How does manual therapy work? Historically we have been taught the biomechanical model of facet mobility with upglides and downglides and hypomobilities and syndromes and derangements and so on. These models are great for teaching and laying out a procedural flow and a clinical thought process. There are conflicting theories depending on which school of thought you subscribe to. However, it seems that a whole bunch of techniques seem to work especially when we are specific with our treatments. Interestingly, they work OK even when we aren’t so specific. I pose the question, can we really change collagen in one or two or even ten sessions of manual therapy interventions? If the answer is no, or even very minimal changes, then what really occurs to get such dramatic results?
With the development of functional MRI’s (fMRI) and neural mapping, it has become evident that there is specific cortical representation of each individual finger in the human brain. It is not too far of a leap to propose that there is cortical representation of each individual facet joint on this same map. It has been demonstrated that in experimental models with monkeys, that when their fingers are sewn together, there is a very quick change in the cortical map in which the two individual fingers are represented as one. This is quickly reversed if the procedure is reversed in a relatively short time frame.
Now put this into the reference of a stiff facet joint. Our brains, being inherently efficient, will likely stop recognizing two individual facets and now represent these as only one. If this is treated at an early phase, the nervous system may reset and continue to recognize these as two individual segments. Give this enough time, say greater than 30 days and this neuroplastic change starts to become further “burned in”. This now correlates very well with the chronic patient, who becomes more difficult to treat. This patient may now truly have a “mechanical” problem causing poor movement leading to further stress on the adjacent segments, poor neuro-muscular patterns, specific atrophy of the stabilizing muscles of that segment. The difficulty in treating this patient is that their cortical movement representation is now “smudged” and poorly represented. This is now a high functioning neurologic patient. Add to this the biopsychosocial components of chronic pain and you now have a complicated patient.
So back to the original question-how does manual therapy work? And which technique is the right one? We may not be too far off in treating via a biomechanical, tissue provocation model, however, we likely are not making the changes that we think at a local level. For example, if we think we are mobilizing a facet joint and it moves better with less pain, did the change occur at the joint itself, or did we stimulate the cortical representation of the individual facets? Was there a global neurologic response that occurred? Was there a reflexive facilitation of the muscles surrounding the joint.
Consider the evidence for improved multifidus and transverse abdominus firing following a joint manipulation.
o do we change how we teach clinical examination and treatment? Probably not. Do we change our explanations on how it works? We have to. As David Butler proposed, manual therapists are “brain reinhibitors and sculptors”.