When my youngest was still a newborn, I used to sit up with her in the middle of the night while my partner slept. My mind would wonder, and I would end up on my phone learning all manner of weird and wonderful (and useless) factoids.
One evening, I looked at my little girl bunched up in my lap, and noticed the dimples in her knees. Do babies have kneecaps? I thought to myself. The worm hole was open and I was sucked into it.
The answer is actually very straightforward: yes, babies do have kneecaps.
They wouldn’t show up on an X-RAY though.
Want to know why? Read on.
Cartilage Instead of Bone
When a baby is born, their kneecaps are there but they haven’t hardened into bones yet. Instead, they are made of cartilage.
This is the same stuff your nose and ears are made of, and parts of your airway. It’s hard but flexible, like a hose pipe.
This is why a baby’s kneecap wouldn’t show up under an X-RAY. They just aren’t dense enough to see on an X-RAY, but that doesn’t mean they don’t exist.
It’s a common myth that babies are born without kneecaps, so much so that many people state it as fact, but they are mistaken.
It’s not the finished article, that much is true, and the cartilage may even be in several pieces before it all fuses together at a later stage, but it’s there and it is doing a job.
As your baby grows, the cartilage will slowly begin to ossify – which is the technical term for turning into bone – but it takes a very long time to complete the process and become the patella we have as adults.
Why are Babies Born This Way?
It’s a good job the patella hasn’t formed in the womb, because it would make giving birth more difficult.
Babies are soft and supple precisely so they can pass through the birth canal. If their bones were strong and dense it would be much more difficult (and dangerous) to give birth. Imagine all those stiff limbs getting stuck, or even being broken. Ouch.
It also helps as your baby transitions from being a static slug like creature (don’t be offended, I include my own kids in this description), to being able to crawl, then toddle, then walk.
The softer kneecap makes their lives more comfortable since they spend some much of it on their knees in the early years. It also helps them when learning to crawl and walk because their legs are more flexible. The extra mobility in their legs helps them learn to balance.
Plus, think about all of the falling over kids do. Those knees take a lot of impact in the early years, so if their knee caps were rock hard we would have a nation full of kids with broken knee bones.
When Does it Change?
The soft cartilage will harden over time to form the bony patella we have for the rest of our lives, but it’s a long process.
It typically starts between the ages of 2 and 6. This is when the patella first begins to form, but can take up to 12 years to fully ossify. It would be unusual for a child to have a fully formed patella before 10, but between 10 and 12 years old the knee cap will have hardened.
During this time, all the bits of cartilage come together and form the patella, with a soft fat pad behind for support, as well as being supported by a couple of tendons. A very small amount of the cartilage will remain, but the majority will now be bone.
The long duration enables the child’s legs to develop and grow at the same time as the kneecap so the leg can work effectively with everything in proportion and in the right place.
It also means the knee cap gets stronger as the child gets stronger, and is able to cope with the demands an adult might put on it, such as playing sport, running, or working in a physical job.
