Why do joints crack

Some people love to crack their joints. Most often on the fingers, toes and spine. Other people can't stand this sound. There are people who believe that cracking joints leads to osteoarthritis. But why do joints crack at all?

The road to solving the mystery of joint cracking was very long. It lasted for many decades and the final consensus in detail has still not been reached. As early as 1938, it was proved that it is possible to crunch a large part of the joints in the body. In 1947, researchers used X-rays to study it and concluded that cracking occurred when a gap between the joints suddenly formed. They thought there would be a rapid decrease in synovial fluid pressure and cavity formation.^[1]

Researchers in 1971 disagreed with the theory of cracking during cavity formation, believing that sound was generated when the cavity collapsed. In 2015, however, it was discovered that gas bubbles remain in the synovial fluid even after cracking, which is more in line with the original assumption that sound generates bubble formation. Shortly afterwards, in 2018, a mathematical simulation was performed which indicated that the bubbles occurring after the crack are only a result of a partial collapse, and that the crack itself is the result of that collapse.^[2]

Whether it is the formation or collapse of gas bubbles, for us ordinary mortals, it is essential that sound produces a sudden change in the dynamics of the gas. Specifically, they are carbon dioxide, oxygen and nitrogen. Gas recovery and the possibility of re-cracking takes about 15 to 20 minutes. More importantly, however, the finding that joint cracking most probably does not cause any disease, such as osteoarthritis, has been scientifically studied several times.^[2]