Why do your knuckles pop?

The kids were all hooked on television as the finale between the two best football teams was going .  Suddenly Suti started making some noise. The children were irritated and they started scolding her. But on observering they saw that this sound  was being produced by suti on cracking her fingers. Everyone was amazed and they thought it as some kind of magic. They asked Mrs Payala (caretaker) about this.

So Mrs Payala with a smile on her face agreed to share with the little ones about this MAGIC.

Not a magic :

The crackling sound  is not due to some kind of  mystical spell instead its  produced due to the bending of joints.

There are lots of explanation regarding this. According to some experts this sound is produced due to stretching of ligaments or grinding of bones against each other.

Widely accepted View:

The most comman clarification given is that the sound is due to bubbles in the joints. We have seen that this popping sound is not only produced on bending fingers but also on bending wrists, hips and shoulders. All these joints are called synovial joints

Synovial Fluid:

The space between the two bones is filled with viscous liquid called synovial fluid that has long lubricating molecules like Hyaluronic acid and Lubricin.

The main function of this fluid is ease the movement of the bones . It also contains phagocytic cells which helps in cleaning any bone or cartilage debris that ends up in the joint.

Knuckle cracking sound:

The synovial fluid like other body fluids contains lots of dissolved gas molecules.

When we bend our bones or stretch them the space between the bones  increases but the synovial fluid remains constant. This creates a low pressure zone and pulls the dissolved gases out of synovial fluid. The escaping gases form a bubble with a pop.  But within sometime the bubbles collapse and dissolve back into fluid.

Wrong perception:

A lot of people believe that cracking knuckles cause Arthritis. To disaprove this, Dr. Donald Unger cracked knuckles of his left hand repeatedly for 50 years. Even after such a long time both hands of  Dr.Donald were Arthritis free. For this selfless act he received Ig Nobel Prize .

The End

At the end when the kids learnt that the sound being produced by Suti was no magic, they all started laughing and cracking their fingers.

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