Is Knuckle Cracking Safe? Answers from an Orthopedic Hand Surgeon

Hand surgeon Omar Nazir, MD answers your questions about knuckle cracking.

Crack!  Pop!  Snap!  We are all familiar with the unique sounds that come from our joints.  While knuckle cracking causes some to breathe a side of relief, other cringe at the sound.

What causes the “cracking” sound?

Numerous theories have been proposed as to the cause of these sounds.  Over the past hundred years ideas ranging from the realignment of tendons, small bands within the joints (plicas) and sudden tightening of the joint capsule have all been proposed.

While these other theories have garnered some support, the most widely accepted is the sound being secondary to intra articular gas bubbles.  Normally, a small amount of gas is present dissolved within the joint fluid.  As the joint is taken through a range of motion, the pressure within the joint is altered, allowing the gas bubbles to become larger, consolidate and eventually pop, leading to the characteristic sound.  Typically, joints cannot be immediately “re-cracked” as the air bubble takes about 20 minutes to dissolve back into the joint fluid before beginning the process again.

What happens after the joint is cracked?

Using ultrasound, studies have been done to see what is actually happening within the joint.   While there is only indirect evidence of a prior bubble, this has been consistently demonstrated on imaging.

There have also been scientific studies looking at the status of the joints after being cracked.  Increased range of motion has been seen in the metacarpal joints (knuckle joints) after cracking.  No differences have been seen in regards to grip strength or pain experienced before or after cracking.

While there was an increase in range of motion seen, this difference was quite small.  The relative increase in range of motion seen in pre- versus post-cracked knuckles measured about 5 degrees.

What about long-term consequences? Can this lead to arthritis?

The short answer to this question is likely no, but the actual answer is considerably more complicated.  There is no evidence that knuckle cracking causes arthritis or any other chronic joint problems.  That being said, most studies look only at short-term outcomes.  Given the variety of factors that are involved in the development of arthritis, the role played by knuckle cracking is likely minimal, if it exists at all.

So do I need to find a new hobby, or can I keep cracking away?

Given all of the information we currently have, as long as it does not hurt, cracking is not bad, but not necessarily beneficial either.  If you are looking for a reason to tell someone to stop, you may need to keep looking.

Dr. Omar Nazir is currently an Assistant Professor in the Department of Orthopaedic Surgery at Oregon Health and Science University.  As a faculty member of the only academic medical center in the state of Oregon, his practice involves a wide breadth of pathology and patients.   He is the co-director of the microsurgery training lab and a member of the teaching faculty of the hand fellowship.  He is also involved in the training of residents and medical students.   His research interests include cutting edge surgical techniques and cost analysis projects.  Content courtesy of ASSH at www.blog.handcare.org