Psychological factors associated with trial participation among patients eligible for total knee arthroplasty with a non-surgical treatment arm: a comparative cross-sectional study.

BACKGROUND AND PURPOSE: Knowledge of psychological factors' influence on patients' decisions to participate in randomized controlled trials (RCTs) is scarce. We aimed to compare levels of psychological factors in patients with knee osteoarthritis (OA) eligible for total knee arthroplasty in those who agree to participate in an RCT with those who declined.

METHODS

We compared anxiety and depression (Hospital Anxiety and Depression Scale [HADS]), pain-related fear of movement (Fear-Avoidance Belief Questionnaire [FABQ]), catastrophizing (Pain Catastrophizing Scale [PCS]), knee symptoms (Knee Osteoarthritis and Outcome Scale [KOOS]), and knee awareness (Forgotten Joint Score [FJS]), in patients in the Multidisciplinary Intervention in Total Knee Arthroplasty (MultiKnee) trial (n = 280) and in patients who declined (n = 373). Simple and multiple logistic regression models explored associations between psychological factors and patients' willingness to participate.

RESULTS

Patients declining participation had more fear avoidance (FABQ 1.6 points higher, 95% confidence interval [CI] 0.6-2.6), more knee awareness (FJS 4.0 points lower, CI 1.9-6.1), and worse KOOS scores (ranging from 3.4, CI 0.6-6.1 to 5.6 points, CI 3.1-8.2). In simple regression analysis, each 1-point increase in FABQ-Physical activity score was associated with a 3.9% decrease in odds of participating (OR 0.96, CI 0.94-0.99), and in adjusted analyses, a 3.0% decrease in odds (OR 0.97, CI 0.94-1.0). When considering a clinically meaningful difference of 4 points, this corresponds to a 14.7% reduction in crude odds and a 11.5% reduction in adjusted odds of study participation. Each 1-point increase in HADS Anxiety score was associated with a 5.4% increase in odds of participating (OR 1.05, CI 1.00-1.11). HADS Depression and PCS were not associated with RCT participation.

CONCLUSION

Patients with higher fear avoidance of physical activity were less willing to participate in the RCT, while patients with higher anxiety were more willing. These findings may weaken the generalizability of the findings from the RCT.