Review Mechanisms of action of therapeutic exercise for knee and hip OA remain a black box phenomenon: an (IPD) mediation study..., 2023, Runhaar et al

[rvallee]

Mechanisms of action of therapeutic exercise for knee and hip OA remain a black box phenomenon: an individual patient data mediation study with the OA Trial Bank

https://rmdopen.bmj.com/content/9/3/e003220

Abstract

Objectives
To evaluate mediating factors for the effect of therapeutic exercise on pain and physical function in people with knee/hip osteoarthritis (OA).

Methods
For Subgrouping and TargetEd Exercise pRogrammes for knee and hip OsteoArthritis (STEER OA), individual participant data (IPD) were sought from all published randomised controlled trials (RCTs) comparing therapeutic exercise to non-exercise controls in people with knee/hip OA. Using the Counterfactual framework, the effect of the exercise intervention and the percentage mediated through each potential mediator (muscle strength, proprioception and range of motion (ROM)) for knee OA and muscle strength for hip OA were determined.

Results
Data from 12 of 31 RCTs of STEER OA (1407 participants) were available. Within the IPD data sets, there were generally statistically significant effects from therapeutic exercise for pain and physical function in comparison to non-exercise controls. Of all potential mediators, only the change in knee extension strength was statistically and significantly associated with the change in pain in knee OA (β −0.03 (95% CI −0.05 to −0.01), 2.3% mediated) and with physical function in knee OA (β −0.02 (95% CI −0.04 to −0.00), 2.0% mediated) and hip OA (β −0.03 (95% CI −0.07 to −0.00), no mediation).

Conclusions
This first IPD mediation analysis of this scale revealed that in people with knee OA, knee extension strength only mediated ±2% of the effect of therapeutic exercise on pain and physical function. ROM and proprioception did not mediate changes in outcomes, nor did knee extension strength in people with hip OA. As 98% of the effectiveness of therapeutic exercise compared with non-exercise controls remains unexplained, more needs to be done to understand the underlying mechanisms of actions.

 

[Utsikt]

The absence of a strong mediating effect through gains in knee extension muscle strength was indirectly supported by a recent and large RCT (N=377)40; after an 18-month strength training intervention programme for people with knee OA, there were no significant differences in pain and function between the high-intensity strength training group and the attention control group, despite significant differences in quadriceps strength gains between the groups.

Also a meta-regression analysis of RCTs concluded that therapeutic exercise would require considerably large gains in muscle strength (30%–40%) for only small benefits in OA symptoms, and, therefore, the authors deemed that a predominant focus on muscle strength as the mechanism through which to obtain improvements in pain and function from exercise therapy is likely ‘inappropriate in clinical practice’.41

So we’re going to stop using exercise as a treatment for OA now?

Our results are consistent with conclusions of previous studies; which all forms of therapeutic exercise, at least those tested in the IPD available for the current analyses, lead to similar effects on OA symptoms.11 41 Therefore, other important aspects of therapeutic exercise, such as patients’ preferences,50 adherence, patient–clinician therapeutic relationship51 and availability of resources, may need to be considered when deciding on therapeutic exercise for people with knee or hip OA.7 50 52

Apparently not. They’ll keep offering it, even when they know it won’t do anything. Because there’s no way that poor methodology could have created the illusion of a treatment effect.. /s

 

[Jonathan Edwards]

A useful analysis. I can now point out that not only is the claim that exercise works for OA likely due to bias but that even if it helps it doesn't do anything to strength and control (which are the explanations always given).

 

[Mij]

2026
Conclusion and relevance Evidence on exercise for osteoarthritis remains largely inconclusive, suggesting negligible or short-lasting small effects comparable to, or less effective than, other treatments. These findings question its universal promotion and highlight the need to revisit research priorities and clinical discussions around its worthwhileness.