This will sound weird, but... Have you ever stabbed a big piece of meat with a thick knife? And you know the sort of sucking sound it makes when you extract you

This will sound weird, but... Have you ever stabbed a big piece of meat with a thick knife? And you know the sort of sucking sound it makes when you extract your knife from the meat? This is similar to what's happening inside your knuckles. The sudden in-rushing of gas into the space between your knuckles.