Cracking your knuckles causes arthritis
The common belief that habitually cracking knuckles causes arthritis has been tested in multiple studies, including a decades-long self-experiment by a physician, and none have found a meaningful association between knuckle cracking and arthritis development.
What we know
The popping or cracking sound produced when a person pulls or bends a finger joint has been studied by biomechanics researchers for decades, and the current scientific consensus attributes the sound to the formation and rapid collapse of a gas bubble within the synovial fluid that lubricates the joint, a phenomenon called tribonucleation, confirmed through real-time MRI imaging in a 2015 study published in PLOS ONE that directly visualized bubble formation coinciding precisely with the audible crack. This settled a long-standing scientific debate over whether the sound came from bubble formation or bubble collapse, though it did not change the separate and more practically relevant question of whether the underlying joint mechanics involved cause any lasting damage.
The belief that this habit causes arthritis appears to stem from an intuitive but unsupported assumption: if a joint makes an unusual noise, repeated over years, it seems plausible that some cumulative damage is occurring. This assumption has been tested directly. Perhaps the most widely cited piece of evidence is an informal but genuinely documented self-experiment conducted over more than 60 years by physician Donald Unger, who cracked the knuckles on one hand several times a day while leaving the other hand uncracked as a control, and found no difference in arthritis development between his two hands, a result he published in a short paper in Arthritis and Rheumatism in 1998, for which he was later awarded a satirical Ig Nobel Prize in 2009 recognizing research that makes people laugh and then think.
Beyond this well-known single case, larger formal epidemiological studies have examined the question in bigger populations. A study published in the Journal of the American Board of Family Medicine in 2011 surveyed nearly 300 people, comparing habitual knuckle crackers to non-crackers, and found no significant difference in the prevalence of arthritis between the two groups, though the same study did find habitual crackers had a somewhat higher prevalence of hand swelling and lower average grip strength, suggesting the habit may not be entirely without any physical correlate even though it does not appear linked to arthritis specifically. Other smaller studies from the 1970s through 1990s produced generally similar findings, with occasional outlier results attributed to small sample sizes and inconsistent definitions of both 'habitual cracking' and 'arthritis' across different studies, a common limitation researchers note when comparing this body of literature.
Medical organizations including the Arthritis Foundation state clearly in public patient guidance that no scientific evidence links knuckle cracking to arthritis, and rheumatologists explain that osteoarthritis, the most common form of arthritis, develops through cartilage breakdown linked to factors including age, genetics, joint injury, and repetitive mechanical loading under load-bearing conditions very different from the brief, low-force joint distraction involved in cracking a knuckle. The habit is not entirely without any downside; a small number of case reports describe soft tissue injury or reduced grip strength associated with very frequent, forceful cracking, but these are distinct from arthritis and represent a much narrower and less common concern than the popular belief suggests.
The myth's persistence likely reflects a broader pattern in folk medical beliefs, where an unusual bodily sound or sensation gets linked to a chronic condition through plausible-sounding but ultimately untested reasoning, which then gets repeated across generations as established fact even after direct experimental tests, including one spanning six decades, have failed to find supporting evidence.
Common claims
- Cracking your knuckles causes arthritis.False, multiple studies including a 60-year self-experiment found no association.
- The cracking sound comes from a gas bubble forming in the joint fluid.True, confirmed by real-time MRI imaging in a 2015 study.
- Habitual knuckle cracking has no physical effects at all.Partly false, one study found associations with hand swelling and reduced grip strength, though not arthritis.
- Osteoarthritis is caused by age, genetics, and joint injury rather than joint noises.True, this reflects the established medical understanding of osteoarthritis development.
Evidence hierarchy
All sources
- Does knuckle cracking cause arthritis?Arthritis Foundation · 2023
- Real-Time Visualization of Joint CavitationPLOS ONE · 2015
- Knuckle cracking and hand osteoarthritisJournal of the American Board of Family Medicine · 2011
- Does knuckle cracking lead to arthritis, a 60-year self-experimentArthritis and Rheumatism · 1998