Tiny Knee Bone, Once Lost in Humans, Is Making a Comeback

The fabella (small dot on the right of each scan) is a little bone embedded in a tendon of the knee in some people.
MICHAEL BERTHAUME, IMPERIAL COLLEGE LONDON

Textbooks will tell you that the human body contains 206 bones. But sometimes, there are 208. The fabella, a small bone in a tendon behind the knee, was lost over the course of early human evolution, but these days it’s becoming more common, according to a study published this week (April 17) in the Journal of Anatomy.

The bone has been linked to knee problems, and the authors argue that the fabella should be taken into account when treating people with knee pain.

Michael Berthaume of Imperial College London and his colleagues gathered data from more than 21,000 studies of the knee spanning the past 150 years, and found that between 1918 and 2018, the fabella has become more than three times ...