Spinal Manipulation: What Is the Role of the “Pop” in Pain Relief?

Few sounds are as satisfying for patients and therapists alike as that of a profound “crack” during the delivery of spinal manipulation.  So satisfying in fact that providers rarely doubt this sound is indicative of a successful physical therapy treatment.  Thus, It may come as a surprise to many physical therapists that the evidence is not nearly so clear on the topic.  Let us review a recent publication and then offer our thoughts around the controversial topic of audible pops during spinal manipulation.

What does research show about audible spinal manipulation?

“Impact of audible pops associated with spinal manipulation on perceived pain: A systematic review” was published in 2022 and being a systematic review, it is the highest quality evidence available to date on this topic (Moorman).  The paper directly states “The main findings of this systematic review suggest moderate evidence that audible pops generated during the application of SMT are not likely to possess independent therapeutic benefit in their impact on pain outcomes”. Admittedly that is a direct hit to our bias surrounding spinal manipulation, but before we surrender the case closed let’s take a deeper look at the findings.

While there were a good number of articles identified, only five papers ultimately met all inclusion criteria and were included for review.  This is a fairly limited sample of papers and patients to form a strong conclusion upon.  Perhaps even more importantly, contextual factors were not considered in any of the reviewed publications. In other words, the meaning of the audible pop to the patient was not evaluated and analyzed alongside the respective outcomes.  This is key because as providers our ultimate goal is not to make broad brushed conclusions on whether or not something works, but instead to understand which variables are likely important to maximize outcome in each individual patient.

Currently the research is conflicted on what percentage of patients believe the audible pop is important, with a 2017 article suggesting fewer than half and a more recent paper suggesting a much higher percentage harbor believing this is the case (Bergamino, Demoulin).  Anecdotally, few physical therapists will deny the prevalence of patients directly stating “I feel if my neck (or back) would crack it would really help”.  Considering what is now known about the strong role of expectation in clinical outcomes, this information must be gathered to deduce the expected role of audible popping for a given patient presenting for treatment.

Our Current Thoughts on Spinal Manipulation and the Role of “Popping”

Ultimately this review paper, while not without the faults discussed above, serves to challenge our bias that audible pops are always necessary for best outcomes.  Our current stance is as follows:

• Audible pops are not absolutely necessary for patient improvement during spinal manipulation. The review paper discussed here should broaden the therapists thinking to appreciate outcomes can be gained through manual therapy in the absence of popping sounds
• Patient expectation is often a primary driver of outcomes, always gather this information and treat accordingly. Being able to create audible pops when the patient believes such sounds indicate successful treatment will likely enhance your results
• Increasing the speed of your spinal manipulation delivery will likely result in more audible popping (Williams). When your desired neurophysiological outcome depends on rate of force delivery, audible pops can serve as excellent feedback in your skill refinement

While the important role of spinal manipulation in the treatment of back and neck pain has been consistent for many years, the explanation of how and why these techniques deliver their benefit has been constantly evolving.  If you are interested in learning the knowledge and skill to effectively incorporate spinal manipulation into your physical therapy practice, check out our Total Spine Thrust Manipulation weekend seminar.  This two day course dives deep into all areas of research and psychomotor refinement arming you with the who, when, and how to maximize your clinical outcomes.

References

Bergamino M, Vongher A, Mourad F, Dunning J, Rossettini G, Palladino M, Fernández-de-Las-Peñas C, Testa M, Maselli F. Patient Concerns and Beliefs Related to Audible Popping Sound and the Effectiveness of Manipulation: Findings From an Online Survey. J Manipulative Physiol Ther. 2022

Demoulin, Christophe, Damien Baeri, Geoffrey Toussaint, Barbara Cagnie, Axel Beernaert, Jean-François Kaux, and Marc Vanderthommen. 2018. “Beliefs in the Population about Cracking Sounds Produced during Spinal Manipulation.” Joint, Bone, Spine: Revue Du Rhumatisme 85 (2): 239–42.

Moorman, Annelieke Cesanne, and David Newell. 2022. “Impact of Audible Pops Associated with Spinal Manipulation on Perceived Pain: A Systematic Review.” Chiropractic & Manual Therapies 30 (1): 42.

Williams JM, Cuesta-Vargas A. Quantification of prone thoracic manipulation using inertial sensor-derived accelerations. J Manipulative Physiol Ther. 2014 May;37(4):230-5. doi: 10.1016/j.jmpt.2014.02.002. Epub 2014 Mar 20. PMID: 24656868.