When the child is somewhere between 2 and 6 years old, their cartilage patella starts forming a center of bone. Often, the kneecap will start to form bone at multiple centers within the cartilage. About 5 percent of the time, some of these bone centers do not fuse together with the main bone center. When this happens, it is called a bipartite patella, meaning a two-part kneecap. Whereas, these are often not painful; occasionally, kids can develop pain at this nonfused site on the patella. It can be preceded by an injury to the knee, but often it is only due to growth of the child.
‘Bro, You Ain’t Got No Kneecaps’–This TikTok Dad Has Fun Finding Out Kids’ Knees are Different
I was this week old when I learned my child was born without kneecaps. I learned this because of a video making the rounds on TikTok showing a dad’s hilarious reaction to making the same discovery about his young son.
The dad’s name is Dylan, and he shares a TikTok account with his wife Shelby at the handle @shelbanddyl.
Their video instantly went viral, collecting 5.7 million likes in five days and more than 36K comments.
“My husband just now finding out our son doesn’t have kneecaps,” a text overlay reads. Dylan has his eyes wide open, clearly in shock.
“Shelby!” he booms before turning to his son. “Bro, you ain’t got no kneecaps!”
The child starts crying, and Dylan says, “Don’t whine just ‘cause you ain’t got no kneecaps.”
Then, things get punny.
“He ain’t got a kneecap to stand on,” Dylan says as the couple laughs.
And, later: “Whenever I coach his Little League team, does that mean it’d be disrespectful if I asked the children to take a knee?”
“It’s uncapped? It’s just an open knee?” Dylan says, trying to figure out what children have instead of kneecaps.
“He will officially have a kneecap at 10 years old,” Shelby says from behind a camera.
In a caption, Shelby writes, “It only took him nearly 30 years to find this out.”
Don’t feel bad, Dylan. One commenter literally one-upped you.
“I was today years old learning kids have no kneecaps—I am 31,” says one person.
“You’re telling me my kneecaps are younger than me,” writes another.
It might not always feel that way—another comment can relate.
“If my kneecaps are 10 years younger than me, why do they feel like they’re 10 years older?” asked someone else.
But, since TikTok isn’t necessarily the gold-standard source of accurate health information, we spoke with pediatricians to find out if this kneecap story is nonsense.
Are Children Actually Born Without Kneecaps?
It turns out this fun TikTok rumor is, in fact, true. That said, there’s not “nothing” there.
“Babies are actually born with a structure called cartilage that resembles a kneecap,” says Tia Medley, MD, a pediatrician with MedStar Health. “The cartilage in that area, the same flexible material that gives our ears and noses shape, will become the bony kneecap, also known as the patella.”
Dr. Medley adds that the lack of a kneecap is actually to the child’s benefit, saying the cartilage allows for more flexibility during birth as well as while children are crawling and learning to walk.
So when do kids actually start to develop kneecaps? Daniel Ganjian, MD, FAAP, a board-certified pediatrician at Providence Saint John’s Health Center, says it starts in toddlerhood.
“[From] ages 2 to 6, the cartilage kneecap starts to harden into bone through a process called ossification,” Dr. Ganjian says. “By age 10 to 12, the kneecap is usually fully developed into a strong bone.”
When To Expect Kneecap Development
Both Dr. Medley and Dr. Ganjian agree that young children not having kneecaps does work to their advantage. However, kneecaps are essential as a child hits adolescence and beyond.
“The kneecap (patella) plays a key role in the knee joint by protecting the joint,” Dr. Ganjian says. “It acts like a shield for the joint by distributing the force from the leg muscles. [It also helps] to extend the leg. The muscles in the thigh pull on the kneecap, which helps to straighten the leg at the knee joint.”
How’s this for a fun fact?
“A healthy kneecap can support up to seven times a person’s body weight,” says Van Michelle Ruda, MD, a UTHealth Houston pediatrician affiliated with Children’s Memorial Hermann Hospital.
Sometimes, kneecaps don’t develop as they should, which warrants a discussion with a child’s pediatrician. In some cases, that pediatrician may refer a family to a specialist for further evaluation and support.
“Parents should seek medical attention if they notice their child has pain, swelling, a painful popping or clicking sound to the knee, or any abnormal appearance to the kneecap,” Dr. Ruda says.
One example of an abnormal appearance would be if the child has unequal leg lengths.
‘The Human Body Is Cool’
Dylan’s amazement at learning about kneecap development may be relatable for you and perhaps a naturally curious child. We live in our bodies, and it’s easy to not ask many questions (until something looks or feels off). But it sure is fun to learn something new about it.
“The human body is cool,” Dr. Medley confirms.
She also talks about how cool it is to not only have our own discoveries as parents (seemingly daily) but to watch our kids discover for themselves.
“Children have a unique perspective that can help parents and adults learn as well,” she says. “So many of the body’s functions depend on other body parts, and it can be limitless learning for kids. In addition, the human body is always growing and changing. Plus, once you throw in some of the involuntary sounds the body can make, kids really get a kick out of it.”
As far as resources to learn more fun facts about the human body, Dr. Medley recommends kidshealth.org to parents often, “as they have some great free resources for parents and children and present material in an understandable way. [Others include] National Geographic Kids [and] sites such as kidskonnect.com, scholastic, and knowyourself.com.”
Dr. Ganjian added two more: “The American Museum of Natural History’s Ology website has a section specifically devoted to the human body with games, quizzes, and creative activities,” he says. “Body by Tinybop is an interactive app that lets kids explore the human body in a fun and engaging way. They can zoom in on different organs and systems, learn how they work, and even play games.”
Bones Develop in Distinctive Ways Depending on Gender
The development and maturation of most human bones is very predictable. For example, orthopedic surgeons and others engaged in osteology (the study of bones) know that there are six different growth centers in the elbow, each initiating ossification (turning from baby cartilage into mature bone) at different ages depending on the child’s gender. During maturation, most bones go through a transition from cartilage to bone while at the same time grow in size.
Some of the bones in our bodies appear to not always follow a predictable development, and some do not always develop in every person. One particular class of bone that is notorious for this behavior is the sesamoid bones. The term sesamoid means sesame-like, and relates to their general appearance, often small and semi-round. When found, they are always present within the substance of a tendon where the tendon crosses over a joint.
The sesamoid bone is intended to hold the tendon slightly away from the joint in order to shift the mechanics and thereby improve the action of that tendon on the joint. A few of these sesamoid bones develop predictably, the most common and ubiquitous is the patella or kneecap. Another common set of sesamoid bones are found under the big toe.
Due to the unique positioning of these bones and the high stress they experience, they are at risk for developing problems often related to growing. When a child grows, it is actually their bones (thigh and leg bones, for example) that are increasing in length. The muscles and other surrounding structures have to be stretched out to accommodate this length change, and it often results in muscle tightness. This muscle tightness then increases the strain on the sesamoid bones.
When the child is somewhere between 2 and 6 years old, their cartilage patella starts forming a center of bone. Often, the kneecap will start to form bone at multiple centers within the cartilage. About 5 percent of the time, some of these bone centers do not fuse together with the main bone center. When this happens, it is called a bipartite patella, meaning a two-part kneecap. Whereas, these are often not painful; occasionally, kids can develop pain at this nonfused site on the patella. It can be preceded by an injury to the knee, but often it is only due to growth of the child.
The sesamoid bones of the big toe are also at risk for the development of bipartite bones and can often experience pain. When this happens in the foot (regardless of the presence of a bipartite sesamoid), it is called sesamoiditis or inflammation of the sesamoid.
No matter which sesamoid is inflamed, foot or knee, the treatment tends to be the same, at least initially. Modification of activity is the first treatment and often involves immobilization of the joint. Casting is uncommonly performed, but could be necessary. In children, if X-ray demonstrates the presence of a bipartite sesamoid, and the above mentioned treatment fails to resolve symptoms, then an MRI should be obtained to confirm the diagnosis.
If confirmed in the foot, then treatment could require surgery; but there is always the option of special shoe inserts. In the kneecap, surgery is much more likely to be required since there is no special shoe insert available. Surgery can take many forms depending on the size of the bipartite patella and needs to be individualized to the child.
There are many sources of pain around the knee and foot, but if your child starts to experience pain with motion of the big toe, or directly on the kneecap, then they may have sesamoiditis. Rest should be initiated. If your child’s pain is not improving after two weeks of rest, then you should contact, or see your doctor. You should also contact your doctor if the pain is associated with a fever or swelling that does not improve after 24 hours, as this might be a sign of a more significant injury.
Dr. Eric W. Edmonds is a pediatric and adolescent orthopedic sports medicine specialist at Rady Children’s Hospital-San Diego and an assistant professor of orthopedics at UC San Diego. He can be reached at [email protected].
