Physical Activity Variability In Patellofemoral Pain And Its Relation To Clinical And Psychological Outcomes

Patellofemoral pain (PFP) often presents pain, disability, and psychological barriers during daily activities, reducing overall physical activity (PA). However, there is a lack of evidence on how PFP affects PA variability and its relation to clinical and psychological outcomes in PFP cohorts. PURPOSE: To compare PA variability between people with PFP and pain-free controls and evaluate its relation to pain severity, symptom duration, disability, and pain catastrophizing in people with PFP. METHODS: Thirty-four people with PFP (27 women, age: 24 ± 4 y, height: 168 ± 8 cm, mass: 66 ± 14 kg) and 34 pain-free controls (27 women, age: 23 ± 4 y, height: 165 ± 8 cm, mass: 64 ± 16 kg) completed the study. Participants wore a triaxial accelerometer over consecutive 7 days. We calculated variability (coefficient of variation) in daily steps and moderate-to-vigorous PA (MVPA). We assessed pain severity (numeric pain rating scale), symptom duration (months), disability (Knee Injury and Osteoarthritis Outcome Score-Patellofemoral subscale), and pain catastrophizing (Pain Catastrophizing Scale). Independent t tests or Mann-Whitney U tests evaluated group differences in PA variability. Spearman ρ correlation coefficients calculated the relation of PA variability with pain severity, symptom duration, disability, and pain catastrophizing. Correlation coefficients were interpreted as weak (<0.40), moderate (0.40-0.70), and strong (>0.70). Statistical analyses were performed using SPSS (version 28.0). Alpha was set a priori at p < 0.05. RESULTS: Age, height, and mass did not differ between groups (p > 0.05). People with PFP showed greater variability in daily steps (p < 0.001) and MVPA (p = 0.001) than pain-free controls. In people with PFP, greater variability in daily steps was moderately related to higher pain severity (ρ = 0.41; p = 0.016), while greater variability in MVPA was weakly related to higher pain severity (ρ = 0.36; p = 0.037). CONCLUSIONS: People with PFP demonstrated greater PA variability than pain-free controls, which positively related to more severe pain. Implementing strategies to minimize PA variability could be important in reducing pain in PFP cohorts. Future PFP research should explore the underlying factors contributing to increased PA variability and their potential implications for pain management.