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Table 5 Overview of selected demographic and clinical moderators

From: Better Knee, Better Me™: effectiveness of two scalable health care interventions supporting self-management for knee osteoarthritis – protocol for a randomized controlled trial

Selected moderator variablesJustification  
Expectation of treatment effectsBased on evidence that greater treatment expectations are associated with more favourable outcomes in people with osteoarthritis [77,78,79].
Hypothesis: Participants in the intervention groups who have greater treatment expectations will report greater improvement in primary outcomes than those who have lower treatment expectations (relative to control group).
SexBased on evidence that being male is associated with better outcomes in pain and physical function after supervised strengthening exercises [80] and evidence from a review that being female is associated with greater weight loss intentions [81].
Hypothesis: Participants in the intervention groups who are male will report greater improvement in primary outcomes than those who are female (relative to control). Participants in the Exercise plus weight management group who are female will report greater improvement in primary outcomes than those who are male (relative to Exercise group).
Pain self-efficacyBased on evidence that higher self-efficacy associated with better outcomes in pain and quality of life after supervised neuromuscular exercise [82], and greater improvements in pain after and internet-delivered exercise and education program [83].
Hypothesis: Participants in the intervention groups who have higher self-efficacy at baseline will report greater improvement in primary outcomes than those who have lower self-efficacy (relative to control group).
Body mass indexBased on evidence that obesity is associated with better outcomes in quality of life after supervised aquatic exercise [84] and evidence from a review that higher initial BMI is associated with greater weight loss [85].
Hypothesis: Participants in the intervention groups who have a higher BMI will report greater improvement in primary outcomes (relative to control) than those who have a lower BMI. Participants in the Exercise plus weight management group who have a higher BMI will report greater improvement in primary outcomes than those with a lower BMI (relative to Exercise group).
Employment situationBased on evidence that being employed associated with greater improvements in pain after an internet-delivered exercise and education program [83].
Hypothesis: Participants in the intervention groups who are employed will report greater improvement in primary outcomes than those who are not employed (relative to control group).
History of knee surgeryChosen based on theoretical plausibility that knee surgical experience could affect expectations of outcomes and motivation
Hypothesis: Participants in the intervention groups who have a history of knee surgery will report less improvement in primary outcomes than those without (relative to control group).
Self-efficacy for eating controlBased on evidence from a review that better control of over-eating and dietary restraint is associated with weight loss and maintenance [86, 87].
Hypothesis: Participants in the Exercise plus weight management group who have higher self-efficacy for eating control will report greater improvement in primary outcomes than those with lower self-efficacy for eating control (relative to Exercise group and to control group).
DepressionBased on evidence that fewer depressive symptoms is associated with better outcomes in pain and physical function after supervised strengthening exercises [80].
Hypothesis: Participants in the intervention groups who have more depressive symptoms at baseline will report less improvement in primary outcomes than those who have less depressive symptoms (relative to control group).