Got a fabella?

The fabella is a small bone located in a tendon behind the knee (note the tiny bone at ther ear of the femur head).

This bone virtually disappeared over the course of human revolution, but it’s making a comeback. Looking at 21,000 studies of the knee spanning the past 150 years, researchers found that the fabella is three times more common than it was in 1918. In that year, just 11 percent of the world population had the bone. Last year, it was present in 39 percent of us.

It’s true that the average human body is taller and heavier than it was in 1918, resulting in longer shinbones and larger calf muscles—changes that put the knee under increasing pressure. But nobody knows what the fabella is supposed to do or why it’s making a comeback. In old world monkeys, it played a role in knee muscle mechanics. But in humans it’s anybody’s guess. As one scientist said, “perhaps the fabella will soon be known as the appendix of the skeleton.”

There’s definitely a down side to having this bone. It can cause knee pain. People with osteoarthritis in their knees are about twice as likely to have this bone than those who do not have arthritis. It can also create additional challenges for knee replacement surgery.

I’ve got some knee x-rays hanging around somewhere. I’m going to check them out.

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