What are the cracks that I can hear in my knees, shoulders and knuckles etc?
There are two ‘cracking’ sounds that can come from the body: (i)a joint separations, and (ii)a tendon flicks.
Joint Cracks
Joints have a fluid called ‘synovial fluid’ in them, and they are airtight. If you separate the two surfaces in opposite directions there is some resistance (like trying to separate two sheets of glass stuck together with water between them) but if/when it gives, there can be a crack. This is gas being released from the synovial fluid in the vacuum. If you crack your knuckles, or hear a crack in your knees when you crouch down, this is usually the cause of the crack.
These types of cracks are normal and natural if you hear them every now and then. But try not to get in the habit of trying to crack your own joints. Chiropractors often release joints in this way but this is to increase the movement of specific joints that are not moving enough. What happens when a chiropractor cracks your back?
Tendon Flicks
The other type of noise you can hear is simply tight muscle tendons catching slightly on a bony prominence as you move and then suddenly flicking free. It can create a crack similar in sound to a joint crack. This is much more likely in the muscles are a bit tight.
Joint cracks can only happen once in about every ten minutes because it takes a while for the vacuum to reform in the joint. Tendon cracks can happen multiple times in a short period of time. (Eg. Every time you move a joint.) This is one way of telling which type of crack it is.
Why does my neck crunch when I roll my head?
Both Joint Cracks and Tendon Flicks can happen when you roll your neck, but this doesn’t mean rolling your neck is good for you! When you roll your neck, some joints can be separated enough to cause joint cracks. If the joint is restricted, this can be a good thing. If the joint is already moving too much, it can make the joint move excessively.
Rolling your neck can move joints in a way that causes them to jam up too, so it isn’t recommended. A better way to stretch and mobilise the neck is simply stretching it from side to side (IE. Moving your ear towards your shoulder while facing forward the whole time.)
Stefan Becker
Barcelona Chiropractor