Table 1 Diagnostic criteria for osteoporosis
Normal bone density
-1 or greater
Between -1 and -2.5
-2.5 or less
Established (severe osteoporosis)
-2.5 or less plus a fragility fracture
(World Health Organization 1994)
*T-score is the measurement of bone mineral density by dual energy x-ray absorptiometry scan. A T score of
the hip and/or spine is considered to be the gold standard.
BMD is measured by dual energy x-ray absorptiometry (DEXA) scan (WHO 1994). The lower
the BMD score the greater the risk of fracture. Osteoporosis can result from factors that lead to bones not reaching high density in the first place, such as genetics, poor childhood diet, or because of events that cause bones to lose density quicker than usual, including medications, lack of oestrogen (early menopause), disease or a combination of factors (Poole and Compston 2006).
Rheumatoid arthritis, parental fracture and high alcohol intake increase fracture risk independently of BMD (Kanis et al 2008). Patients at risk of osteoporotic fracture are usually identified after a fragility fracture or opportunistically because of the presence of clinical risk factors (Box 1).