You’ve heard it all before: Someone cracking knuckles in a meeting, or the snap, crackle and pop of joints in nearby cubicles as coworkers bend backs, flex elbows or stretch necks.
You might even hear the unmistakable snap from your ankles or knees as you walk from the bedroom to the kitchen in the morning.
So, what’s up with all that noise? UVA Today asked Susan Saliba, a professor in the University of Virginia’s School of Education and Human Development and co-director of the Exercise and Sports Injury Laboratory, why joints get noisy and what to do, or not do, about them.
Q. What makes your joints crack, crinkle and clatter?
A. There are two types of snapping and popping.
One is like cracking your knuckles. There are microscopic gas bubbles within the synovial or joint fluid, and when the joint is “distracted,” the suction creates a negative pressure, and the gas bubbles consolidate and “pop.”
Susan Saliba is a professor in the UVA School of Education and Human Development and co-director of the Exercise and Sports Injury Laboratory. (Photo by Lathan Goumas, University Communications)
Lots of joints pop. Often, it relieves pain and pressure around a joint temporarily. If you’ve ever baked a cake, you gently slam the pan to consolidate and pop the gas bubbles to make the cake smooth, a process called cavitation. Cavitation in the joint takes pressure away from joint receptors, and almost immediately, there is a sense of relief.
The other type of noise is friction. We’re designed to have bursae – synovial fluid-filled sacs – over bony projections to allow gliding and sliding. But just like a blister, frictional overuse makes the structure produce more fluid and sprains and strains make tendons and bursae swell.
We may feel the friction, but who wants to stop running before finishing the workout, or stop painting or washing your car before it’s done? So, we keep going, and the bursa swells, and now there’s limited space. It may not hurt after it heals, but the clicking and popping often remain.
Q. If you have osteoarthritis, should you keep exercising?
A. Osteoarthritis is not a reason to stop moving. It’s a reason to get moving, or keep moving, so that overall health is maintained and the joint fluid can do its job to reduce friction and provide nutrition to the surface.
Often, we’re told to pay attention to pain and avoid it, so many people shut down. This approach can result in a devastating loss of motion, pain, less mobility, worsening strength, poor health because of the lack of mobility, and weight gain. Millions of people are in this situation, and general health decline is often associated with this approach.
