Recognize this sound?
听过这个声音吧？
If you pop or crack your joints, you probably do.
如果你掰过手指，那你很可能听过
What happens to our joints when we crack them?
掰手指的时候指关节会怎么样呢
And is it bad for you?
这样做有害吗？
Synovial fluid is this lubricant-like substance that's found in between your joints.
滑液是手指关节内类似润滑剂一样的东西
It kind of looks like an egg yolk.
看着有点儿像蛋黄
So when you stretch out your joint,
所以，活动关节的时候
you are releasing gas, and that gas forms a bubble and it collapses and pops.
你实际上是往滑液里释放了气体，这些气体会形成一个一个的气泡，气泡爆破就会发出声音
In order to crack the same knuckle again,
要想再掰同一个关节
you have to wait about 20 minutes for the gas to return back to that fluid.
要等气体再次回到滑液里，这个过程差不多需要20分钟
So how is that different from a pop you hear when you stand up quickly?
那么，掰手指的声音和快速起身时听到的声音有何不同呢？
The sound you're probably hearing then
那个时候很可能听到的
is the snapping sound tendons make when slide between muscles or over bones.
是肌腱在肌肉之间或骨头上拉伸时发出的爆裂声
When a joint moves, the tendon snaps quickly over it and it makes a popping sound.
关节活动时，肌腱迅速拉伸，就会发出爆裂的声音
So is the knuckle cracking habit safe? Probably.
那活动关节的习惯安全吗？可能吧

Donald Unger was sort of a self-described researcher
唐纳德·昂格尔就自称
who chose to pop the joints in one of his hands for 60 years, but not the other one.
是一位掰手指掰了60年的研究员，但他只掰一个手的手指
And he wanted to find out if popping your knuckles would actually give you arthritis.
他想知道掰手指到底会不会得关节炎
After 60 years of doing it, he found that
60年过去了，他发现
he didn't have any more arthritis in one hand than in the other.
两只手都没有得关节炎
Most medical sources might agree with these findings.
尽管大多数医学资料可能与这些发现都一致
But there's still a chance it's not good for you.
然而，掰手指仍然有可能对大家不好
One 1990 study did find that cracking your knuckles over a long period of time
1990年的一项研究确实发现，长期掰关节
led to hand swelling and decreased scrip strength,
会导致手指粗大，并且会削弱手指的力量
but there hasn't been any follow-up research on that.
仅此而已，目前并没有更深入的研究
So while cracking your knuckles might not be bad for you,
所以，掰手指可能对你并没有什么害处
there's still no guarantee that your popping habit won't annoy the people around you.
但不保证你的这个习惯不会影响到你身边的其他人