Women complaining of knee pain are less likely than men to be recommended for total knee replacement surgery, a study in Tuesday's issue of the Canadian Medical Association Journal suggests.

Toronto researchers conducted the study with two standardized or "mystery" patients, one male and one female, both with moderate knee osteoarthritis, reporting the same symptoms and similar lifestyles.

Each patient visited 67 doctors in Ontario who consented to include their data in the study. Thirty-eight were family physicians, while 29 were orthopedic surgeons.

The results showed that the physicians visited were twice as likely to recommend total knee replacement surgery, known as arthroplasty, to the male patient as to the female patient.

Lead author Dr. Cornelia Borkhoff of Toronto said the research suggests a gender bias in the treatment of patients who need orthopedic surgery.

The female patient, Dorothy Aungier, 72, said she didn't expect so many doctors would treat her differently for the same problem.

"It was amazing. Some doctors said 'here's some pills' and gave me a prescription," she told CBC News. "One doctor said just walk on grass."

Sixty-seven per cent of the doctors recommended surgery for the man, while only 33 per cent recommended it for Aungier.

"I don't understand that, I really don't," she said. "That got me, because they're knees. Does it matter any different if they're male or female?"

Researchers are also struggling to understand the results. The numbers are small, but the study showed both general practitioners and orthopedic surgeons had the same bias.

Because few of the participating physicians were female, just 12, the researchers said they could not examine the effect the sex of the doctor had on their findings.

Toronto physician Gillian Hawker, one of the study's authors, speculated the doctors may decide against surgery if a woman doesn't appear sold on the idea.

"It may be that women are more doubtful about the benefits and they may present themselves as not quite convinced, compared with men, and that might turn off the doctor to thinking, okay, let's go ahead with surgery," she said.

Whatever the reason, Hawker said people should demand better care.

"We need to teach these women to be better advocates for themselves, to better express their pain and disability, to not take no for an answer," she said.

Stereotypes, patient presentation styles play a role

The study said there are three possible explanations for the findings. First, decisions to recommend arthroplasty may have been based on conscious attitudes or 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," it said.

A second possible explanation is that the participating physicians' treatment recommendations were a result of an unconscious bias based on gender. Unconscious bias occurs when a patient automatically activates a stereotype in the physician's memory.

The study said such a bias can result from years of experience telling doctors that women don't receive the same benefit from total knee arthroplasty as men.

A third explanation is that despite identical clinical scenarios, the presentation style of the male and female standardized patients may have differed because of their gender, the study said.

Male patients more 'business-like'

"Women typically present their symptoms using a narrative style, speaking more openly and personally about their complaints, whereas men typically present their symptoms using a business-like style, describing their complaints in a more factual or reserved manner," it said.

Dr. Michael Dunbar, an orthopedic surgeon in Halifax, said that what the researchers found is startling, but he questions the significance of a such a small study.

"They've only included one male and one female, so it's not very robust," he said. "You know, I personally don't think as a group of surgeons that we are going around biasing based on gender. You know, I really don't think that is happening."

Aungier had both knees replaced after the research was done and said they're feeling "great.

"It's definitely worth doing. It's definitely worth doing the surgery," she said.

Aungier said she used to crawl up and down stairs like a crab and that she fears she would still be doing that if she hadn't shopped around for the right treatment.