What’s Really Happening When Your Spine “Pops” and "cracks" During an Adjustment?

At our Wanaka chiropractic clinic, one of the most common questions we hear is, “What was that pop?”

If you’ve ever had a chiropractic adjustment, you’ve probably noticed a “pop” or “crack” coming from your back or neck. It can sound dramatic — but it’s actually a very normal and well-studied phenomenon called joint cavitation. Understanding what this spine pop and crack is and how it relates to pain relief and joint function helps demystify what many people think is mysterious or even scary.

1. The Anatomy of a Spinal Joint

Spinal joints — especially the small ones between vertebrae called facet joints — are synovial joints. That means:

• They’re surrounded by a capsule of connective tissue.

• Inside is synovial fluid, a lubricating substance that helps the joint move smoothly.

• Dissolved in this fluid are tiny amounts of gases like nitrogen and carbon dioxide.

  
  

2. What Is Cavitation - the Spine pop and crack noise?

When a chiropractor performs a high-velocity, low-amplitude (HVLA) adjustment — a quick, targeted thrust — something interesting happens.

Here’s the sequence in simple terms:

1. Rapid separation: The two joint surfaces are gently but quickly pulled apart.

2. Pressure drop: This increases the space and decreases pressure inside the joint capsule.

3. Gas bubble formation: Dissolved gases come out of solution and form tiny bubbles.

4. Audible pop: As these bubbles rapidly form and collapse, they generate the familiar “pop” sound. https://rdcu.be/e3xGa

This process — driven by fast pressure changes — is called cavitation. Importantly, the sound is not bones grinding or snapping; it’s gas coming out of the joint fluid.

3. Does the Pop Mean Success?

Many people assume the pop means the joint has been “fixed.” But clinical studies suggest the relationship isn’t that simple:

• Research shows joint motion and pain relief can occur even without an audible pop. The therapeutic benefit doesn’t rely on sound alone.(1)

• A 2003 study in Archives of Physical Medicine and Rehabilitation found no difference in pain or motion improvement between spinal manipulations that produced a pop and those that did not. (2)

In other words, the presence or absence of a pop doesn’t reliably predict the outcome.

4. What Happens to the Joint Itself?

During the cavitation moment:

• The joint surfaces gap slightly, which can temporarily change the mechanics around the joint.

• This gapping may allow adhesions or restrictions to release, and can immediately increase range of motion. https://rdcu.be/e3xGa

• Imaging studies — including real-time MRI of finger joints — have visually confirmed this separation and bubble formation. (4)

These mechanical changes are thought to help the joint move more freely afterward.

5. How This Affects Pain and Function

So, you might wonder: how does this all help someone feel better?

Several research-based mechanisms may explain this:

a. Improved Joint Mobility

When a joint has become stiff from injury, postural strain, or everyday wear-and-tear, its range of motion narrows. Chiropractic adjustments help restore movement, which:

• Reduces stiffness.

• Enhances signals from motion receptors that can inhibit pain according to pain-modulation theories. (3)

b. Neuromuscular and Reflex Effects

Some studies suggest that when a joint cavitates, it may alter muscle reflex activity:

• Certain reflex pathways — like muscle spindle stretch reflexes — can decrease after an adjustment with cavitation.

• This input change might help reduce muscle guarding, a common source of pain and tension. https://rdcu.be/e3xGa

Although more research is needed, these kinds of neurological responses help explain why patients often feel immediate relief.

c. Pain Signal Modulation

Beyond mechanics, spinal manipulation appears to influence how the nervous system processes pain — possibly by changing sensory input around the joint and interrupting pain feedback loops. https://rdcu.be/e3xGa

6. So What’s the Take-Home Message?

• The pop you hear is a natural gas bubble release — a side effect of the manipulation, not the therapeutic goal itself.

• You can get pain relief and improved function with or without a pop. Sound isn’t a reliable sign of effectiveness.(2)

• Cavitation may help by increasing mobility and influencing nerves and muscles around the joint — all of which contribute to reduced pain and improved joint function. https://rdcu.be/e3xGa

  
  

By understanding the mechanics behind spinal joint cavitation our goal is to inform clients about what occurs during an appointment. Helping patients feel more comfortable during chiropractic care, and focus on the resulting improvements in movement, pain reduction, and overall spinal health — not just the clap, pop, or crack.

If you’re experiencing back or neck discomfort in Wanaka and would like a professional assessment, our chiropractic team is here to help. Book an appointment today to discuss whether spinal manipulation is appropriate for you.

1. LaPelusa A, Bordoni B. High-Velocity Low-Amplitude Manipulation Techniques. [Updated 2023 Jun 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK574527/?utm_source=chatgpt.com

2. Timothy W. Flynn, PT, PhD., et al. The Audible Pop is Not Necessary for Successful Spinal High-Velocity Thrust Manipulation in Individuals with Low Back Pain. In Archives of Physical Medicine and Rehabilitation. July 2003. Vol. 84. No. 7. Pp. 1057-1060.

3.  https://chiro-trust.org/advanced/chiropractic-neck-pain/

4. Kawchuk GN, Fryer J, Jaremko JL, Zeng H, Rowe L, Thompson R. Real-time visualization of joint cavitation. PLoS One. 2015 Apr 15;10(4):e0119470. doi: 10.1371/journal.pone.0119470. PMID: 25875374; PMCID: PMC4398549.