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Knuckle Cracking Good News

Researchers from the radiology department at University of California, Davis Health System have studied the phenomenon of knuckle cracking by simultaneously recording audio and ultrasound imaging from 17 women and 23 men. The group included 30 habitual knuckle crackers and 10 who were not.

Some individuals cracked their knuckles up to 20 times per day for the past 40 years.

Orthopedists blinded to the participants' knuckle-cracking history evaluated the participants for grip strength, range of motion and laxity of each MPJ both before and after the ultrasound examination.

Two radiologists interpreted the ultrasound images, and said, "What we saw was a bright flash on ultrasound, like a firework exploding in the joint," Dr. Boutin said. "It was quite an unexpected finding."

They believe the cracking sound and bright flash on ultrasound are related to the dynamic changes in pressure associated with a gas bubble in the joint.

No disability, pain or deformity was associated with knuckle cracking. 

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The author has no conflicts of interest to disclose related to this subject