Snap, Crackle and Pop

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Our joints make a variety of noises. This article describes the cause of some of them.

 

Snap

The kneecap (patella) is a lens-shaped bone embedded in the tendon of the quadriceps femoris. On its underside is a ridge which articulates with the thigh bone (femur). As the knee bends and straightens, the patella slides within a slot on the femur called the trochlear groove. The patella moves in many directions within this groove to provide efficient, frictionless movement.

Structural alignment and muscular weakness or imbalance may cause the patella (kneecap) to track improperly on the femur (thigh bone) during movement, leading to pain around the kneecap. When the patella slips back into its groove there is a loud “snap”. This typically happens when the knee is bent.

 

Crackle

The crackly noise many of us hear when we move our head is called crepitus. It can occur in any of the synovial joints and is caused by bone rubbing against bone or roughened cartilage when an arthritic joint is moved.  Perhaps it should be called decrepitus!

Pop

Sometimes our joints make a popping sound when we move them. This seems to be more common in the autumn and early winter. I have spent some considerable time trawling the web without finding an explanation. There's a lot out there about cracking your finger joints (generally accepted to not be a good idea) and also about joint pain increasing with a drop in air pressure and increase in humidity (no agreement as to how or why but a widespread explanation is that a change in atmospheric pressure causes the synovial fluid to expand and press against pressure sensors in the joint which the body then senses as pain).

Based on the little snippets of information I gleaned here and there, putting two and two together and hopefully making four, this is my explanation of what is happening when we hear a popping noise in a joint. When atmospheric pressure drops, the pressure within the synovial fluid drops and gases that were in solution in the fluid come out of solution and form a gas bubble. Any sudden increase in pressure e.g. from bending a joint, causes caviation, the collapse of the gas bubble, which is accompanied by the familiar popping sound. The same process happens when someone deliberately cracks their finger joint only there it is the pulling apart of the bones that causes the decrease in pressure and bubble to form. In the same way that you cannot immediately crack your fingers again so it is with your knees and other joints. After caviation has occurred it cannot happen again until another bubble has formed.

 

... and Clunk

For some of us certain movements always cause a clunking sound. This is called by tendon friction rub. The sound is made by a tendon or other fascia rubbing against bone. Lying on the back on the floor and circling one leg results in this clunking sound in many people.

 

Yoga has many exercises for the maintenance of healthy joints including the pawanmuktasana series of exercises from the Bihar School of Yoga (described in Asana, Pranayama, Mudra and Bandha by Swami Satyananda) and Swami Rama’s joints and glands exercises (outlined in his book Exercises for Joints and Glands: Gentle Movements to Enhance Your Wellbeing)

 

Regular performance of such exercises may help delay the onset or slow the progression of degenerative conditions such as arthritis, rheumatism or stiffness and help counter muscular imbalances.

 

 

This article is extracted from a post that appeared on Anne’s Yoga Blog on 2^nd November 2009

http://yogawithanne.blogspot.com/2009/11/snap-crackle-pop.html