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Small knee bone linked to arthritis

Tuesday 30th April 2019
The fabella, a small bone in the knee that is not present in many people, appears to be linked to arthritis; and it is becoming more common.
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There are plenty of possible causes for osteoarthritis, from age to injury to obesity. However, there is one other factor that seems to be linked to it; a small bone located behind the knee called the fabella. It was thought that this was an evolutionary throwback like the tailbone, and that it was dying out in humans. However, it appears to be coming back.

A new study from Imperial College London has found the fabella - which means ‘tiny bean’ in Latin, and was named as such based on its size and shape - has become more common over the last century. 

To discover this, the team looked at data from more than 21,000 knee studies spanning 150 years. In total, they reviewed 21,676 individual knees from 27 different countries. They found that in 1918, 11.2 per cent of the population had this bone in their body. By 2018, its prevalence had increased to 39 per cent.

The fact the number of fabellas is 3.5 time higher than it was a century ago is not just interesting because the bone was thought to be dying out in humans. It also has a significant impact on medicine, as it is linked to osteoarthritis.

The fabella has no use in humans. Some species of monkeys have the bone, and it can function in the same way as a kneecap for them, so it is thought we have evolved out of having a use for it. However, it can still cause knee pain, and sometimes get in the way of knee replacement surgeries.

It could also potentially cause arthritis. People who have osteoarthritis of the knee are twice as likely to have a fabella as people without the condition, which shows a clear link. However, more research needs to be undertaken to find out why this might be the case.

Written by Matthew Horton

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