You’ve most likely heard the phrase, “Don’t crack your knuckles or you’ll get arthritis.” This may have stopped you for the time being, but when no one was around, you probably went right back to it.
But does the saying hold any truth, or is it just an old wives’ tale? Are we causing ourselves long-term harm by giving our knuckles a good crack?
While there hasn’t been extensive research on the topic, you may be able to rest easy (and enjoy your cracking) after hearing about the study findings. So, for all of you knuckle crackers, have yourself a good read, because this one’s for you.
What exactly is going on in our hands when we crack our knuckles? Well, for starters, you’re not actually cracking anything. The cause is not definitive, but one theory is gas movement: Imagine a Champagne bottle that’s been shaken. Once the cork has been popped, all those bubbles come rushing up to create an explosion. This is similar to what is going on in your knuckles. What you’re hearing is gas moving from the spaces in between your joints. This gas starts off as small bubbles in the connective fluid within our joints; when the gas in the bubbles is pushed out, it creates larger bubbles that pop. Once this gas is released, it takes about 15 minutes or more for the joints to go back to their normal size. That’s why you can’t crack the same knuckle twice right away.
Why do we do it anyway? Cracking our knuckles can offer some relief from stiffness, as we are stretching the joint and also stimulating the nerves, which can last up to about 30 minutes. In fact, people can crack several joints in their bodies, including the hips, wrists, elbows, back and neck vertebrae, toes, shoulders, feet, jaws, ankles, and Achilles tendon. Foot cracking can be a great part of a therapeutic foot massage!
What causes that satisfying crack when we press on our knuckles? According to the Library of Congress, the popping noise associated with cracking your knuckles actually comes from a combination of escaping gases, the movement of joints, tendons, and ligaments, as well as rough surfaces. The liquid between the bones and cartilage in our joints is called synovial fluid, and it works as a lubricant. This fluid is full of gases like oxygen, nitrogen, and carbon dioxide, and when you crack your knuckles, the gas bubbles in the fluid pop and release that familiar sound. This is why you can’t crack the same knuckle twice in succession, as the gas needs time to build up once again after being released.
When you crack your knee or ankle, the sound produced is usually due to the movement of a tendon or ligament. Each time you move a joint, the position of the tendon changes slightly and can create a cracking sound when it snaps back in place. Similarly, ligaments can tighten with joint movement, also producing a cracking sound. Finally, if you already suffer from arthritis in your knuckles and other joints, the rough surfaces and absence of cartilage can result in audible cracking and snapping sounds.
Notable research on the topic comes from a California doctor and allergist who conducted the study on himself. Over a 60-year span, Dr. Donald Unger defied his mom’s advice and cracked the knuckles on his left hand twice a day—and never his right.
After six decades observing both his hands, he concluded that there was no sign of arthritis on his left hand. The research, although anecdotal, landed Dr. Unger an Ig Nobel Prize for Medicine in 2009; Ig Nobel Prizes are the acclaimed parody of the Nobel Prize, awarded to scientists for “achievements that first make people laugh, then think.”
Research conducted in 1975 in Los Angeles examined 28 residents of a nursing home. Residents who were habitual knuckle-crackers were less likely to develop osteoporosis within their hands. To further confirm the findings, the hands of the participants were X-rayed.
The orthopaedic experts at Johns Hopkins agree that the cracking and popping sounds from knuckles or other joints are nothing to worry about. Whatever the cause, these sounds don’t require treatment, nor do they lead to future problems. They also state on their public service website, “There is no basis for the admonition to not crack your knuckles because it can lead to arthritis. There are no supplements or exercises to prevent these noises.”
The only time to worry about cracking or popping of a joint is if there is pain when the joint pops, or if it swells. If the joint gets locked or stuck when it pops or cracks, then see your doctor—this might be a joint problem. If you are losing motion or function of a joint, then seek medical treatment.
You may still be wondering where the idea of arthritis being linked to knuckle cracking originated? It’s hard to truly tell where most myths originate, but it may have to do with arthritis sufferers noticing their joints cracking. Nowadays, the causes of arthritis are better understood—joint inflammation linked to the natural wear and tear on the cartilage, family history, and previous injuries.
Although the clinical evidence is sparse, it’s safe to say you won’t develop arthritis through cracking your knuckles. So, if you’re still on the fence whether to crack or not to crack, go with whatever feels good.