Do you crack your joints for the feeling of relief and greater motion in the involved joint?
Why Do Your Joints ‘Pop’?
The joints in our fingers are the easiest to crack, but many people also crack the joints in their neck, back and other joints. Most of the joints are synovial joints. The space between the two bones is filled with synovial fluid, which contains long and lubricating molecule like hyaluronic acid and lubricin, and lots of dissolved gas molecules. Its primary role is to cushion the bones.
To get a satisfying ‘pop’, you stretch the joint further than it normally goes, like bending your fingers. When you do that, the bones move away from each other, the space between bones gets larger, but the amount of synovial fluid stays constant. That creates a low pressure zone which allows dissolved gases to come out of the synovial fluid, just like the carbon dioxide fizzes out when the champagne is ready to be opened. The escaping gases form a bubble with a ‘pop’ in the joint. But the bubble does not last long, the surrounding fluid presses on it until it finally collapses. The bubble’s gases scatter throughout the synovial cavity and slowly dissolve back into the fluid over the course of 20 minutes. That is why it takes a while before you can crack the same joint again. It is called tribonucleation process.
Early on it was thought the ‘pop’ sound was associated with unhealthy joints, but as far back as the 1930’s scientists were showing that this also occurs in perfectly healthy joints.
Do Joints ‘Pop’ Lead to Arthritis?
No. Habitual knuckle popping or cracking is not associated with clinical or radiographic evidence of osteoarthritis. A researcher, who is also a physician, popped only the knuckles of his left hand, twice a day, for 50 years. He compared his hands at the end of the trial and found no arthritis in either hand and no visible differences.
However, attempting to ‘pop’ the knuckles can place an unnecessary stress that could eventually cause acute soft tissue injury, for example a partial tear of the ulnar collateral ligament of the thumb and subluxation of the extensor tendon of the fifth digit. Both injuries were associated with forceful manipulation of the digits.
Relationship between an Audible ‘Pop’ Sound during Spinal Manipulation and Its Clinical Outcomes
It has traditionally been thought that a ‘pop’ must accompany a thrust spinal manipulation to assure success of the particular technique applied. There have been several researches studied at whether adjustments with the popping sound indicated there were better outcomes for the patients being adjusted, but all these researches showed that they makes no difference whether or not there was a popping sound. All these meant that the clinicians adjusted the patients in a higher speed. We know that higher adjustment speed means you are more likely to get a popping sound. But this popping sound does not mean you will get better outcomes from your adjustment. Silent adjustment with an improvement in spinal function is just as good as loud popping one.
Clinicians should focus on patient centered outcomes rather than the presence or absence of a ‘pop’ when determining the benefits of thrust manipulation.
References:
1. Tye Powers, Gary Kelsberg, Sarah Safranek, Jon O. Neher. 2016. Clinical Inquiries. The Journal of Family Practice 65(10): 725-728.
2. Gregory N. Kawchuk, Jerome Fryer, Jacob L. Jaremko, Hongbo Zeng, Lindsay Rowe, Richard Thompson. 2015. Real Time Visualization of Joint Cavitation. Plos One 1-11.
3. Joshua A. Cleland, Timothy W. Flynn, PT, John D. Childs, Sarah Eberhart. 2007. The Audible Pop from Thoracic Spine Thrust Manipulation and Its Relation to Short-Term Outcomes in Patients with Neck Pain. The Journal of Manual & Manipulative Therapy 15(3): 143-154.
4. Marina G. Protapapas, Tyler C. Cymet. 2002. Joint Cracking and Popping: Understanding Noises that Accompany Articular Release. Clinical Practice 102(5): 283-287.