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The Debunker: Are Babies Born With Kneecaps?

by Ken Jennings

Babies: they're everywhere, especially when we fly coach. But how much do we really know about them? Ken Jennings of Jeopardy! fame asked if he could spend April debunking some persistent misconceptions about babies, in hopes that it will persuade the universe to deliver Beyoncé's twins this month. Hey—she cancelled Coachella on doctor's orders. It could happen.

The Debunker: Are Babies Born With Kneecaps?

This one was a favorite on those "Re: FW: Re: FW: FW: amazing trivia facts" emails that used to circle the Earth thirty times a day. Do those lists still exist? Did they ever colonize Facebook and find a new life? Anyway, alongside other dubious things on those lists (your heart stops when you sneeze! Winston Churchill was born in a ladies' room during a dance!) the nation's aunts and grandmothers very much wanted you to know one important fact about babies: they have no kneecaps.

kneezy does it

There's a grain of truth to this, which we'll get to in a second. But first of all: no! What kind of a boneless, McNugget-like baby are you imagining, if you think its skeleton is optional at birth? Humans are, in fact, born with more bones than they'll have as adults. That's because many baby bones are small segments (like the ones in their skulls) that'll fuse together into a single bone as they get older.

So when babies are born, all of their bones are actually a mix of bone tissue and cartilage. The patellae, or kneecaps, are no exception. They're almost invisible on baby x-rays, because they're made almost entirely of cartilage in utero, which may be how this myth originated. Some experiments have suggested that human bones never ossify, or harden, until they need to bear weight. (Kneecaps, for example, aren't fully ossified in boys until they're almost ready to start kindergarten.) This may be an evolutionary strategy, allowing the body to divert energy to more important early development (like the brain!) until hard bones are actually needed for important toddler activities like waddling around the house and putting the cat in the dryer.

Quick Quiz: Shane Stant served an 18-month prison sentence for his infamous January 6, 1994 attack on the kneecap of what famous person?

Ken Jennings is the author of eleven books, most recently his Junior Genius Guides, Because I Said So!, and Maphead. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at ken-jennings.com or on Twitter as @KenJennings.