Had a knee replaced? Read this wacky but true warning about flossing

Some 4.5 million Americans are living with knee replacements right now -- and if you're one of them, there's a new infection risk you need to be aware of.

This wacky but true warning doesn't have anything to do with the surgery itself. It doesn't matter if you had your knees replaced last week, last month, last year or years ago.

And you're not going to believe how it starts: With flossing!

Yes, one of the best oral hygiene habits around can in some cases cause an unusual type of infection in patients with artificial knees.

A woman in Wisconsin who had been aggressively flossing as part of her dentist's orders found herself in the ER with knee pain and chills. Docs found fluid in her knee -- and when they tested it, found that she was suffering from infection with Streptococcus gordonii.

This isn't the same bacteria that causes strep throat, but it's part of the same family -- and it's usually found in the mouth, not the knee.

As it turns out, her aggressive flossing caused her gums to bleed, allowing the bacteria to enter the body. Most of the body can fight off Streptococcus gordonii, but an artificial joint has no immune component -- giving the bacteria a place to gather and grow.

It's hard to say how common this specific type of infection is, but about 1 in 100 patients who've had knee replacements end up suffering from infections in those knees unrelated to the surgery -- infections that in some cases can strike up to 20 years later.

And when they do hit, they can be quite serious.

Of course, I won't say don't floss. Flossing is essential to good oral hygiene -- but if your gums bleed when you floss, you're opening the door to some pretty nasty bacteria.

Once they get inside, your knees might be the least of your worries.

Those same bacteria have been linked to heart attack and stroke, which is why folks with good oral hygiene tend to have better cardiovascular health than those with bad teeth and bleeding gums.

So keep brushing (with fluoride-free toothpaste) and floss daily. But if your gums bleed when you floss, don't ignore it.

It's usually a sign of gum problems such as gingivitis. Visit a dentist or periodontist who can clean your gums before it becomes a much bigger problem in another part of the body.