What causes knuckles to making popping sounds?

The video explains how gases in synovial fluid expand and burst, causing a popping sound when knuckles are cracked. This process stimulates nerves and relaxes muscles, often increasing mobility. It takes about 25 minutes for gases to rebuild in the synovial fluid before knuckles can be cracked again.

What sound is produced when gasses in the joints burst?

Describe the relationship between muscle relaxation and mobility.