Does cracking your knuckles cause arthritis?
One of the most repeated warnings in medicine has little evidence behind it. What the studies of habitual knuckle crackers found — and what the 'pop' actually is.
The verdict
“Cracking your knuckles causes arthritis”
D · UnsupportedEvidence at a glance
| Claim | Grade | Refs |
|---|---|---|
| Cracking your knuckles causes arthritis | D · Unsupported | 1, 2, 3 |
| Habitual knuckle cracking is not linked to hand arthritis in observational studies | B · Moderate | 1, 2, 3 |
| The cracking sound involves a gas bubble forming in the joint | B · Moderate | 2 |
Grades follow our method. A strong link between two things is not proof that one causes the other.
Key points
- In a study of 215 people aged 50 to 89, hand arthritis was about as common in knuckle crackers as in people who did not crack their knuckles.
- Even decades of cracking, and how often people did it, were not linked to arthritis in the joints they cracked.
- Reviews of the literature agree: observational studies have failed to show a link.
- The pop involves a gas bubble forming in the joint fluid; exactly how the sound is made is still debated.
Almost everyone has been told, usually by a relative, that cracking your knuckles will give you arthritis. It is one of the most repeated health warnings there is. It is also one of the easiest to check, because so many people crack their knuckles for decades.
What the studies found
In one study, researchers asked people aged 50 to 89 who had had a hand X-ray in the previous five years about their knuckle-cracking habits — how often, for how long and which joints. Among 215 respondents, about one in five cracked their knuckles. Arthritis in any hand joint was found in 18.1% of knuckle crackers and 21.5% of non-crackers, a difference that was not statistically meaningful. Looking joint by joint, cracking was not a risk factor for arthritis in the joints people actually cracked, and neither the number of years nor the total amount of cracking made a difference.[1]
That fits the wider literature. A review of the anatomy and clinical research concluded that the evidence on knuckle cracking and arthritis comes mainly from observational studies, and that these have failed to show an association.[2] A clinical evidence summary reached the same answer: habitual knuckle popping over several decades is not associated with clinical or X-ray evidence of arthritis.[3]
So what is the pop?
Researchers agree that a gas bubble forms in the fluid inside the joint as the joint surfaces are pulled apart. Exactly how the bubble forms, and what produces the sound, is still debated.[2] What it is not, on current evidence, is the sound of cartilage wearing away.
The honest caveats
These are observational studies, mostly modest in size, and nobody has randomly assigned people to crack their knuckles for 40 years. That is why "knuckle cracking is not linked to arthritis" is graded B rather than A. But the claim that cracking causes arthritis has no good evidence behind it, and is graded D.
If a joint is painful, swollen or stiff, or if cracking comes with pain, that is a different situation from a painless habit — and worth getting checked.
References
- deWeber K, Olszewski M, Ortolano R. Knuckle cracking and hand osteoarthritis. J Am Board Fam Med. 2011;24(2):169-174. doi:10.3122/jabfm.2011.02.100156
- Rizvi A, Loukas M, Oskouian RJ, Tubbs RS. Let's get a hand on this: Review of the clinical anatomy of "knuckle cracking". Clin Anat. 2018;31(6):942-945. doi:10.1002/ca.23243
- Powers T, Kelsberg G, Safranek S. Clinical Inquiry: Does knuckle popping lead to arthritis? J Fam Pract. 2016;65(10):725-726. PubMed 27846331