Scientists are confused by the re-emergence of what they assumed was an averted extra leg behind the knee.
By the turn of the century, about one in 10 people was a fabella-bean-shaped bone, which, like knee joints, is hidden in tendons.
Scientists had assumed that the rate in the population had remained stable or decreased. But research has now revealed that almost four in 10 people – close to four times 100 years ago – now have the extra bone.
The researchers looked at over 21,000 registrations of knees that span 150 years from over 27 countries. 19659002] "We don't know what fabella's function is – no one has ever looked at it!" Said Dr. Michael Berthaume, lead author of the study at Imperial College London in a statement.
"The Fabella can behave like other sesamoid bones to reduce friction within tendons, redirect muscle forces or, as at the kneecap, increase the mechanical force of that muscle. Or it could not do anything at all."
The results were published in the Journal of Anatomy on April 17 and showed that in 1918, fabellae was present in 11.2 percent of the world's population. In 2018, they were present in 39 percent.
The Fabella is a sesamoid bone – the term is used for bone growing within the tendon. The kneecap is the largest sesamoid bone in the human body.
Berthaume said: "We are taught that the human skeleton contains 206 bones, but our study challenges this. The Fabella is a bone that has no apparent function and causes pain and discomfort to some and may require removal if it causes Problems.
"Perhaps the fabella will soon be known as the skeletal supplement," said Berthaume.
found a statistical correlation between the presence of the bone and arthritis, those with osteoarthritis of the knee were twice as likely to have the extra bone that may also get in the way of knee surgery. The interesting question is why does it make such a comeback, " said Berthaume.
A theory is nutrition. "We found signs of fabella resuscitation all over the world, and one of the few environmental changes that have hit most countries in the world is better nutrition."
– Imperial Medicine ( @IperperMed) April 17, 2019
Another theory is that the bone is not as useless as thought, but can provide some mechanical advantage as it does in ancient worlds where it acts as a kneecap.
Berthaume said: "Today, the average person is better nourished, which means we are louder and heavier. This came with longer shinbones and larger calf muscles – changes that both put the knee under increasing pressure. This could explain why fabellae are more common now than they once were. "
Bones have long been known to develop and strengthen in response to mechanical forces.
The researchers speculate that a fabella can form under the influence of certain mechanical forces. But they think there is likely to be a genetic element – not all people can have the ability to form one of the extra bones.