk, because age, weight and previous fractures each add risk of their own. A T-score alone cannot express that, which is why a scan result is a starting point rather than an answer. See bone density testing for what the scan itself measures.

It is free, hosted by the University of Sheffield, and has country-specific versions because fracture rates differ between populations. Run the version for the country you live in: using the wrong one produces a number that does not mean what you think it does.

What does it ask, and why does each item matter?

• Age and sex. Risk rises steeply with age independently of density, which is why an older woman with better bone can still carry higher risk.
• Weight and height. Low body weight raises risk, partly through less cushioning and partly through lower bone mass.
• Previous fracture as an adult. Among the strongest single predictors. A break from a fall at standing height counts, and many women do not think of a wrist broken at 55 as relevant.
• Parent with a hip fracture. The risk runs in families, independently of your own density.
• Current smoking and alcohol of three or more units a day.
• Glucocorticoids, current or past prolonged oral steroid use.
• Rheumatoid arthritis and secondary osteoporosis causes, which include early menopause, coeliac disease, hyperthyroidism and long-term liver disease.
• Femoral neck bone density. Optional. FRAX works without it, and works better with it.

What do the numbers mean once you have them?

In the United States, the Bone Health and Osteoporosis Foundation has long framed treatment thresholds for postmenopausal women with low bone mass at a 10-year probability of 3% or more for hip fracture or 20% or more for major osteoporotic fracture. Other countries use different thresholds, some age-dependent rather than fixed.

These are decision aids for a conversation, not automatic instructions. A result above threshold opens a discussion about treatment; a result below it does not close the subject if something the tool cannot see is pushing your risk up.

That gap is the entire point of the tool. A density number alone would have treated these two women identically.

What are the four things FRAX cannot see?

1. It does not ask about falls. Falls history predicts fractures about as strongly as anything on the list, and FRAX does not capture it. A woman who falls repeatedly can have a reassuring score and a genuinely high risk, because most fractures happen when someone falls rather than spontaneously.
2. Risk factors are yes or no, not dose or duration. Two years of high-dose glucocorticoids and three months of low-dose count identically. Ten cigarettes a day and forty count the same.
3. It does not use spine density. Only femoral neck density is entered, so a woman whose spine is considerably worse than her hip can be underestimated.
4. It does not account for the reason for early menopause. Premature ovarian insufficiency and surgical menopause add years of low estrogen that the tool does not weigh directly, and those years matter. See menopause and bone loss.

There is a fifth, less discussed: a previously undiagnosed vertebral fracture changes the calculation completely, and many are painless. Height loss over the years is the usual clue.

How should you use it before an appointment?

Run it, write down both numbers, and bring the questions the numbers raise rather than the numbers alone. If your result sits near a threshold, the factors FRAX cannot see are the ones that should decide. Raise these explicitly:

• "Have I fallen in the last year?" Answer honestly, including near-misses and trips that did not result in injury.
• "What is my spine density, not just my hip?"
• "How old was I at menopause, and does that change this?"
• "Have I lost height?" A measured comparison beats a remembered one.
• "Should we look for a vertebral fracture I do not know about?"

What does FRAX not replace?

It is not a diagnosis and it does not replace bone density testing. It is a risk estimate designed to help decide whether treatment is worth starting, and it says nothing about which treatment. Our pages on osteoporosis treatment and medications compared cover that separate question.

A low score in a woman who falls frequently, or who has already fractured a vertebra without knowing it, is false reassurance rather than a clean bill of health. Used well, FRAX prompts better questions. Used as a verdict, it can talk a woman out of treatment she needs.

What can you do regardless of the score?

Everything that reduces fracture risk without a prescription applies whatever FRAX says: adequate calcium and vitamin D, resistance and weight-bearing exercise, balance work, stopping smoking, moderating alcohol, and removing the trip hazards in your own home.

Falls prevention deserves particular emphasis precisely because FRAX ignores it. Our guides to exercise for bone density, calcium and vitamin D and osteopenia cover the parts you control. If you are already on treatment and wondering about a pause, see stopping osteoporosis medication.

Why does the same score mean different things at different ages?

FRAX returns an absolute ten-year probability, not a comparison with your peers, and that catches people out in both directions.

A woman of 52 with a 12% major osteoporotic fracture risk has a number that looks modest but is high for her age, and it implies decades of accumulating risk ahead. A woman of 78 with the same 12% has a number that is unremarkable for her age. Absolute risk rises with age no matter what, which is why some countries use age-dependent thresholds rather than the fixed 3% and 20% used in the United States.

The practical consequence: if you are in your early fifties and your score sits below threshold, that is not a reason to stop paying attention. It is a reason to establish a baseline and protect the years when bone loss is fastest.

What should you do if you cannot get a density scan?

Run FRAX without one. It was designed to work that way, which is the point of including clinical risk factors rather than requiring imaging. The output is less precise but still usable, and in many health systems it is what decides whether a scan gets ordered at all.

If the no-density result lands anywhere near a threshold, that is the argument for requesting the scan rather than a reason to stop. Our pages on what a DEXA scan costs and DEXA versus at-home bone tests cover the practical routes, including why home tests are not equivalent.

How does FRAX fit with everything else?

It sits between the scan and the treatment decision. The scan measures density; FRAX converts density plus clinical factors into a probability; the probability opens or closes a treatment conversation; and the treatment conversation is a separate question about which drug.

What it never does is tell you whether you are falling, how strong you are, or whether your home is safe. Those determine a large share of real fracture risk and none of them appear in the calculation. A woman with a modest FRAX score, poor balance and a loose rug at the top of the stairs is in more danger than the number implies.

That is not a criticism of the tool so much as a description of its scope. Use it for what it estimates, and handle the rest separately.