Scientists discover a useless knee called the Fabella is making a comeback

Every schoolboy knows that the human skeleton has 206 bones.

However, it may be necessary to rewrite textbooks – after scientists thought that evolution had been lost to the benefit of evolution, made a curious comeback.

The fabella, a tiny bone that sits inside the tendon behind the knee, is more than three times more prevalent than it was 100 years ago – and now, two in five people have one.

With a diameter of less than half an inch, the bone – found in our primate ancestors – has been dubbed the "skeletal appendage" because it is apparently useless.

Today, scientists believe that modern diets, which have made us bigger and heavier, have put our knees to the test, which has led us to grow the extra bone to relieve the pressure .

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But there is a problem. Having a fifth bone in the knee could bring on cartilage, a lesion that can cause osteoarthritis.

In fact, people suffering from this painful condition – which affects a 45 year old in England – are twice as likely to have a fabella.

Some experts now say that fabella should be systematically removed if found.

Researchers from Imperial College London have examined more than 21,000 scientific studies carried out over a period of 150 years, in which fabella bone was identified during scans and dissections.

They discovered that 11.2% of the world's population had a fabella in 1918. But, last year, this figure had more than tripled to 39%, according to the review published in the Journal of Anatomy.

Dr. Michael Berthaume, head of the study, said, "This research is very interesting because it is extremely rare to modify the human skeleton, which affects everyone in the world.

"We have no idea and we can only guess what he is doing. It could therefore prove to be the appendix of the human skeleton.

"We hope that, through his study, we can help people with osteoarthritis pain and determine if people with fabellas should have them removed."

The fabella, which means "little bean" in Latin, does not seem to have any reason to be evolutionary and would have disappeared with our primate ancestors before its reappearance in the medical reports in 1875.

People are taller and heavier than in the past, so it is important for the gastrocnemius muscle to be larger behind the knee, creating stress and friction.

Fabella, which is found in the tendon tying the muscle to the femur, can eliminate some of this stress by providing a smooth surface to the sliding of the tendon. This is certainly the benefit that it has in dogs, cats and some monkeys, all of which have a bone surplus.

But experts believe that fabella can create uneven force on the knee, increasing cartilage damage. It could also be painful after a knee replacement surgery because the extra bone stays in place while sinking into the femur. When this part of the bone is replaced and there is no more depression to hold it, the tendon "slams" from left to right with each stride, causing pain.

Dr. Berthaume said, "As we evolve into great apes and humans, we seem to have lost the need for fabella. It seems that it only causes us problems, but the interesting question is why it is making such a comeback. "

The study, published in the Journal of Anatomy, explains in detail how they examined 21,676 individual knees from 27 countries and dating back to 1875.

The data come from a variety of sources, including X-rays, MRI scans, and anatomical dissection.

Fabella is known as a sesamoid bone, which means that it develops in the tendon of a muscle.

A patella is the largest sesamoid bone in the human body.

The study showed that there was a link between osteoarthritis and the presence of a mysterious bone.

People with osteoarthritis of the knee are twice as likely to present a fabella as non-osteoarthritis sufferers.

But, say the researchers, we can not yet say that the presence of the bone causes the disease.

It is also believed that harmful bones affect knee replacement surgeries and can cause discomfort itself.

Its use in modern man is widely debated, but considered negligible or nonexistent.

However, we think that in our evolution, it had a more important role to play before becoming irrelevant.

It may have acted as a kneecap for these animals before evolution made it redundant in our ancient human ancestors.

It is thought that its resurgence over the past 150 years is the result of improved nutrition following the wars between men who assaulted the twentieth century.

Better nutrition means that humans are now bigger, stronger and heavier than ever in our history, putting more pressure on our horses.

The knees are therefore subjected to much stronger pressure and the bone grows during exercise of the tendon, which may have led to the resurgence.

Dr. Berthaume explained, "The average human being today is better fed, which means we are bigger and heavier.

"It was done with longer tibias and bigger calf muscles – changes that both put increasing pressure on the knee.

"This could explain why fabellae are more common now than they once were."