Individuals with patellofemoral pain have impaired self-reported and performance-based function: Systematic review with meta-analysis and meta-regression

To determine impairments on self-reported/performance-based function in individuals with patellofemoral pain (PFP) as well as physical and non-physical factors potentially related with these impairments. We searched MEDLINE, Embase, CINAHL, Web of Science, and SPORTDiscus databases from inception until January 2024. We included studies comparing self-reported/performance-based measures of function between individuals with PFP and their pain-free limbs or pain-free individuals. Two independent researchers extracted the key information from each study. We performed meta-analyses for each self-reported/performance-based measure of function and meta-regressions to identify factors that might explain meta-analyses outcomes. We assessed the certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). We included 83 studies (2807 individuals with PFP and 2518 pain-free individuals). We identified very low to high certainty evidence that individuals with PFP have reduced self-reported (large effect sizes, standardized mean difference [SMD], -1.99; 95% confidence interval [CI]:-2.41,-1.57 to SMD, -4.87; 95% CI:-6.97,-2.77) and performance-based (small to large effect sizes: SMD, -.30; 95% CI:-.58, -.02 to SMD, -1.21; 95% CI:-2.71, -.29) measures of function compared to pain-free individuals, but there are no differences between limbs in individuals with unilateral PFP for the most of performance-based measures of function (small to moderate effect sizes, SMD, -.20; 95% CI:-.68, .27 to SMD, -.49; 95% CI:-1.02, .03). Age, body mass index, duration of symptoms and self-reported pain did not significantly explain self-reported function, whereas age did not significantly explain performance-based function (R2 25