Popping joints are common. Some researchers used to think the popping sound was an air bubble between collapsing bones, while others believed the sound came from the recoil of muscle ligaments.
Doctors call popping joints crepitus. Many people dislike the sound of popping or cracking joints, even though healthy joints can make noises. One 2017 study showed that popping joints made people experience negative thoughts, emotions, and even avoid healthful activities.
Although popping joints are harmless in most cases, in some instances, they can be a symptom of a medical condition.
The exact reasons and causes of joint popping are still under debate.
More recently, in a 2015 study, researchers using MRI technology were convincingly able to show that joint popping and cracking is not the release of an air bubble but the creation of a small space between bones. Doctors call this tribonucleation.
More research into the exact process behind popping joints is still necessary, however.
Understanding joint popping
To date, there is no evidence to suggest that popping a person's own joints has negative effects, only a slight increase in range of motion.
When talking about popping joints, professionals differentiate between a person physically popping their own joints and condition-related popping.
If there is pain, swelling, limited range of motion, or a history of injury, the popping could have some links to a more serious health condition.
Popping with a link to a health condition generally occurs more frequently and can be painful.
Physical popping has no pain and is not a cause for concern.
Some conditions cause popping joints to happen more frequently, such as in some forms of arthritis.
As arthritis progresses, popping can become more frequent.
Osteoarthritis (OA) causes the cartilage in a joint to become thinner and more ragged. This thinning and wear can cause pain as joints rub against each other, and it also has links to popping joints. Popping joints occur more frequently as OA progresses.
A 2018 study found knee popping to be a predictive factor in people who have OA without symptoms. For those who had OA and knee popping, they were more likely than those without knee popping to have other symptoms with their OA.
Another study suggests that people with OA who also have popping knee joints were more likely to report lower physical function and knee-related quality of life.
People should always treat self-reported findings with caution.
As mentioned above, other studies show that people dislike joint popping and associate it with unhealthy joints, and so this feeling may influence self-reported findings.
Popping joints can also occur with forms of inflammatory arthritis, such as rheumatoid arthritis.
High-pitched popping sounds from joints are more likely to be from inflammatory arthritis. Lower sounds can be from either inflammatory or noninflammatory arthritis, although this may be hard to distinguish.
Inflammation around tendons
There is currently no evidence to suggest that regular knuckle cracking causes injury to joints. In some rare cases, knuckle cracking may result in dislocation or thickening over a joint, which is known as a knuckle pad.
In one old study from 1990, 74 participants who regularly cracked their knuckles had a joint injury. There was no difference in cases of arthritis between the knuckle cracking group and the control group.
A more recent 2017 study assessed the finger joints of 40 people, including 30 who habitually cracked their knuckles. The researchers found no adverse effects of knuckle cracking. They did find that the habitual knuckle crackers had slightly more range of motion.
Some medical professionals manipulate a person's joints, and this can result in a popping noise.
During a chiropractic adjustment, the practitioner uses pressure to help realign joints that may be somewhat out of alignment but not dislocated.
This realignment may or may not involve a popping noise. There is no evidence that a popping joint indicates a more successful alignment. It simply occurs as a side effect of the pressure applied.
Typically, popping joints are not a cause for concern.
It is important to differentiate between joint noise with pain and swelling and joint noise without pain. Joint noise without pain is very normal, common in healthy joints, and generally not a cause for concern.
People should see a doctor if they are experiencing popping joints with pain.