MD, PhD, MAE, FMedSci, FRSB, FRCP, FRCPEd.

This review was aimed at quantifying the proportion attributable to contextual effects of physical therapy interventions for musculoskeletal pain. Randomized placebo-controlled trials evaluating the effect of physical therapy interventions on musculoskeletal pain.

Risk of bias was evaluated using the Cochrane risk-of-bias tool for randomized trials (ROB 2.0). The proportion of physical therapy interventions effect that is explained by contextual effects was calculated, and a quantitative summary of the data from the studies was conducted using the random-effects inverse-variance model (Hartung-Knapp-Sidik-Jonkman method).

Sixty-eight studies were included in the systematic review (total number of participants: n=5,238), and 54 placebo-controlled trials informed our meta-analysis (participants: n=3,793). Physical therapy interventions included:

  • soft tissue techniques,
  • mobilization,
  • manipulation,
  • taping,
  • exercise therapy,
  • dry needling.

Placebo interventions included manual, non-manual interventions, or both.

The results show the following:

  • The type of treatment with the largest proportion not attributable to the specific effects (PCE) for pain intensity assessed immediately after the intervention was mobilization, which represented 87% of the overall treatment effect (PCE = 0.87, 95% CI: 0.54, 1.19).
  • For soft tissue techniques, the PCE was 81% of the overall treatment effect (PCE = 0.81, 95% CI: 0.64, 0.97).
  • For dry needling, the PCE was 75% (PCE = 0.75, 95% CI: 0.36, 1.15).
  • For manipulation techniques the PCE was 74% (PCE = 0.74, 95% CI: 0.33, 1.14).
  • For taping the PCE was 69% of the overall treatment effect (PCE = 0.69, 95% CI: 0.48, 0.89).
  • The smallest proportion not attributable to the specific intervention itself for pain intensity was exercise therapy accounting for 46% of the overall treatment effect (PCE = 0.46, 95% CI: 0.41, 0.52).

The authors concluded that the outcomes of physical therapy interventions for musculoskeletal pain were significantly influenced by contextual effects. Boosting contextual effects consciously to enhance therapeutic outcomes represents an ethical opportunity that could benefit patients.

This sounds as though most of the treatments in question rely mainly on placebo effects. But what about conventional therapies? The authors point out that the PCEs of general medicine and surgery in pain-related conditions are also large. In particular, the overall proportion not attributable to the specific effects of general medicine interventions is high (PCE = 65%), with higher values observed in semi-objective and objective outcomes (PCE = 78 and 94%, respectively) than in subjective outcomes (PCE = 50%).

What does that mean for healthcare routine?

As placebo and other context effects are unreliable, usually short-lived, and not normally affecting the cause of the problem (but merely the symptoms), I would say that those treatments with a very high PCE are of limited value, paticularly if they are also expensive or burdened with risks. Of the treatments studied here, I would – based on the current analysis – avoid the following therapies for pain management:

  • mobilization,
  • soft tissue techniques,
  • dry needling,
  • manipulation,
  • taping.

By and large, these are also the conclusions drawn from various other strands of evidence that we have repeatedly discussed in previous posts.

2 Responses to Which portion of a treatment effect is attributable to contextual effects?

  • Prof. Ernst, I was very interested in your blog about placebos, but was disappointed to see that you did not include the most popular placebo used in healthcare. Paracetamol.
    https://www.ox.ac.uk/research/what%E2%80%99s-point-paracetamol
    Did you omit discussing paracetamol on purpose, knowing the dangers of it, or was it an omission because you are so obsessed with criticism of some forms of care that you are blinded to reality?

    • amd I had thought that even the dumbest of my readers has by now understood that my blog focusses on so-called alternative medicine (SCAM)

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