If you are like me, you will probably have been wondering about this for a long time, but never really got round to looking into it and satisfying your curiosity
The sensation and sound of joints clicking has a proper medical term – crepitus, and happens due to three main biomechanical reasons.
Gas Cavitation
Synovial fluid acts as a lubricant inside synovial joints in your body such as knuckles, knees, or fingers. This fluid that you have around the joints contains dissolved gases—mainly nitrogen and carbon dioxide.
When you stretch or bend a joint, you expand the joint capsule which has the effect of rapidly dropping the fluid pressure inside. This sudden drop in fluid pressure in the joint causes dissolved gas to form into a micro-bubble, which itself then collapses or forms rapidly. That sudden change in the state of the fluid in your joints is the sound you then hear.
Once a bubble forms, it takes roughly 15 to 30 minutes for the gas to dissolve back into the fluid before you can crack it again – hence why you cannot repeatedly ‘crack’ your joints no matter how hard you try – and trust me I’ve tried!
Tendons and Ligaments Snapping Over Bone
The tendons you have in your body act like rubber bands that connect muscle to bone. When a joint shifts position, a tendon can slide slightly out of place and snap back over a bony prominence. Unlike gas cavitation that I’ve just mentioned above, tendon popping can often be repeated immediately with every movement step or rotation
Rough Joint Surfaces or Cartilage Wear
As the cartilage in your body wears down as it does naturally over time, or becomes uneven, smooth joint gliding can turn into friction. This often sounds more like a grinding, crunching, or fine clicking rather than a single sharp pop that you may associate with typical joint popping that we all know well.
