Skeletal Variations: How Often Are Extra Bones Found?

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Adult human skeletons typically consist of 206 bones, but this isn’t invariably true.(Image credit: Devrimb via Getty Images)ShareShare by:

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It’s common knowledge that infants have a greater quantity of bones than grown-ups: While newborns can possess 275 to 300, with smaller bones merging and solidifying to form larger bones as they mature, most adults only have 206. (Having more diminutive, more pliable bones offers newborns additional suppleness, which allows them to curl up within the uterus and pass through the birth canal.)

But is it conceivable for adults to possess additional bones?

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Nonetheless, indications that an individual has a higher-than-usual quantity of bones are frequently subtle.

“It’s not difficult to be unaware of someone possessing an accessory bone,” Dr. Vandan Patel, an orthopedic physician at the Institute for Foot and Ankle Reconstruction at Mercy Medical Center in Baltimore, clarified to Live Science. Most of the time, accessory bones elicit no manifestations. “In many instances, we discover that an individual has an accessory bone when they undergo an X-ray for an unrelated ailment, and it’s identified incidentally,” he elucidated.

Even when accessory bones are observed in X-rays, they are commonly disregarded or misinterpreted as fracture remnants or alterations linked to aging, stated Eren Ogut, an associate professor of anatomy at Istanbul Medeniyet University. Altogether, “studies propose that they manifest in approximately 10 to 30% of the general population,” but “their actual prevalence is probably greater than generally acknowledged,” Ogut informed Live Science.

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Accessory bones are frequent in the foot and ankle, Patel stated. The os trigonum is the most prevalent accessory bone, he noted. “This is observed in up to 10 to 25% of individuals,” Patel remarked. “It’s positioned at the rear of the ankle joint. It may induce pain, particularly when pointing the toes and ankle downward, such as in a ballet dancer in an en pointe position.”

The os tibiale externum, additionally referred to as accessory navicular, is another typical accessory bone. “It is observed in up to 12% of the population,” Patel stated. “It’s situated on the inner aspect of the foot, adjacent to the typical navicular bone. Sometimes the navicular bone seems enlarged. It may provoke pain in the arch and is frequently associated with flat-foot deformity.”

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Doctors are also informed of several infrequent accessory bones, frequently through studies of corpses or medical imaging, Ogut conveyed. The os acetabuli, an accessory bone of the hip that might be linked to hip discomfort, is one such instance, he pointed out. This accessory bone is evident in fewer than 5% of the overall population, Ogut indicated in a 2025 review article in the Bratislava Medical Journal.

Occasionally, it’s possible to possess additional ribs. Up to 1% of individuals are born with one or even two supplementary bones in their neck, known as cervical ribs, according to the Cleveland Clinic. This uncommon bone lacks the appearance of a standard rib; it can be more vertical or diagonal rather than horizontal, like the ribs in the chest. Cervical ribs generally don’t cause issues, but they can result in pain or weakness in the arm. In such circumstances, physical therapy or medication can prove beneficial. A surgeon can also excise them, as they are non-essential, the clinic indicated.

Human skeleton quiz: What’s your understanding of the bones within your body?TOPICSLife’s Little Mysteries

Charles Q. ChoiSocial Links NavigationLive Science ContributorCharles Q. Choi serves as a contributing writer for Live Science and Space.com. His focus is on human origins, astronomy, physics, animals, and general science topics. Charles earned a Master of Arts degree from the University of Missouri-Columbia, School of Journalism, and a Bachelor of Arts degree from the University of South Florida. Charles has journeyed to every continent on Earth, sipping fermented yak butter tea in Lhasa, snorkeling alongside sea lions in the Galapagos, and even ascending an iceberg in Antarctica.Show More Comments

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