Can we predict which patients with patellofemoral pain are more likely to benefit from exercise therapy? A secondary exploratory analysis of a randomized controlled trial.

STUDY DESIGN: Secondary exploratory analysis of a randomized controlled trial comparing supervised exercise therapy to usual care in patients with patellofemoral pain (PFP).

OBJECTIVE: To explore which patients with PFP are more likely to benefit from exercise therapy.

BACKGROUND: Patellofemoral pain is a common condition for which exercise therapy is effective in reducing pain and improving function. However, not all patients benefit from exercise therapy.

METHODS: The present study explored patient characteristics that might interact with treatment effects of PFP in 131 patients treated with usual care or exercise therapy. These characteristics were tested for interaction with treatment in a regression analysis. The primary outcomes were function and pain on activity at a 3-month follow-up.

RESULTS: None of the tested variables had a significant interaction with treatment. A positive trend was seen for females with PFP: they were more likely to report higher function scores with exercise therapy than with usual care compared to males with PFP (β = 12.1; 95% confidence interval: 0.23, 24.0; P = .05). A positive trend was seen for patients with a longer duration of complaints (greater than 6 months); they were more likely to report higher function scores and to have less pain on activity with exercise therapy than with usual care compared to those with a shorter duration of complaints (β = 12.3; 95% confidence interval: -0.08, 24.7; P = .05 and β = -1.74; 95% confidence interval: -3.90, 0.43; P = .12, respectively).

CONCLUSION: Two factors, sex and duration of complaints, may have a predictive value for response to exercise therapy at 3-month follow-up. Due to the exploratory design of the study, future research should confirm this tendency.