Snap, Crackle, Pop! Things that go “pop” in the Night

PT Blog   •   November, 2018

“We do not fear the unknown. We fear what we think we know about the unknown.” – Unknown (pun intended!)

Stop me if you’ve seen this scene before: A remote campsite in the middle of the woods, friends sitting around a fire roasting marshmallows and telling ghost stories. Suddenly, during the middle of a harrowing tale about a camper from long ago who drowned in the nearby lake, you hear a rustling in the brush. One of your friends shines a light in the direction, but again… a noise… this time closer. Close enough to hear, but indistinguishable. A chill begins to overcome you; you don’t believe in ghosts but this night is just spooky enough to spark some self-doubt. Again, the noise, but this time it sounds almost like someone is drip-drying, each drop of water splashing lightly on the brush underneath. Drip…. DRIP….. DRIPPPP!!!! It’s getting louder, approaching quickly, and suddenly… IT APPEARS! But, instead of the ghost of dead camper, it’s just a dog from the nearby campsite looking for a midnight snack.

We all fear the unknown – or the misunderstood. And like most things in life, that fear is usually perception that is not grounded in fact. The physical therapy realm is not without its own culprit, and none may be more scrutinized or vilified than the frightening, petrifying, spine-chilling phenomenon known as… JOINT NOISES! This blog post will attempt to set the record straight on crepitus: what is it, why it occurs, and why it’s not as bad as it appears.

What it crepitus?
Crepitus is defined as “a clinical sign in medicine that is characterized by a peculiar crackling, crinkly, or grating feeling or sound under the skin, around the lungs, or in the joints.”Although several hypotheses exist as to the underlying pathoanatomical mechanism, the truth remains unknown. Research points toward two primary causes: 1) a sudden collapse of a cavitation bubble or 2) the formation of clear space or bubble.2 Regardless of the underlying cause, the point is the same: joint noises are a common occurrence of a healthy joint and rarely correlate with injury or disease. One recent study by Pazzinatto et al highlights this fact: they examined over 300 women (50% with patellofemoral pain, 50% without) and concluded that “knee crepitus had no relationship with function, physical activity level, worst pain, pain climbing stairs or pain squatting.”3 Other causes of physiological crepitus: snapping of ligaments over bony prominences, catching of synovium or plica, and hypermobile/discoid meniscus.4

How do I know if crepitus is pathologic?
Although the majority of joint crepitus is physiologic and not correlated with joint injury or disease, there are instances when joint noise may be problematic. Most notably, crepitus is considered pathologic only when it is accompanied by pain and/or swelling (extra-articular) or joint effusion (intra-articular). Causes of pathological crepitus include degenerative changes (i.e. knee osteoarthritis, patellofemoral arthritis), pathological plica, patellofemoral instability, pathological snapping knee syndrome, and postsurgical crepitus.

What should I do about it?
Ultimately, the treatment for crepitus depends on the origin. If pathologic, treatment directed at the underlying cause is pursued. For osteoarthritis: viscosupplementation, anti-inflammatory medications, or joint replacements are all viable options; for patellofemoral instability: bracing, quad / hip strengthening, or surgery could be potential treatments. Conversely, with physiological crepitus (the majority of joint noise observed and questioned by patients), care should be taken to properly assess and address anxiety and concerns promptly and intelligently. Lewis Wolpert in his book “Six Impossible Things Before Breakfast5 ” states that “it is action based on belief that ultimately matters,” thus amplifying the importance of sound explanation and education regarding joint noise to prevent fear-avoidance behaviors and pain catastrophizing.6

There are many things in life that appear threatening and dangerous on the surface, but once explored, are nothing more than perceptions of fear that we have fabricated and perpetuated causing self-imposed limitations or safeguards that can be detrimental to optimal daily living. So, don’t be afraid – all things that crack are not broken, and the unknown is usually not as frightening as it appears. In the words of the great Franklin D. Roosevelt, the “only thing we have to fear is fear itself.”

Contributing Author Credit: W. Evan Stringfellow, PT, DPT, CSCS, Cert. DN

Edited by: Ashley Theobald, DPT

Photo by: Charles Deluvio 🇵🇭🇨🇦 on Unsplash


  2. Kawchuk GN, Fryer J, Jaremko JL, Zeng H, Rowe L, Thompson R. Real-time visualization of joint cavitation. PLoS One. 2015;10(4):e0119470
  3. Pazzinatto MF, Priore LBD, Ferreira AS, Briani RV, Ferrari D, Bazett-Jones D, Azevedo FM. Knee crepitus is prevalent in women with patellofemoral pain, but is not related with function, physical activity and pain. Phys Ther Sport. 2018 Sep;33:7-11. doi: 10.1016/j.ptsp.2018.06.002. Epub 2018 Jun 6
  4. Song SJ, Park CH, Liang H, Kim SJ. Noise around the Knee. Clin Orthop Surg. 2018;10(1):1-8. doi:10.4055/cios.2018.10.1.1.
  5. Wolpert L. Six Impossible Things before Breakfast. The Evolutionary Origins of Belief. Chatham: Faber& Faber, 2007.
  6. Robertson CJ. Joint Crepitus – are we failing our patients? Physiother Res Int. 2010; (10): 185-188.

About the Author:

Ashley Theobald, D.P.T. – Ashley was born and raised in a small town in Alabama. She attended the University of South Alabama and was an advanced undergraduate student completing her Bachelor of Science degree in pre-professional health sciences in 2012. She then graduated with her doctorate in physical therapy in 2014. During her first year of PT school she met and married her husband, Ben. They moved to Nashville, TN where she worked for 3 years in an outpatient clinic full time and at Vanderbilt Stallworth Rehabilitation Hospital PRN. She is now working for ATI Physical Therapy full-time in Greenville, SC. She has been an avid health and fitness fan playing softball growing up, tennis in high school, and completing 2 half-marathons in college. She enjoys traveling overseas and has completed 2 short-term medical mission trips for physical therapy in the Dominican Republic (2013) and Haiti (2015), with intentions of returning yearly.
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