Dentists often advise that flossing is essential for healthy teeth.

But a 65-year-old US woman took this advice a little too far and ended up in hospital, but not with an injury you might expect.

The woman, who had undergone a knee-replacement five years earlier, arrived at a local hospital in Wisconsin with a swollen and inflamed right knee.

When doctors took a sample of the fluid around the joint they discovered it was infected with a bacteria typically found in the mouth, Streptococcus gordonii.

While this seemed unexpected at first, the doctors then learned that the women had started a "vigorous dental flossing regimen prior to the onset of symptoms".

It appears that by flossing so vigorously that her gums bled, the S. gordonii travelled through her bloodstream to the knee prosthesis.

Prosthetics do not have an immune system, making them easy targets for bacteria to grow a biofilm around them. Infections around prosthetics are mostly commonly caused by the bacteria Staphylococcus aureus and Staphylococcus epidermidis.

In a case report published in the British Medical Journal Case Reports doctors said this was the first case of oral S. gordonii being linked to an infection of a prosthesis in the US.

To treat the bacterial infection, doctors opened up the women's knee and cleaned her replacement knee. She was also placed on long-term antibiotics.

Ala Dababneh, an infectious disease specialist involved with the case, told Live Science the event was extremely rare and people with prosthetics should continue flossing their teeth.

"I don't want people to worry that just flossing is going to cause them an infection in their prosthetic joint," Dababneh said, from the Mayo Clinic in Minnesota.