The mechanisms that cause joints to crack or grind can differ from person to person. There are three primary theories about why facet joints crack, pop, or grind:
Cavitation. Surrounding each facet joint is a capsule of liquid, called synovial fluid, that lubricates the joints and allows for smooth, comfortable movements. One theory on crepitus suggests that air pressure within the joint is suddenly altered when the joint is cracked, resulting in the formation or collapse of an air cavity in the synovial fluid that produces a popping sound.1
Ligament or tendon snapping. When a tight or tense ligament is pulled across a surface of bone, cartilage, or another tendon or ligament, it can create a snapping noise similar to a joint crack or pop.
Bone grinding. Deteriorated cartilage surrounding a spinal joint can cause popping, cracking, or grinding. Cartilage may wear down from overuse and/or age, causing the bones of the joint to rub together and produce a grinding sensation and a sound similar to a crack or pop.
Dr. Brandon Buttry
Vishal K. Verma, DC, CCSP
Dr. Jonathan Donath, DC, MS