Manual therapy is a mainstay in physical therapy and rehab but there’s a lot we we don’t truly understand about its mechanism of action. We know it works; many studies show manual therapy has a positive influence on pain outcomes. But how manual therapy works has not been clearly elucidated. For those who have not critically investigated the details of manual therapy mechanisms will surely be quick to argue on behalf of biomechanical explanations. But these mechanical effects really have not been clearly demonstrated in literature. For example, did you know that it is really only possible to mobilize a joint in a direction completely perpendicular to the surface of the contact area on the skin. This is because the skin-fascia interface is frictionless as found in a 2002 study in the Journal of Clinical Biomechanics. This throws a wrench into the rationale of many thrust techniques that attempt to mobilize segments using variation in hand placement and force vectors.
I am not arguing that biomechanics absolutely do not matter in manual therapy. However, I do believe that a more promising mechanism is that the forces applied in manual therapy initiate a sequence of peripheral and central nervous system neurophysiologic changes which positively modulate the pain experience. Into this also plays the placebo effect, the effects of patient expectancy, and therapeutic alliance, all of which would contribute to the pain-relieving effects of manual therapy regardless of any mechanical explanation. I think as clinicians we need skepticism to mechanistic explanation of our interventions, especially when the rationale for these interventions contradict basic scientific evidence. We need to start considering how we educate patients and understand that if we use strict biomechanical explanations for our interventions we may perpetuate the patients’ perceptions of their bodies as fragile entities dependent on a clinician’s hands to “correct” their “misalignments.” While this is good for business, and some businesses depend on creating a sense of fragility in the minds of patients,this is not good for our patients. We should acknowledge that humans are innately resilient, adaptable, and capable of pain relief without being dependent on continual “correction” and “adjustments.”