Tidbit #7 - April 2, 2011

It's great, isn't it? Your fingers are feeling rather uncomfortable, until... pop! In that little noise is the answer to your pain. It hurts for a split second, and then it's gone, along with your discomfort. So how does this process work? How do we crack our knuckles?

Question: What happens when we crack our knuckles?


Answer: There are a few possible answers to this question:

1. I knew a possible solution to this question before I began researching. I had heard all about what it was. I had heard that it was air pockets formed in between your knuckles, which you pop, causing that beautiful noise.
2. An article on Kidzworld.com states that "when you crack your knuckles, you're essentially pushing the joint into or out of its normal position. A lubricant called synovial fluid (SF) is found between the knuckles, and when you crack them, you pull the bones apart, reducing the SF pressure, which quickly form bubbles which expand and burst, causing the pop! (Re: Yahoo! Answers question)
3. Another explanation from How Stuff Works explains that this bubble in your knuckle forms during a process called "cavitation". It takes roughly half an hour after you've cracked your knuckle for the gas to go into the SF, creating a bubble for you to pop! (Re: Yahoo! Answers question)

So, we have three answers. All of them point to the same thing:

Our knuckles "crack" when air bubbles in between them burst from pressure.