People often ask me, "Am I going to get arthritis because I crack my knuckles?" This topic is controversial even among medical professionals.1 Research gives us some insights.
How knuckles crack
Located where the fingers meet the hand, knuckles are sometimes called metacarpophalangeal joints (MCPs).
- The clicking, cracking, popping, or snapping that occurs when you crack your knuckles is associated with tiny gas bubbles.
- To produce a cracking sensation, a finger is forced forward or backward (doctors call this hyper-flexion or hyper-extension at a metacarpophalangeal joint) or pulled straight away from the hand. Any of these movements can cause a change in pressure in the joint. The pressure change causes tiny gas bubbles to form in the knuckle’s joint fluid.
- It is not clear whether the cracking noise is produced when bubbles form or when the bubbles pop.2
- It usually takes 15 or 20 minutes for the gas bubbles to dissipate and for the bones of the joint to return to their normal positions.3 This is why you can’t crack the same knuckle twice in a row.
It seems logical that habitual knuckle cracking causes arthritis or other degenerative changes in the hand. But what do medical researchers say?
Conflicting research on knuckle cracking and arthritis
Research studies comparing knuckle crackers' to non-crackers have had mixed results.1 A couple of studies have reported an association between knuckle cracking and hand arthritis.4,5 Others found no significant connection.6,7
So, is it okay to continue your knuckle cracking? Well, I wouldn’t recommend it. Even studies that found no connection between knuckle cracking and arthritis reported other signs of joint changes.1,7,8
Possible changes in the hand
Research suggests people who often crack their knuckles may have:
- More swelling in their hands7
- A weaker grip7
- A slightly larger range of motion in their hands8,9—while this seems like a good thing, hypermobility can put a joint at risk of osteoarthritis and other injuries
- Signs of cartilage changes in their knuckle joints that indicate possible scarring and a higher risk of developing osteoarthritis1
Like the research regarding knuckle cracking and arthritis, the research regarding these potential effects also sometimes conflicts. For example, the same study1 that reported knuckle crackers had cartilage changes did not find they had weaker grip strength.
Studies examining knuckle cracking tend to be small, ranging from 35 to 300 people. Also, most compare knuckle crackers and non-crackers at a single point in time. Larger, longer-term studies that measure changes in hands over time are necessary to draw more clear conclusions.
Other habits associated with knuckle cracking
One research study of 300 people reported that people who cracked their knuckles were more likely to have manual labor jobs and smoke.7
Manual labor can be a risk factor for osteoarthritis. If you have a manual labor job, finding ways to reduce daily stress on your joints may be more important than quitting knuckle cracking to lower your risk of arthritis.
Likewise, quitting smoking or other nicotine use can reduce your risk of serious medical problems, including lung cancer, heart disease, stroke, and chronic obstructive pulmonary disease (COPD).