Diagnosing osteoporosis means confirming a low bone mineral density (BMD) and recognising the fracture that may already have occurred. Because the disease is silent, the diagnosis rests on measurement — and on imaging of vertebral fractures that cause no symptoms — rather than on how the patient feels.
Physical examination
The physical examination of a patient suspected of having osteoporosis has two purposes: to find signs of a secondary cause, and to detect a vertebral fracture or a high risk of falling. The findings and what each suggests are:
| Finding | Suggests |
|---|---|
| Enlarged thyroid gland | Hyperthyroidism |
| Atrophic testicles | Hypogonadism |
| Blue sclera with yellow-brown teeth and hearing loss | Osteogenesis imperfecta |
| Loss of more than 4 cm from the tallest remembered height | Old vertebral fracture |
| Loss of more than 2 cm from the previous height measurement | New vertebral fracture |
| Body mass index below 20, or weight loss of more than 5% | High risk of fracture |
| Localised tenderness over a spinous process, kyphosis, reduced distance between the lower ribs and the pelvic brim | Vertebral fracture |
| Abnormal posture and gait, reduced muscle strength, postural hypotension, impaired consciousness | Higher risk of falling |
Who should be tested
Bone mineral density is measured by dual-energy X-ray absorptiometry (DXA), described in the next section, and the US Bone Health & Osteoporosis Foundation (BHOF) recommends testing in these groups:
| Population | Recommendation by BHOF |
|---|---|
| Women age ≥ 65 years and men age ≥ 70 years | Consider BMD testing |
| Postmenopausal women and men age 50-69 years | Consider BMD testing based on risk profile |
| Postmenopausal women and men age ≥ 50 years | Consider BMD testing with history of adult-age fracture |
| Adults with certain conditions or medications | Consider BMD testing for those with conditions (e.g., rheumatoid arthritis, organ transplant) or taking medications (e.g., glucocorticoids, aromatase inhibitors, androgen deprivation therapy) associated with low bone mass or bone loss |
Diagnostic criteria
The T-score is the number of standard deviations by which a patient’s bone mineral density differs from the mean of a young adult population, measured by dual-energy X-ray absorptiometry (DXA). The WHO defines osteoporosis from the T-score:
| Classification of WHO | T-score |
|---|---|
| Normal | -1.0 or greater |
| Low bone mass (osteopenia) | Between -1.0 and -2.5 |
| Osteoporosis | -2.5 and below |
| Severe osteoporosis | -2.5 and below + fragility fracture |
A DXA measurement should sample the lumbar spine (L1–L4), the femoral neck, the total hip, and the 33% radius.
A fragility fracture is a fracture that occurs with little force. In a patient with one, osteoporosis may be diagnosed even without measuring bone mineral density, provided the fracture is not explained by another cause such as multiple myeloma.
The BHOF treats the diagnosis as definite in a postmenopausal woman or a man older than 50 years who has either:
- a DXA T-score of ≤ -2.5, or
- a DXA T-score between -1.0 and -2.5 with a FRAX 10-year probability of major osteoporotic fracture above 20% or of hip fracture above 3%. FRAX is the tool that combines bone mineral density with clinical risk factors, described in Risk factors for osteoporotic fracture.
Vertebral fracture assessment
Most vertebral fractures are silent, so they are looked for with imaging. Vertebral fracture assessment (VFA) uses the same machine as DXA, with lateral imaging, to find vertebral fractures. The method is semi-quantitative: the height of each vertebral body is measured, and the reduction in body height gives the number and severity of fractures. VFA is indicated when the T-score is below -1.0 and at least one of the following is also present:
| Indication Criteria for use of VFA | Details |
|---|---|
| Required Baseline | T-score is < -1.0 |
| Plus one or more of the following: | |
| Age | Women ≥ 70 years of age or men ≥ 80 years of age |
| Height Loss | Historical height loss > 4 cm (1.5 inches) |
| Prior Fracture | Self-reported but undocumented prior vertebral fracture |
| Medication | Glucocorticoid therapy equivalent to ≥ 5 mg of prednisone or equivalent per day for ≥ 3 months |
Findings such as an enlarged thyroid gland or atrophic testicles, or a fracture that another cause such as myeloma could explain, raise the question of which other diseases, deficiencies or drugs may be behind the bone loss.