Why do we crack our bones? The fluid in joints consists of carbon dioxide, nitrogen and oxygen. During bone crackling, their joint or they pop it, then they are stretching the joint capsules. Then, the gas is releasing in very short way which is forming bubbles. If you are feeling a pain when you are crackling your bones, then you should talk with your doctor.
Is it harmful the bone crackling? There are some studies in which is shown that people who are crackling their joints are not having side effects. Also there are some studies in which is shown that patients who are crackling their bones all the time, every day and as much as they can, and then this condition is causing serious damages to the soft tissue of the joints. If you are constantly crackling your bones, then this can lead to swelling and grip hand. If you want to crack some bone again, then you should wait until the gases are returned in the synovial fluid. This is condition which has not shown beneficial or harmful effects. In many cases this condition is not a reason for arthritis. When your bones are cracked, then the negative pressure is pulling the nitrogen gas temporarily in the joins which is not harmful. This is a topic on which there are not many studies. [1,2,3]
There are many studies about what our joints are crackling, but the exact reason for this condition is not known. We have said that this condition is not causing pain, but if you are repeating it constantly, then you have increased chances to get pain in your bones. When you are cracking your bones and you are feeling pain, then this means that you have some underlying abnormalities of the structures of your joints such as injured ligaments are loose cartilage. Some people who are suffering from bursitis, arthritis and tendinitis are noticing the crackling sounds due to their swollen and snapping tissues. We have asked ourselves why we are crackling our bones. Medical experts are saying that we are crackling them because the synovial fluid which is present in out joints is acting like a lubricant. People are thinking that when we are crackling our bones, then we have increased chances of getting arthritis while medical experts have not showed that bone crackling will cause serious disease to us. We are cracking many parts of our bodies such as jaws, back and neck vertebrae, toes, feet, hips, elbows, knees, Achilles tendon area, wrists, shoulders, ankles, sternum and feet. [1,2,3]
The physical mechanism which is causing a crackling sound as result of compressing joints, bending and twisting is not resolved. Here are some causes which doctors are saying that they can lead to bone crackling:
- Rapid stretching of ligaments
- Crackling sounds occur when bubbles form in joints as they are pulled apart
- Intra – articular (within – joint) adhesions being broken
- Cavitation within the joint – small cavities of partial vacuum form in the synovial fluid and then rapidly collapse, producing a sharp sound
There are many studies which are done about this topic and who try to figure out which is the real cause for the bone crackling. Synovial fluid cavitation has taken part of these theories. In the recent studies is shown that people who are crackling their bones are hearing crackling sounds when the bubble in their joints is formed not when it collapses. Also there are some studies in which 215 people were regulated for their bone crackling. People were between 50 and 89. In this study there were two groups.  In the first one are people who are crackling their bones while in the second one are people who are not crackling their bones. In this study it was shown that bone crackling has not connection with hand osteoarthritis no matter how many years people were crackling their bones. Also there was earlier study that there is connection between arthritis with people who are chronic crackers. In this study it was shown that people who were cracking their hands constantly were having lower grip strength and increased hand swelling. But also this habit can come from other parts of our life such as drinking alcohol, smoking and biting of the nails. Also there was a study which was done by Donald Unger which is medical doctor. In this study he was crackling his left hand every day more than six years while the right hand was not crackled. He has not noticed arthritis or other serious disease with his hands. 
 Stinson A. What to know about popping joints. Medical News Today. 2019. Retrieved from medicalnewstoday.com/articles/325341
 Castellanos J, Axelrod D. Effect of habitual knuckle cracking on hand function. Annals of the Rheumatic Diseases. 1990;49(5):308–9.
 Protopapas MG, Cymet TC. Joint cracking and popping: Understanding noises that accompany articular release. The Journal of the American Osteopathic Association. 2002;102(5):283-7.
 Deweber K, Olszewski M, Ortolano R. Knuckle cracking and hand osteoarthritis. Journal of the American Board of Family Medicine. 2011;24(2):169-74.
 Moynihan Q. A doctor cracked his own knuckles for 60 years to prove it doesn’t cause arthritis. Business Insider. 2018. Retrieved from www.businessinsider.com/doctor-cracked-own-knuckles-for-60-years-to-quash-links-with-arthritis-2018-8