Some people have a compulsive habit of overstretching their knuckles until they crack, every few minutes. This can be extremely annoying for other people.
The important questions are whether you can do permanent damage to your fingers and why knuckle cracking seems to be so addictive:

 

There is something immensely satisfying about overstretching the ankles to the cracking sound. If the compulsion to crack is suppressed, people with this habit feel nervous and irritable. Unfortunately, people are gradually driven mad by the constant cracking and it is not uncommon to be criticised. Some even say that the regular cracking of the knuckles can lead to arthritis. In this respect, the all-clear can be given to those affected, as there is no evidence that constant cracking and overstretching of the knuckles causes physical damage. People with arthritis in their hands have been knuckle crackers and non-knuckle crackers.
However, the permanent and compulsive cracking can lead to slight discomfort in the finger joints. Occasionally, swelling, joint weakness and temporary injuries occur.

Why is this habit so addictive? There is no clear scientific explanation as to why such a compulsion develops, but one theory is that it releases nervous energy. Just as some people twirl their hair and others tap their feet, there are those who crack their knuckles. Once you have started cracking your knuckles, it gives many people a good, physically liberating feeling and, conversely, they feel discomfort until they have cracked their knuckles.

The cracking sound you hear when you overstretch your finger joints is caused by air bubbles in the synovial fluid, which are burst by the pressure, not unlike a blister film.

How do you wean yourself off cracking your knuckles?

To get rid of this annoying and disruptive habit, as with any compulsive disorder, you should confide in a friend and ask for their help. Other people can draw the person's attention to the fact that they are unconsciously stretching their fingers again. Other outlets should be sought for the release of nervous energy. Physical exercise helps in most cases. If you catch yourself in the habit, you need to distract yourself. It takes about four weeks for a habit to form, and it can take just as long to get rid of it.