Canadian doctors may be unconsciously discriminating against women when it comes to deciding who would benefit from knee replacement surgery, finds an intriguing study.

The study, in this week's issue of the Canadian Medical Association Journal, involved a bit of undercover work. Two "mystery" patients with moderate knee osteoarthritis -- one male and one female -- went to see 38 family doctors and 29 orthopedic surgeons in Ontario complaining of the same symptoms of knee pain.

They asked the doctors if they were good candidates for total knee replacement surgery (known as arthroplasty).

The researchers found that doctors were twice as likely to recommend knee replacement surgery to the male patient compared to the female patient:

• Sixty-seven per cent of physicians recommended arthroplasty to the male patient.
• Only 33 per cent of physicians recommended it to the female patient.

As well, the male patient was referred to an orthopedic surgeon 35 per cent more often than the female patient.

"The woman, with the same level of disability and pain (as the man), was much less likely to be told she needed surgery," said one of the study's co-authors, Dr. Gillian Hawker.

The study's lead author Dr. Cornelia Borkhoff suspects that unconscious prejudices among doctors may explain the differences, since "physicians are susceptible to the same social stereotyping that affects all of our behaviour," she notes.

But the differences may also be explained by overt discrimination based on sex.

"Some physicians have been shown to take women's symptoms less seriously and attribute their symptoms to emotional rather than physical causes and to refer women less often than men for specialty care even when women have a relatively greater degree of disability," her study notes.

Dr. Hans Kreder, an orthopedic surgeon and co-author of the study says it may also be because of the different ways women and men describe their injuries to the doctor.

"The woman might present her situation in more of a narrative," he said. "The man may be more as brief facts. And it's possible that because of that, the severity of the problem isn't transmitted in the same way."

Dr. James Wright, the study's principal author and a professor at the University of Toronto Faculty of Medicine's Department of Health Policy Management and Evaluation says acknowledging that gender bias may affect physicians' decision-making "is the first step toward ensuring that women receive complete and equal access to care."

"The next step is to develop creative interventions to address these disparities in health care."

With a report by CTV's Graham Richardson