FEATURE | Posted Oct. 10, 2016

Is knuckle cracking safe?

Cracks and pops not harmful, UC Davis study finds

While knuckle cracking may be irritating to others, Robert Boutin, a UC Davis professor of radiology and specialist in musculoskeletal imaging, wanted to know what exactly caused the cracking sound and whether it resulted in any harm.

“Twenty-five to 50 percent of people identify themselves as knuckle crackers at some point in their lives, Boutin said. “People come in all the time asking whether knuckle cracking is going to cause arthritis. But, they keep doing it because it gives them a feeling of relief from tension.”

Using real-time ultrasound, Boutin investigated what is heard and seen during a knuckle crack at the same time.

He found that the distinctive knuckle-cracking sound was caused by gas bubbles bursting into the synovial fluid in the joints, and physical examinations by hand-injury specialists found no problems in the joints of knuckle crackers.

“We have an intense interest in musculoskeletal imaging and caring for patients with orthopaedic issues, so we really wanted to know for our patients whether it was causing any problems.

"A larger study will help determine if there are longer-term hazards or benefits of joint cracking, but we’re excited we have found a way to answer some longstanding questions about the safety of this common habit,” he said.