A TINY knee bone thought to be near extinction is making a comeback – and it may be causing osteoarthritis.
The fabella was only present in 11.2 per cent of people’s knees globally back in 1918 and scientists thought it served little or no purpose in our bodies.
But new research carried out at Imperial College London has found it can now be found in 39 per cent of adults around the world.
And people with osteoarthritis of the knee were twice as likely to have one as those without the condition.
The 3.5 fold increase has baffled scientists, who say further studies are needed to find out whether the mysterious fabella serves any physical purpose. Until now, it’s often been described as pointless.
Dr Michael Berthaume, from Imperial’s Department of Bioengineering, said: “We don’t know what the fabella’s function is – no one has ever looked into it!
“The fabella is a sesamoid bone, meaning it grows in the tendon of a muscle – the kneecap, for instance, is the largest sesamoid bone in the human body.
“The fabella may behave like other sesamoid bones to help reduce friction within tendons, redirecting muscle forces, or, as in the case of the kneecap, increasing the mechanical force of that muscle. Or it could be doing nothing at all.”
‘STRAIN ON OUR FRAMES’
In the study, published in the Journal of Anatomy, authors used X-rays, medical research and MRI scans to analyse 21,676 knees from 27 countries, including the UK, dating back to 1875.
The researchers admitted the link with osteoarthritis but say it cannot yet say whether it causes the condition, and if so, how.
It can cause pain and discomfort on its own, and can get in the way of knee replacement surgery.
Dr Berthaume said: “We are taught 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 might require removal if it causes problems.
“Perhaps the fabella will soon be known as the appendix of the skeleton.”
The bone may have had a more important role in history, acting as a kneecap in animals before evolution made it redundant in our ancient human ancestors.
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Its resurgence is thought to be a result of improved nutrition, which means humans are taller, stronger and heavier than ever before in history – and this all places a strain on our frames.
Dr Berthaume said: “The average human is better nourished, meaning we are taller and heavier.
“This came with longer shinbones and larger calf muscles – change which both put the knee under increasing pressure. This could explain why fabellae are more common now than they once were.”