Causes
To deliberately produce the clicking sounds, many people bend their fingers into unusual positions. These positions are usually ones that their own muscles are unable to achieve. However, cracking a joint that has been exercised recently is generally recognised to be palliative. For example, bending a finger backwards away from the palm (into extension), pulling them away from the hand (abduction), compressing a finger knuckle toward the palm (into flexion), or twisting a finger about (torsion).
The snapping of tendons or scar tissue over a prominence (as in snapping hip syndrome) can also generate a loud snapping or popping sound.
Read more about this topic: Cracking Joints