Synopsis Manual therapy interventions are popular among individual health care providers and their patients; however, systematic reviews do not strongly support their effectiveness. Small treatment effect sizes of manual therapy interventions may result from a "one-size-fits-all" approach to treatment. Mechanistic-based treatment approaches to manual therapy offer an intriguing alternative for identifying patients likely to respond to manual therapy. However, the current lack of knowledge of the mechanisms through which manual therapy interventions inhibit pain limits such an approach. The nature of manual therapy interventions further confounds such an approach, as the related mechanisms are likely a complex interaction of factors related to the patient, the provider, and the environment in which the intervention occurs. Therefore, a model to guide both study design and the interpretation of findings is necessary. We have previously proposed a model suggesting that the mechanical force from a manual therapy intervention results in systemic neurophysiological responses leading to pain inhibition. In this clinical commentary, we provide a narrative appraisal of the model and recommendations to advance the study of manual therapy mechanisms. J Orthop Sports Phys Ther 2018;48(1):8-18. doi:10.2519/jospt.2018.7476.

When a physical therapist provides a manual therapy (MT) intervention for a patient presenting with pain and the patient experiences a positive clinical outcome, we cannot answer as to why this occurs. Would we continue to devote valuable time and financial resources to learning and improving our skills in providing MT interventions if the related clinical outcomes were placebo responses? In this Viewpoint, the authors conceptualize placebo as an active and important mechanism of MT and argue that placebo mechanisms deserve consideration as an important component of the treatment effect. J Orthop Sports Phys Ther 2017;47(5):301-304. doi:10.2519/jospt.2017.0604.

BackgroundExpected pain relief from treatment is associated with positive clinical outcomes in patients with musculoskeletal pain. Less studied is the influence on outcomes related to the preference of patients and providers for a specific treatment.ObjectivesWe sought to determine how provider and patient preferences for a manual therapy intervention influenced outcomes in individuals with acutely induced low back pain (LBP).Participants and methodsPain-free participants were randomly assigned to one of two manual therapies (joint biased [JB] or constant touch [CT]) 48 hours after completing an exercise protocol to induce LBP. Expectations for pain relief and preferences for treatment were collected at baseline, prior to randomization. Pain relief was assessed using a 100 mm visual analog scale. All study procedures were conducted in a private testing laboratory at the University of Florida campus.ResultsSixty participants were included in this study. After controlling for preintervention pain intensity, the multivariate model included only preintervention pain (B=0.12, p=0.07) and provider preference (B=3.05, p<0.0001) and explained 35.8% of the variance in postintervention pain. When determining whether a participant met his or her expected pain relief, receiving an intervention from a provider with a strong preference for that intervention increased the odds of meeting a participant’s expected pain relief 68.3 times (p=0.013) compared to receiving any intervention from a provider with no preference. Receiving JB intervention from any provider increased the odds of meeting expected relief 29.7 times (p=0.023). The effect of a participant receiving an intervention they preferred was retained in the model but did not meet the criteria for a significant contribution.ConclusionOur primary findings were that participant and provider preferences for treatment positively influence pain outcomes in individuals with acutely induced LBP, and joint-biased interventions resulted in a greater chance of meeting participants’ expected outcomes. This is contrary to our hypothesis that the interaction of receiving an intervention for which a participant had a preference would result in the best outcome.

The purpose of this study was to compare the immediate change in temporal summation of heat pain (TSP) between spinal manipulation (SMT) and spinal mobilization (MOB) in healthy volunteers. Ninety-two volunteers (24 males; 23.8 ± 5.3 years) were randomized to receive SMT, MOB or no treatment (REST) for one session. Primary outcomes were changes in TSP, measured at the hand and foot, immediately following the session. A planned subgroup analysis investigated effects across empirically derived TSP clusters. Primary outcome: There were no differences in the immediate change in TSP measured at the foot between SMT and MOB, however both treatments were superior to the REST condition. Subgroup analysis: The response to a standard TSP protocol was best characterized by three clusters: 52% no change (n = 48, 52%); facilitatory response (n = 24, 26%), and inhibitory response (n = 20, 22%). There was a significant time by treatment group by cluster interaction for TSP measured at the foot. The inhibitory cluster showed the greatest attenuation of TSP following SMT and MOB when compared to REST. These data suggest lumbar manual therapies of different velocities produce a similar localized attenuation of TSP, compared to no treatment. Attenuation of localized pain facilitatory processes by manual therapies was greatest in pain-free individuals who demonstrate an inhibitory TSP response. Perspective The attenuation of pain facilitatory measures may serve an important underlying role in the therapeutic response to manual therapies. Identifying patients in pain who still have an inhibitory capacity (i.e. an inhibitory response subgroup) may be useful clinically in identifying the elusive “manual therapy” responder.

Background Context: Peripheral differences often do not adequately account for variation in reports of pain intensity in people with musculoskeletal pain.Purpose: Here we sought to determine the extent to which structural differences in the brain (grey matter density) of pain free individuals might relate to subsequent pain (or lack thereof) after standardized peripheral muscle injury (i.e. micro trauma from high intensity exercise). Study design: This was an observational laboratory-based study that was a secondary analysis from a larger trial.Methods: Participants completed baseline testing (functional MRI and quantitative pain testing) followed by high intensity trunk exercise to induce delayed onset muscle soreness in the erector spinae. Forty-eight hours later, back pain intensity ratings were collected and all participants were re-imaged. Grey matter density was determined using voxel-based morphometry. The 'asymptomatic' group (no reports of any pain within 48 hour after induction) to a 'pain' group (rating of pain at rest and movement pf >20 on a 101-point numeric rating scale).Results: Our results revealed several large clusters where, compared to participants with pain, asymptomatic participants had significant greater grey matter density. These brain regions included left medial frontal gyrus, left middle occipital gyrus, left middle temporal gyrus, left inferior frontal gyrus, and right superior frontal gyrus.