Among lower income groups, more than a third of women had never heard of osteoporosis.
More than eight out of ten did not know that the main cause was lack of a female sex hormone - and less than half that hormone replacement therapy (HRT) could stave it off.
A survey found that 51% of women suggested that ovarian, cervical and endometrial cancers all presented more of a threat to their health than brittle bone disease.
However, one in three women develop the condition, and many suffer hip or other fractures as a result.
Osteoporosis often strikes after the menopause, when women are producing less of the hormone oestrogen, which helps them maintain bone density.
Those who undergo premature menopause, or whose periods have stopped temporarily, perhaps as a result of an eating disorder, are thought to be particularly at risk.
Women are encouraged to undergo bone density checks after the menopause to make sure the condition is not emerging.
Taking replacement oestrogen can halt or slow the loss of bone density, and a healthy diet rich in calcium can also help ward off the disease.
Sex cure
Many women had different ideas about how to prevent the onset of osteoporosis.
Nearly one in three of those surveyed said that having regular sex could help stop brittle bone disease, while 18% correctly suggested a glass of wine a day might help.
Among lower income groups, more than a third of women had never heard of osteoporosis.
Dr Annie Evans, a woman's health expert, said: "Women aren't being given the information and education they need to make an informed choice."
Former newsreader Angela Rippon discovered four years ago that she had the early signs of osteoporosis.
She said: "I've beeing taking HRT for four years and continue to take it to prevent osteoporosis.
"I've witnessed how dreadfully debillitating the disease can be for otherwise healthy, active women.
"HRT can be a great life improver for many like me but doesn't necessarily work for everyone."