MD, PhD, FMedSci, FRSB, FRCP, FRCPEd

Belgian researchers (if I remember correctly, I was the external examiner of the PhD of one of them) conducted a survey aimed at examining the beliefs about the cracking sounds often heard during high-velocity low-amplitude (HVLA) thrusts in individuals with and without personal experience of this technique.

The researchers included 100 individuals. Among them, 60 had no history of spinal manipulation, including 40 who were asymptomatic with or without a past history of spinal pain and 20 who had nonspecific spinal pain. The remaining 40 patients had a history of spinal manipulation; among them, 20 were asymptomatic and 20 had spinal pain. Participants attended a one-on-one interview during which they completed a questionnaire about their history of spinal manipulation and their beliefs regarding sounds heard during spinal manipulation.

Mean age was 43.5±15.4 years. The sounds were ascribed to vertebral repositioning by 49% of participants and to friction between two vertebras by 23% of participants; only 9% of participants correctly ascribed the sound to the release of gas. The sound was mistakenly considered to indicate successful spinal manipulation by 40% of participants. No differences in beliefs were found between the groups with and without a history of spinal manipulation.

The authors concluded that certain beliefs have documented adverse effects. This study showed a high prevalence of unfounded beliefs regarding spinal manipulation. These beliefs deserve greater attention from healthcare providers, particularly those who practice spinal manipulation.

So, what causes the sound often heard during spinal manipulation? This is how one chiropractor explains it: “In simple terms, the sound of cavitation means that the vertebrae are being gently and properly realigned. The sound of dissolved air bubbles in the fluid around the vertebrae releasing is what makes the pop.” And this is what another chiro states: “The actual pop is called a cavitation, and it’s the release of gas that makes the popping sound. The joints of the spine are called synovial joints (check out this simple and detailed description here) and they produce a fluid called synovial fluid. Synovial fluid lubricates the joint (for movement) and nourishes it. The byproducts formed in the production of synovial fluid are gasses – oxygen, nitrogen and CO2. When a joint is gapped, or opened up, the gas is released and you hear a distinctive popping sound. It’s very similar to the release of gas bubbles when you cork a champagne bottle, and equally pleasant in its after effects.” Finally NHS Choices tells us this: “During spinal manipulation, you may experience a popping sensation in your joints and hear a popping or cracking sound. It is thought this is caused by gas bubbles in the fluids that surround your joints – this is a normal part of spinal manipulation and other manual treatments.”

In reality the pop is much to do about nothing. If you pull hard on one of your fingers, chances are that you generate the same phenomenon and sound. As with your finger, the pop from the vertebral joints has no therapeutic value.

4 Responses to The cracking sound during spinal manipulation: much to do about nothing

  • Hang on!
    “The joints of the spine are called synovial joints.”

    Misleading – the main inter-vertebral joints are symphyses. All but fused. No ‘cavitation’ is possible.
    The zygaphophyseal joints (between articular processes) are very small, could not contain much gas, and I can find no research showing any sound ever emanates from such joints.
    (Can anyone ‘crack’ or pop the interphalangeal joints of their little fingers?)

    On the other hand I have observed a chiropractor using techniques well known to magicians (e.g. Paul Daniels ‘Electric Chairs’) – and when I do talks on ‘The Magic of Alternative Medicine’ (and promote my book – ‘The Real Secrets of Alternative Medicine’) – I use a palmed plastic cracker to make the noise of a joint being popped.
    The cartoon may have it right!

    Evidence of joint cavitation from zygapophyseal joints please.
    Otherwise, patients should have a chaperone (preferably a magician) with them when they have a chiropractic manipulation, and if there is a sound, check out what is in the chiropractor’s hands!
    Watch out for sleights!

  • I’m a man of science but I love the pops:)

  • Much the same applies to the vigorous shoulder massage after a Turkish or Greek haircut/shave, which I have occasionally., and shall again soon.Very theatrical, but on what medical basis- none, I expect. Although I believe that very few of them have the nerve to give themselves fancy titles in order to fool gullible people. They just call themselves ‘barbers’.

  • If pops signify successful manipulation to patients, what does successful spinal manipulation, in physical terms, mean to them?

    Apart from the pops and twisting and stretching and massage and whatever else the therapist does, what do patients think a successful physical outcome of it all, precisely is supposed to be?

    Do they believe that their spines are being put back into the correct shape? The truth is that it is not the spine, specifically, which is being manipulated, it’s the upper body. It’s passive exercise for the upper body with exertion by proxy and pops thrown in for free.

    The authors of this study say that patients’ beliefs deserve greater attention. Patients deserve more than that. Patients should be given clear information about what manipulation of the spine specifically and precisely is supposed to achieve, in physical terms, if “spinal manipulation” is what patients understand themselves to be receiving.

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