The evolutionary-discarded bone making a strange comeback

The fabella is a small bone that grows in the knee muscle tendon. As far as we know, it serves no purpose, and used to be extremely rare. Yet in the last century, the number of reported cases has grown by 3.5 fold.

There’s no doubting the numbers – 11% of cases in 1918 compared to 39% in 2018. The number of people that have a fabella bone has gone up significantly, and researchers have yet to figure out why. The strange phenomenon was first noticed by Dr Michael Berthaume, who analysed 21,676 knees across 27 different countries with his team from Imperial College London.

For now, all we have are hypotheses, with some scientists attributing this increase to improvements in our diet. Since sesamoid bones generally form in areas with good muscle tension, and as humans have evolved to be taller and heavier over the years, the fabella could be developing in order to reduce friction caused in the knee. It’s an interesting hypothesis, but it doesn’t answer all the questions.

For there seems to also be a link between the fabella and arthritis. People who suffer from joint pain are actually twice as likely to have this small bone in their knees. How these two phenomena are connected remains unclear, but we do know that this bone can cause pain and discomfort. Doctor Berthaume even goes so far as saying that the fabella could soon be the “appendix of the skeleton”.