February 25, 2024
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The Fabella: The Extra Bone in Your Knee

Our bodies are remarkable creations, full of intricate details and hidden surprises. While we often think of bones as a static framework, some individuals have a surprising addition to their knee joint—a small, sesamoid bone called the fabella. This tiny bone is a lesser-known aspect of human anatomy but carries intriguing insights into the diversity of our skeletal structures. Let’s explore the fabella and the role it plays in the human body.

What Is a Fabella?

The fabella is a small, sesame seed-sized bone that can be found within the knee joint. It typically develops within the tendon of the lateral head of the gastrocnemius muscle, which is one of the calf muscles. The term “fabella” comes from the Latin word for “little bean.”

Variation in Human Anatomy

One of the fascinating aspects of the fabella is its variability in human anatomy. Not everyone has a fabella; it’s estimated that only about 10-30% of people have this extra bone in their knee joint. This variation is a testament to the diversity of human bodies and the complexity of our skeletal structures.

Function and Controversy

The function of the fabella has been a subject of scientific debate for many years. It’s believed to be a sesamoid bone, which means it forms within a tendon. Sesamoid bones, like the fabella, are thought to reduce friction, increase the mechanical advantage of muscles, and protect tendons from excessive wear and tear.

However, the exact function of the fabella in the human body remains a topic of ongoing research. Some people with fabellae experience no issues, while others may develop conditions related to these small bones, such as fabella syndrome, which can cause pain and discomfort.

Clinical Significance

For individuals with fabellae, these tiny bones can become a point of interest in the context of medical imaging and diagnosis. Radiologists and physicians may take note of the presence or absence of a fabella during knee examinations or surgeries, as it can have implications for joint health and treatment approaches.

Evolutionary Traces

The presence of the fabella in some humans is thought to be a vestige of our evolutionary history. It’s believed to be a remnant of a larger sesamoid bone that was more significant in our primate ancestors, particularly in those that had a more quadrupedal (four-legged) gait.


The human body is a treasure trove of complexity, and the presence of the fabella in some individuals exemplifies the diversity and variations within our species. While the exact function of the fabella remains a subject of study and debate, it serves as a reminder that our bodies carry traces of our evolutionary past and continue to surprise us with their unique features. So, if you ever discover that you have a fabella in your knee, know that you’re part of an intriguing aspect of human anatomy that makes each of us wonderfully unique.

Picture Courtesy: Google/images are subject to copyright


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