Myth, checked
Does Cracking Your Knuckles Cause Arthritis?
There was no arthritis in either hand; his cracked hand was just as healthy as the one he'd left alone. Decades of other studies agree: there is no link between the habit and the disease.
The Case of the Pop
That pop in your knuckles. Is it really arthritis waiting to happen? Everyone has an opinion, and almost everyone has been warned. But here's the clue that unravels the whole case: the sound isn't what you think it is.
That sharp crack isn't your bones grinding together. It’s not bone on bone at all. The sound is coming from the space between your joints. And it's the sound of a bubble being born, and then dying, in an instant.
Your joints are lubricated by a thick liquid called synovial fluid. It's like oil for your body's hinges. When you stretch your finger, you pull the joint apart. This creates a tiny, low-pressure vacuum in the fluid.
That vacuum pulls dissolved gases out of the fluid, forming a bubble. The crack is the sound of that bubble collapsing. Once it's popped, the gases have to dissolve back into the fluid. That's why you can't immediately crack the same knuckle again.
The Sixty-Year Experiment
The biggest clue in the case against knuckle cracking comes from one doctor. For sixty years, Donald Unger cracked the knuckles on his left hand. At least twice a day. He left his right hand alone. A perfect, lifelong experiment on himself.
The assumption is that all that cracking would wear the joint down. That it would lead directly to arthritis. After six decades of daily cracking on one side, and total peace on the other, the evidence was in. What do you think the X-rays showed?
There was no arthritis. In either hand. His cracked hand was just as healthy as the one he'd left alone. Decades of other studies agree: there is no link between the habit and the disease. Save this for the next scolding.
The Real Culprits
The pop in your knuckles has been cleared. So what *does* cause arthritis? The culprits aren't in your hands. The main suspects are your age, genetics, and past injuries to the joint. Notice what's not on the list.
Being cleared of arthritis doesn't mean the habit is completely harmless. It's just not a criminal mastermind. Some studies suggest habitual crackers might end up with slightly weaker grip strength, or some soft tissue swelling. A minor offense, not a major one.
The case is closed. That pop is a gas bubble, not your future pain. It won't give you arthritis. The only real damage might be to the patience of people nearby. So, are you a cracker or a hater?
Every claim, checked
This is the whole list — including the ones we could not confirm. How this works is written down in how we check things.
The crack is the sound of a bubble being born, and then dying, in an instant (i.e., caused by bubble collapse).UnverifiedKawchuk et al. 2015, PLOS ONE; Unsworth et al. 1971, Nature
For sixty years, Donald Unger cracked the knuckles on his left hand at least twice a day and left his right hand alone as a self-experiment.VerifiedUnger, D.L. 'Does knuckle cracking lead to arthritis of the fingers?' Arthritis & Rheumatism, 1998; Ig Nobel Prize 2009
There was no arthritis in either hand; his cracked hand was just as healthy as the one he'd left alone.VerifiedUnger, D.L., Arthritis & Rheumatism, 1998
Decades of other studies agree: there is no link between the habit and the disease.VerifiedCastellanos & Axelrod 1990, Annals of Rheumatic Diseases; Deweber et al. 2011, Journal of the American Board of Family Medicine
The main causes of arthritis are age, genetics, and past injuries to the joint.VerifiedCDC; Arthritis Foundation
Some studies suggest habitual crackers might end up with slightly weaker grip strength, or some soft tissue swelling.VerifiedCastellanos & Axelrod 1990, Annals of Rheumatic Diseases
Joints are lubricated by synovial fluid, and stretching a finger creates a low-pressure vacuum in the fluid.VerifiedKawchuk et al. 2015, PLOS ONE
After popping, gases have to dissolve back into the fluid, which is why you can't immediately crack the same knuckle again.VerifiedKawchuk et al. 2015, PLOS ONE
People also ask
What makes the sound when you crack your knuckles?
The popping sound is not from your bones. When you stretch a joint, it creates a vacuum in the joint fluid which pulls out dissolved gases, and the sound is a bubble collapsing.
Why can't you crack the same knuckle twice in a row?
You cannot crack the same knuckle again right away because the gases that formed the bubble need time to dissolve back into the joint fluid. Only after they have dissolved can a new bubble be formed and popped.
What does cause arthritis?
The main risk factors for arthritis are not related to habits like knuckle cracking. The primary causes are a person's age, their genetics, and any previous injuries to the joint.
Are there any other side effects from cracking knuckles?
While knuckle cracking is not linked to arthritis, some studies suggest it may have minor negative effects. Habitual cracking might lead to weaker grip strength or swelling in the soft tissue.
One myth a week, redrawn.
One email per video: the myth, what's actually true, and links to the research. No spam, unsubscribe in one click.