Here's what really causes that gross popping noise you hear in your joints

As we start to get older, there are several things we may notice happening to our bodies: we don't have enough energy to handle those late Friday nights quite like we used to, our hair and skin starts to need a lot more upkeep than the occasional scrub or wash, and - for some more than others - our joints begin to make a terrible cracking noise every time we get up or stretch out.

Sometimes, the "pop" or "snap" of a joint will be accompanied by pain, and other times by somebody nearby asking, "WAS THAT YOUR FOOT?" but, quite often, it doesn't hurt at all. It's just a weird, annoying occurrence that most of us just seem to have accepted as part of the human life cycle. But what causes it?

Well, first of all, it should be noted that joint cracking isn't as simple as it's sometimes made out to be. There are a number of things that could cause it, and some are more serious than others - but we'll get to that in a bit.

One of the most common (and usually harmless) causes of a popping noise is the release of gases from the synovial fluid in your joints. The fluid, which contains oxygen, nitrogen, an CO2 (air, basically), is used to lubricate the joints, and a sudden movement can cause the gases to be rapidly released as bubbles - which then burst. If this is the cause of the noise, you won't be able to crack the joint again for a short amount of time, as the bubbles need a while to return to the synovial fluid.

Another, also perfectly normal, cause is the movement of tendons and ligaments - particularly in places like the knee or ankle. As you move your joint, the tendons and ligaments around them also move, and the noise you hear is simply that part of your body snapping into place.

The cause you should be worried about, however, is arthritis.

Sometimes joints crack because arthritis has developed and two rough surfaces are rubbing against one another - something that usually happens later on in life, once a lot of joint cartilage has been worn away. People who have this condition will experience pain along with the snapping sound, and the joints will become difficult to use.

It is often said that clicking or cracking your joints - particularly your knuckles - will trigger long-term problems such as arthritis. However, that simply isn't the case.

One man, Dr. Donald L. Unger, once set out to prove this. As a child, he as warned by his mother that he'd ruin his hands if he cracked his knuckles; so, like any good (and stubborn) scientist would do, he spent more than 60 years popping the knuckles on his left hand at least twice a day - but never touched the knuckles on his right.

In 1998, he published a paper on his experiment, and concluded there was no difference in function between his right and left hands. In 2009, when he was 83 years old, he won an Ignobel Prize for his findings, at which point he still claimed that all his knuckles were in perfect working order.

"I'm looking at my fingers, and there is not the slightest sign of arthritis in either hand," he said.

So, while popping noises in joints can sometimes be an indicator of a health problem, deliberately cracking a joint that's holding some tension is unlikely to actually cause a medical condition. Most of the time, any noise you hear from your joints is the result of perfectly normal movement or wear and tear, and you should only be concerned if you start to feel pain with it.