Influence of unilateral versus bilateral patellofemoral pain on physical activity, pain self-efficacy, and disability

Background: Patellofemoral pain (PFP) affects physical and psychosocial health; however, it is unclear if unilateral and bilateral PFP induce similar levels of impairments. Objectives: We aimed to compare physical activity (PA), pain self-efficacy, and disability between individuals with unilateral and bilateral PFP, and to compare these groups against pain-free controls. Design: Cross-sectional case-control. Method: Sixty-two individuals with PFP (25 unilateral and 37 bilateral) and 20 pain-free controls completed the PA assessment using an accelerometer by daily steps, light PA, and moderate-to-vigorous PA (MVPA). We also calculated variability in each PA variable. Pain self-efficacy and disability were measured using the Pain Self-Efficacy Questionnaire and Anterior Knee Pain Scale, respectively. Results: Individuals with bilateral PFP took fewer daily steps compared to pain-free controls (9568.1 +/- 3827.0 vs. 12,285.8 +/- 2821.2 steps/day; P = 0.018, Cohen d = 0.79), whereas individuals with unilateral PFP did not (11,099.2 +/- 3547.1 steps/day; P = 0.503, Cohen d = 0.37). Individuals with bilateral PFP showed greater variability in MVPA compared to individuals with unilateral PFP (42.9 +/- 23.1 vs. 29.0 +/- 15.9; P = 0.011, Cohen d = 0.91) and pain-free controls (42.9 +/- 23.1 vs. 17.6 +/- 6.1; P < 0.001, Cohen d = 1.21). Individuals with unilateral and bilateral PFP similarly exhibited less time spent in MVPA, greater variability in daily steps, lower pain self-efficacy, and greater disability compared to pain-free controls (P < 0.001, Cohen d = 1.14-3.89). Conclusions: Versus pain-free controls, individuals with bilateral PFP displayed greater variability in MVPA than individuals with unilateral PFP. However, it is important to note that unilateral PFP influenced time spent in MVPA, variability in daily steps, pain self-efficacy, and disability at similar levels to bilateral PFP.