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Spinal Manipulation- what's the crack?

Updated: Mar 9, 2021

From my years out in practice, I have seen the benefits of spinal manipulation (particularly when added to soft tissue techniques, home exercises and other lifestyle advice). Some patients have instant responses to manipulation alone, in terms of decreased pain, increased range of motion and/or improved muscle function. Others need other treatment techniques or advice (for example, regarding nutrition or stress) alongside/instead to aid their recovery. As I've said before, everyone is different so I never like to adopt a 'one size fits all' approach to patient management.

But seeing as spinal manipulation is such a large part of what Chiropractors (and Osteopaths) do, I thought I'd explore the theory behind how it works and current evidence...

History of Chiropractic

Specific spinal manipulations within Chiropractic first began with a guy called Daniel David Palmer in 1895. His theory was that a 'subluxation' (partial dislocation) of a joint within the spine could interfere with the nervous system and negatively influence health.

What is it that we actually do when we manipulate a joint?

The subluxation theory is still adopted by many chiropractors, although there is now less emphasis on just a 'bone out of place' approach and more of an emphasis on joint 'restriction' being down to small muscular imbalances either side of the spinal joint (without the joint being massively 'subluxed'/out of place as such). Personally I find that linking palpation findings with other assessments such as functional muscle testing, movement screening and muscle palpation allows for the best analysis of where in the spine to manipulate.

There are three types of movement that occur in each joint: active movement, passive movement and 'joint play'. When we palpate joints we usually feel for joint play.

When we feel joint play is restricted we can either mobilise the joint (grades 1-4 depending on range taken into) or do a manipulation (grade 5).

Manipulations are also known as 'adjustments' in Chiropractic. Adjustments are aimed at being as specific as possible, with regard to the joint and direction. They consist of a high velocity, low amplitude thrust.

Joint restrictions or dysfunction may be found both local to the site of the pain or further away. For example, research and guidelines have shown that adjusting the thoracic spine can help neck pain. This may be seen in a mechanical sense, in terms of hyper/hypomobile tissue compensations due to actual tissue shortening/lengthening, but also in a neurological sense by affecting the whole 'afferent input pool' and how the brain processes information.

(It's like the concept of whether a muscle is actually 'short', due to injury and actually less muscle fibers, or whether it's 'tight' neurologically, due to poor nervous system control!)

Let's explore these concepts behind manipulation/adjustments...


Mechanically, when we manipulate a joint we take it just past the elastic barrier of resistance into what's called the 'paraphysiologic space' (see diagram below), as a quick small thrust. This is associated with a 'gapping' of the joint and sometimes an audible 'pop/click' (although it doesn't always have to make this sound). The pop is basically the release of gas bubbles from the joint as the joint (synovial) fluid moves.

We therefore provide a stretch to the joint capsule, and help improve range of motion in joints and their surrounding tissue e.g. ligaments, muscles and tendons.

How long this mechanical change lasts is debated, so it's key to also look at other effects of manipulation alongside this.


Neurologically by manipulating the spine or other joints of the body, we attempt to improve input to the spinal cord and brain (Central Nervous System), thereby also improving output.

The thought is that we stimulate the Stretch Reflex, firing up muscle spindles aka 'proprioceptors' and other 'mechanoreceptors' in the small muscles either side of the spine (shown by EMG studies). Stimulation of these receptors feeds into the afferent input to the central nervous system. It's thought that this downregulates pain receptors (nociceptors) in terms of the Pain Gate Theory (large mechanical fibres close the pain gait, small pain fibres open it).

Dr Hedi Haavik states that faster adjustments may induce a a unique physiological change compared to slow stretch (adjustments as quick as under 200 milliseconds were shown to be needed to induce this!).

With better input (e.g joint position sense, also know as proprioception) to the nervous system, we improve the spinal cord and brain's ability to perceive what is happening in our surroundings and make accurate decisions about what subsequent output we should perform (e.g. muscle activation). It is all to do with what's called sensorimotor integration (integrating what we sense with our subsequent movements).

Without restoring proper nervous system function, it is thought that exercise/rehab may be less effective (if certain muscles aren't being 'switched on'/'activated'). Studies have shown the effects of manipulation on core muscle activation, necessary for postural control and all other movements. The brain basically uses the spine as an indicator of core body position, which is needed before moving any of the limbs. Research has shown abnormal recruitment of muscles in those with lower back pain, knee pain and idiopathic neck pain. Manipulation aims to increase facilitation of the deeper, more stabilizing muscles and inhibit the more superficial muscles that may be causing pain due to increased guarding of the joint or segments involved.

According to research, quoted by Dr Heidi Haavik, adjustments can change: reaction time, muscle reflexes, speed of information processing in the brain, joint position sense (proprioception), muscle strength in the legs, forearm muscle tone (with neck manipulation) and visual acuity.

How well these changes stay depends on the concept of neuroplasticity, where regular repeated actions can change the wiring of the pathways in the brain. More research is needed into how regularly input needs to be given to achieve changes in the central nervous system. This concept is very relevant to chronic pain, where the brain pathways are likely more hard wired than in one acute episode.

Again coming back to the anti 'one size fits all' approach, neuroplasticity and nervous system effects may be achieved in different ways, through adjustments, mobilizations or specific repeated home exercises, so it's finding what works best for each patient. As chiropractors, we believe manipulation has a potentially larger influence on the nervous system (secondary to the speed and subsequent stretch reflex, as described above) but this is not to say we can't use other techniques depending on the individual.

Overall concepts around Chiropractic treatment/adjustments:

  • Pain is also often the last thing to appear, dysfunction comes earlier.

  • It is often a case of 'the straw that broke the camels back'. Repetitive trauma and underlying dysfunction can add up, sometimes without us realizing it (until in some people, a tiny movement they usually do causes a painful episode).

  • The three stages of joint degeneration include: Dysfunction, Instability, Stabilization (degenerative changes like extra bone growth). The idea is to catch it at an earlier stage!

  • Adjustments/manipulation mainly aims to improve: Pain, range of motion, muscle function. Sometimes this is immediate, sometimes it takes repetition of the adjustment a few times.

  • This is one piece of the puzzle in a Biopsychosocial approach to managing pain! Pain can depend on other factors other than joint/muscle dysfunction. See my Blog post on 'Explaining Pain'. Often we use manipulation and hands on treatment alongside home exercises and lifestyle advice.

Evidence for manipulation...

1) The UK Evidence Report, 2010- stated that 'Spinal manipulation/mobilization is effective in adults for: acute, subacute, and chronic low back pain; migraine and cervicogenic headache; cervicogenic dizziness. Manipulation/mobilization is effective for several extremity joint conditions (such as pain related to hip and knee osteoarthritis) and thoracic manipulation/mobilization is effective for acute/subacute neck pain.'

2) NICE Guidelines, 2016- For lower back pain with/without sciatica: 'Consider manual therapy (spinal manipulation, mobilisation or soft tissue techniques such as massage) for managing low back pain with or without sciatica, but only as part of a treatment package including exercise, with or without psychological therapy.

3) Review of Manual Therapy Evidence, RCC, 2011- In addition to confirming the findings of the UK evidence report, ratings changed in a positive direction from inconclusive to moderate (positive) evidence ratings in three cases: manipulation/mobilisation [with exercise] for rotator cuff disorder. New moderate (positive) evidence was identified for soft tissue shoulder disorders not reported in the UK evidence report.

3) 'The Reality Check' by Dr Heidi Haavik, Director of Research at New Zealand College of Chiropractic. Study references included in book.

4) Article with collated studies on mechanical/neurological effects-

In conclusion, the evidence for manual therapy techniques, including spinal manipulation, is ever changing and exciting in terms of the neurophysiological responses of our bodies! Spinal/extremity joint manipulation, mobilisation, soft tissue therapies, home exercises and lifestyle advice are all options in terms of managing pain and improving function. Find a professional who works for you as an individual... Adaptability is key!

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