Is Knuckle Cracking Bad
The distinct pop and crack of knuckles being pulled and stretched is a familiar sound to many. You may not even realize how often you crack your knuckles until you consciously try to stop the habit. Up to 54% of people report regularly cracking their knuckles, whether for stress relief, simple habit, or just liking the sensation. But is this harmless fidgeting or is knuckle cracking bad for arthritis?
Anatomy of Knuckles
The knuckles are the joints that connect the bones of the fingers. Each finger has three joints called the distal interphalangeal (DIP), proximal interphalangeal (PIP), and metacarpophalangeal (MCP) joints 1. The thumb only has an MCP and DIP joint.
The MCP joints are where the main part of your hand meets your fingers, letting your fingers bend and straighten. The PIP joints are in the middle of your fingers, helping them to move too. The DIP joints are at the very end of your fingers and they let you bend the tips of your fingers. 2
The knuckles are covered by a special pocket of filled with a fluid. This fluid is called synovial fluid and it helps them move without any friction. There are strong bands called ligaments on the sides of the knuckles that keep them in place, and there are also protective plates in front of them. The finger bones are connected to the muscles of the hand and forearm by tendons, which help you move your fingers.
What Creates the “Cracking” Sound
The cracking or popping sound when knuckles are cracked is not caused by the bones themselves cracking, but rather by the gases being released from the fluid inside the knuckle joints. The current theory is that it is caused by the gases rapidly coming out of solution from the synovial fluid inside the joint capsules.
As Dr. Robert Klapper, an orthopedic surgeon at Cedars-Sinai Medical Center explains, “The noise of cracking or popping in our joints is actually nitrogen bubbles bursting in our synovial fluid” (source).
Similarly, according to a Scientific American article, “The cracking or popping sound is thought to be caused by the gases rapidly coming out of solution, allowing the capsule to stretch a little and decompress the joint” (source).
So in summary, the cracking sound comes from the release of gases from the joint fluid, not from the actual bones cracking or breaking.
Short Term Effects
When you crack your knuckles, you may experience some short term effects in the minutes and hours afterwards. One common sensation is a feeling of relief or release after cracking knuckles. This is likely due to the stretching and loosening of ligaments surrounding the joint during the cracking process.
Some research has found that immediately after cracking knuckles, grip strength can increase by up to 25% for a brief period. Castellanos and Axelrod (1990) measured hand strength before and after knuckle cracking and observed this temporary boost in grip force.
However, other short term effects are less beneficial. There may be some mild swelling and inflammation around the joint capsule after cracking. One study using MRI scans found more joint swelling in the knuckles of habitual knuckle crackers compared to non-crackers. This suggests frequent knuckle cracking could irritate the joint tissue.
Long Term Effects
The main question around knuckle cracking is whether or not it increases your risk of developing arthritis over time. There have been several key studies that have looked into this.
One study published in the Journal of the American Board of Family Medicine looked at 215 people ages 45-89 who had cracked knuckles on one hand for many years. They did not find any increased signs of arthritis on x-rays in the hand they cracked vs the one they did not.1
Another study followed 300 people over 50 years. Some were habitual knuckle crackers while others were not. But there was no difference in the incidence of arthritis between the two groups, leading the researchers to conclude knuckle cracking does not appear to increase arthritis risk.2
So the evidence indicates that knuckle cracking itself does not cause or worsen arthritis. However, a study in 1990 and 2018 did find that people who cracked knuckles frequently had more swollen hands and reduced grip strength compared to those who did not crack often. So while it may not directly lead to arthritis, habitual knuckle cracking can increase inflammation and impact hand strength and dexterity over time.
Other Risks
Although habitual knuckle cracking is generally harmless, there are risks with too forcefully or excessively cracking the knuckles. Cracking the knuckles with excessive force can potentially cause ligament or tendon injuries, though this is very rare. Sometimes it can it cause a finger to dislocate but this is very rare.
Additionally, the sound of knuckle cracking can be annoying or disruptive to those around you, especially if done frequently throughout the day. While not inherently dangerous, the noise and habit can be bothersome. According to a study cited by Harvard Health, knuckle cracking is associated with other habits like nail biting, smoking, and drinking alcohol 3.
Conclusion
Overall, research indicates knuckle cracking is not inherently dangerous or harmful when done in moderation. While the sound may be disconcerting, studies show it does not do damage to the joints or increase risk of arthritis. However, those who crack habitually and aggressively should exercise caution, as this can irritate the joints and tendons and lead to reduced grip strength.
Though not conclusively proven to be benign, cracking knuckles generally does not cause serious issues for most people. It appears to be more of an annoying personal habit than a major health concern. However, moderation is still advisable, as excessively forceful cracking could potentially injure joints and ligaments.
Medical Disclaimer
This information is offered to educate the general public. The information posted on this website does not replace professional medical advice, but for general information purposes only. There is no Doctor – Patient relationship established. We strongly advised you to speak with your medical professional if you have questions concerning your symptoms, diagnosis
