Hello and Welcome to Science She Wrote the show where I talk about science
unsurprisingly given the title. I'll be discussing everything from vaginas to
vampires to other things that don't being with 'v', medical history we'll be looking
at weird things your body does and you don't quite know why, all the good stuff
to do with human biology and the body so if you've got any suggestions of videos
you'd like to see or questions you like me to answer please remember to
leave a comment in the box below and I will try my very best to answer them for
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And visit my blog at ScienceSheWrote.com where I post more interesting science
stuff. We're hopefully going to be moving house in the next couple of weeks so I
hope to keep putting out videos and posts while that's happening but please
bear with me
there's a bit of a delay but hopefully once we've moved I'll have a much better setup
for filming so I'll be able to get videos out a lot quicker and a lot easier so
good stuff to come!!
Today's video is the first in a series of 'Things I used to believe as a child
which aren't actually true' and I need to think of a better title because that is
way too long so if you have any suggestions please let me know below.
It's basically going to be about all those things you used to believe as a kid
things your parents used to tell you or things you used to hear on the playground
which just have no basis in reality so things like watching TV will give you
square eyes or eating the crusts on your sandwich will give you curly hair
or the reason that Pringles are so addictive is because they put hormones
in them and I'm going to be discussing all of these and basically tell you what
a bunch of **** the are but using science to explain why.
And the first thing we're going to be discussing is the myth that cracking
your knuckles will give you arthritis.
So when you crack your knuckles you're actually manipulating the joint that's
found between your metacarpals and your proximal phalanges.
One of my favorite biology words phalanges. It just feels so nice in the mouth (weirdo!!)
So the metacarpals are the bones that form the palm of your hand and your proximal
phalanges are the bones that form the first part of your finger so the bit
between the knuckle and the first bend in your finger there. Your metacarpophalangeal
joint is a type of synovial joint. The end of the metacarpal bone and
the end of the proximal phalangeal bone which come into contact at the
joint a covered by articular cartilage and this reduces friction as the joint
moves. Movement of the joint is also a lubricated by synovial fluid which is
enclosed in a joint capsule.
It was originally thought that the popping noise you hear when you crack
your knuckles is a result of a bubble popping within this synovial fluid.
So as the two articulating bones are pulled apart the pressure within the
joint capsule actually reduces and this allows gases which are dissolved in the synovial
fluid to come out of solution and form a bubble or cavity. The subsequent collapse
of this bubble is what was thought to actually result in the audible sound.
Now recent research has shown that the sound actually comes before the bubble's collapse.
Researchers performed a real-time MRI scan of somebody popping their metacarpophalangeal joint.
The flash seen on the MRI scan indicates the formation of the
bubble or cavity
and the popping noise was actually heard the same time as the flash.
So it's actually the result of a bubble forming that results in an audible sound
not the bubble popping!
But this weird habit predispose to joint problems or arthritis? Well medical
research has failed to demonstrate any link between knuckle popping and the
development of arthritis or other joint problems. Studies as early as 1975
have failed to demonstrate a link. A study in 1990 which examined 74 habitual knuckle
crackers against 226 non-knuckle crackers found no link between the knuckle
cracking and arthritis.
Although the knuckle cracking group were more likely to suffer from hand swelling
and reduced grip strength
the study was unable to confirm that knuckle cracking resulted in these
functional impairments.
Another study in 2011 looked at the hand radiographs of 215 people and compared
the knuckles of the non-knuckle crackers with the knuckle-crackers.
The study concluded that habitual nut cracking....
The study concluded that habitual knuckle cracking no matter how frequent
or a number of years did not result in increased risk of arthritis and if
you're still not convinced by all that medical data
look no further than Californian medical doctor Donald Unger who cracked the
knuckles on his left hand at least twice a day for over 50 years
that's a total of over 36,500 knuckle cracks but
never deliberately cracking the knuckles on his right hand. At the end of
this long one-man study
no arthritis or other ailments were found in either hand. And for his
contributions to scientific research
Donald won an Ig-Nobel prize for medicine in 2009 and no that's not the
same as a Nobel Prize!
So the conclusion seem to be that you can keep cracking your knuckles as much
as you like it might annoy or gross out the people around you but it's unlikely
to give you arthritis!
(Terrible American accent) 'There's something wrong with the left phalange!'