Placeholder Image

Subtitles section Play video

  • Rob: Hello and welcome to 6 Minute English. I'm Rob.

  • Neil: and I'm Neil. Hello. (cracking knuckles)

  • Rob: Don't do that please, Neil, It makes my flesh creep.

  • Neil: Oh dear, if something makes your flesh creep it means you feel frightened or disgusted by something.

  • I don't know why I do it. It just feels nice.

  • Rob: But you'll end up with arthritis when you're older, you know.

  • Arthritis is a disease that causes pain and swelling in joints of the body.

  • Neil: That's an old wives' tale, Rob!

  • And that means an old idea or belief that has no scientific support.

  • Rob: OK, if you say so, Professor.

  • And since you're in a scientific mood, how about answering today's quiz question.

  • Which type of joint can you crack? Is it ... a) fibrous?

  • b) cartilaginous? Or c) synovial?

  • Neil: OK, this professor isn't feeling too clever today.

  • I'm going to have to take a guess and say, c) synovial.

  • Rob: OK. Well, we'll find out how smart you really are later on in the programme.

  • Now let's listen to Greg Kawchuk, Professor of Rehabilitation Medicine at the University of Alberta.

  • Rehabilitation means the process of helping somebody get better from an illness or injury.

  • Greg Kawchuk: We've recently been able to use some new technology through MRI imaging

  • to see for the first time what is actually happening inside the joint when someone pops or cracks their knuckles.

  • And because of that we're hopeful that we'll be able to start to ask questions about

  • why is it that some people can do this and other people can't.

  • Neil: What does MRI stand for?

  • Rob: It means Magnetic Resonance Imaging.

  • Hospitals use this technology to produce an image of the inside of a person's body.

  • Neil: So some people can't crack their knuckles. Can you, Rob?

  • Rob: I don't know, and I'm not about to try.

  • But it isn't just finger knuckles that crack you can do it with your neck, back, knees, ankles and toes.

  • Neil: Professor Greg Kawchuk says that comparing people who crack their knuckles and people who don't

  • might provide some insight or understanding into whose joints are healthier.

  • Rob: Sounds interesting.

  • But what actually happens when you crack your knuckles, Neil?

  • Neil: Well, when you stretch or bend your finger to pop the knuckle,

  • you're making the bones of the joint pull apart... like this...(cracking knuckles)

  • Rob: Please don't do it again!

  • Neil: Well, it stretches the space around the joint

  • and surrounding fluid and causes a decrease in pressure.

  • As a result, gas dissolved in the fluid becomes less soluble

  • or less able to be dissolved leading to the formation of bubbles.

  • Now when you stretch the joint far enough, these bubbles burst, producing the "pop" sound.

  • Rob: Ouch! Excellent well, thanks for the biology demonstration there, Neil ...

  • Neil: Any time! Any time, Rob!

  • Now let's hear from the professor again about the medical value of research into knuckle cracking.

  • Greg Kawchuk: When our engineering colleagues do this between

  • two flat surfaces say of ceramic or porcelain...

  • When they do this and they pull them apart quickly

  • and there's a little bit of fluid in between

  • they can use electron microscopy to see there's been tremendous damage to the surfaces of the joints.

  • But for some reason we don't see that in the human joint.

  • There's something that makes it very resilient.

  • Rob: Interesting stuff!

  • So scientists have performed experiments to imitate what happens in a human joint

  • when you crack your knuckles.

  • And when you quickly pull apart a pair of ceramic or clay,

  • tiles with fluid between them, it causes a lot of damage to the surface of the tiles.

  • Neil: So why don't human joints get damaged as well?

  • Rob: Well, the scientists don't actually know.

  • They can see the damage to the tiles using electron microscopy

  • that's a very powerful microscope.

  • But it's not clear what makes the human joint so resilient to damage

  • and resilient in this context means returning to its original shape

  • after being stretched or bent.

  • Neil: Right. But with further research scientists may be able to find out and then use this

  • information to help people with joint problems.

  • Rob: Or they could create synthetic or man-made materials

  • which can withstand wear and tear better than current ones.

  • Withstand means not be damaged by something

  • and wear and tear means damage as a result of ordinary use.

  • Neil: Can we have the answer to today's quiz question now, Rob?

  • Rob: Yes, of course. So which type of joint can you crack? Is it ... a) fibrous?

  • b) cartilaginous? Or c) synovial?

  • Neil: And I said: c) synovial.

  • Rob: You are quite clever actually because you are right, or was it a good guess?

  • Neil: It was a good guess.

  • Rob: Well done! And synovial is the name for the fluid that surrounds this type of joint.

  • Neil: OK. So can we hear the words we learned today again?

  • Rob: Of course. We heard:

  • make your flesh creep

  • arthritis

  • an old wives' tale

  • rehabilitation

  • MRI (which means "Magnetic Resonance Imaging")

  • insight

  • soluble

  • ceramic

  • resilient

  • synthetic

  • withstand

  • wear and tear

  • Neil: Well, that's the end of today's 6 Minute English.

  • We thought it was a cracking show!

  • Please join us again soon.

  • Both: Bye.

  • Rob: Go on Neil, one more time.

  • Neil: Here we go. (cracking knuckles) Feels great!

  • Rob: Horrible!

Rob: Hello and welcome to 6 Minute English. I'm Rob.

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it