BMD T-Score (Left Femoral Neck)

A hip fracture in your sixties or seventies can change everything. It often marks the end of independent living, and the one-year mortality after a hip fracture is sobering. The bone density of your femoral neck, the narrow part of your thigh bone just below the ball of your hip joint, is the single best predictor of whether that fracture is in your future.

This test gives you a number called a T-score, which compares your bone density to that of a healthy young adult at peak bone mass. Knowing this number in your forties or fifties, rather than waiting until your seventies, gives you decades to act.

What the T-Score Actually Measures

A BMD (bone mineral density) T-score at the left femoral neck is calculated by measuring the mineral content of the bone in that specific spot using a low-dose X-ray scan called DXA (dual-energy X-ray absorptiometry). The result is expressed in grams per square centimeter, then converted into a T-score by comparing it to the average peak bone density of healthy women aged 20 to 29.

A T-score of 0 means your bone density matches that of a healthy young adult. A T-score of -1 means your density is one standard deviation below that reference. A T-score of -2.5 means it is two and a half standard deviations below, which is the formal threshold for osteoporosis.

The femoral neck is one of the most clinically meaningful sites to measure. It directly reflects the strength of the bone where most hip fractures occur, and it is less likely to be artificially inflated by age-related changes in the spine such as arthritis or calcification of the surrounding tissues, which can make lumbar spine readings misleading in older adults.

Hip Fracture Risk

The femoral neck T-score is one of the strongest single predictors of hip fracture risk in any test you can order. In a foundational meta-analysis of bone density and fracture outcomes, each one standard deviation drop in hip BMD increased hip fracture risk roughly 2.6-fold. The relationship is continuous, meaning risk climbs steadily as the score falls, rather than jumping at a single threshold.

In a study of 42,198 adults, the femoral neck T-score significantly predicted hip, non-spine, and major osteoporotic fractures in both people with and without type 2 diabetes. For a given age and T-score, the 10-year fracture risk was comparable between these groups, meaning this number works as a risk gauge across populations.

What this means for you: a T-score below -2.5 puts you in the formal osteoporosis range, where fracture risk is high enough that most guidelines recommend treatment. But waiting for that threshold is the wrong strategy. A T-score between -1.0 and -2.5, called osteopenia, signals that bone loss is already underway and is the right time to intervene.

All-Cause and Cardiovascular Mortality

Lower femoral neck BMD is not just about fractures. A meta-analysis of prospective cohort studies found that lower bone mineral density was associated with higher all-cause and cardiovascular mortality. In a study of 15,076 adults, maintaining normal BMD was linked to lower risk of death from cancer and heart disease.

In one analysis of 817 adults, the femoral neck was the optimal site for predicting coronary artery disease risk by BMD, with a cut-off value around -1.70. The connection likely runs through shared mechanisms involving inflammation, vitamin D status, and the biology of vascular calcification, but the practical takeaway is the same: a low femoral neck T-score is a signal worth taking seriously beyond bone health alone.

Cognitive Decline

In a study of 3,651 older adults, low bone mineral density at the femoral neck was associated with an increased risk of developing dementia. The femoral neck appeared more informative for this association than lumbar spine BMD. The biology connecting bone and brain is still being mapped, but the consistency of the signal across cohorts suggests this is not a coincidence.

Reference Ranges

The standard T-score thresholds were established by the World Health Organization based on the bone density of non-Hispanic White women aged 20 to 29 in the NHANES III dataset. These cutpoints are applied across all ages, sexes, and ethnicities. Your specific lab may use slightly different reference data, so compare your results within the same lab over time for the most meaningful trend.

Note: An updated reference using NHANES 2005 to 2014 data found a peak femoral neck BMD of 0.888 grams per square centimeter in non-Hispanic White women, which would shift more people into the osteoporosis and low bone mass categories than the standard reference. The thresholds above remain the most widely used in clinical practice.

The T-score is a continuous measure, not a hard cliff. Someone with a T-score of -2.4 is not meaningfully different from someone at -2.6, even though only one is formally diagnosed with osteoporosis. Treat your number as a position on a sliding scale, not a pass-fail grade.

Why Site Matters: Femoral Neck vs. Lumbar Spine

DXA scans typically measure bone density at multiple sites, but they do not always agree. In a study of 3,740 older adults, using the lowest T-score from lumbar spine plus right and left femoral neck more than doubled osteoporosis prevalence compared with using a single site. The femoral neck was lower than the total hip in 86% of adults aged 50 and over.

In older adults, the lumbar spine reading is often inflated by arthritis, vertebral compression changes, and aortic calcification, which add density to the X-ray image without adding actual bone strength. The femoral neck is more reliable in this group. If your spine T-score looks normal but your femoral neck T-score is low, trust the femoral neck.

Tracking Your Trend

A single T-score is a snapshot. The real value comes from tracking how it changes. Bone loss is gradual, typically a fraction of a percent to a few percent per year, but the trajectory matters more than any one reading. A score that is stable at -1.8 over five years is a very different situation from a score that has dropped from -1.0 to -1.8 over the same period.

Get a baseline scan in your forties or fifties at the latest, earlier if you have risk factors like family history of osteoporosis, early menopause, long-term steroid use, or low body weight. Repeat the scan in 1 to 2 years if your baseline shows osteopenia or you are starting an intervention. If your baseline is normal and you have no major risk factors, every 2 to 3 years is reasonable.

Use the same DXA machine when possible. Different scanners can produce slightly different readings, and small differences in calibration can shift a T-score by enough to change the diagnosis. Within-lab comparisons over time are far more meaningful than absolute values from different machines.

What to Do If Your Result Is Abnormal

If your T-score is in the osteopenia range, the goal is to slow bone loss and address modifiable risk factors. Companion tests worth ordering alongside a low T-score include 25-hydroxy vitamin D, parathyroid hormone, calcium, phosphorus, alkaline phosphatase, and a basic kidney panel. These help identify treatable causes of bone loss like vitamin D deficiency, hyperparathyroidism, or kidney disease that is silently affecting your bone metabolism.

If your T-score is at or below -2.5, the conversation shifts toward treatment. An endocrinologist or a primary care physician comfortable with bone health can help you weigh medication options. The FRAX score, which combines your T-score with clinical risk factors, helps quantify your 10-year fracture risk and guides treatment decisions. A T-score below -2.5 alone, or a FRAX major osteoporotic fracture risk of 20% or more, typically warrants treatment.

Even with a normal T-score, fragility fractures still occur. Bone microarchitecture, muscle strength, and fall risk all contribute to whether you actually break a bone. A trabecular bone score, an additional measure derived from the same DXA scan, can refine your risk estimate when added to the T-score.