What Prognostic Indicators and Treatment Mechanisms Exist for Efficacious Treatments in People With Patellofemoral Pain? A Secondary Meta-Regression With an Updated Search

OBJECTIVE: To investigate the prognostic and mechanistic variables associated with efficacious treatments in people with patellofemoral pain (PFP). DESIGN: Updated intervention systematic review with de novo meta-regression. LITERATURE SEARCH: We searched MEDLINE, Web of Science, and Scopus from inception until October 2023 for randomised controlled trials (RCTs) involving people with PFP. STUDY SELECTION CRITERIA: High-quality RCTs (scoring ≥7 on the PEDro scale) involving participants with PFP and at least one treatment arm involving an efficacious intervention. DATA SYNTHESIS: We extracted homogenous pain and function data to calculate effect sizes to regress with baseline prognostic (e.g., symptom duration) and mechanistic (e.g., strength change) data. RESULTS: Thirty-four high-quality RCTs involving 1,526 people with PFP were included. For knee-targeted exercise, we identified symptom duration (R₂ = 0.68), older age (R₂ = 0.31), and low baseline knee extensor strength (R₂= 1.0) as significant prognostic variables. For hip-and-knee-targeted exercise, we identified older age (R₂= 0.37), greater mass (R₂= 0.28), and greater baseline hip abduction torque (R₂= 1.0) as significant prognostic variables. We also identified a significant mechanistic association between pain and increased knee extensor torque (R₂= 0.99). For hip-targeted exercise, we identified lower height as a significant prognostic variable (R₂= 0.96-0.99) and a significant mechanistic association between both pain and function and increased hip abduction (R₂= 0.93-0.96) and hip external rotation (R₂= 0.96-0.97) strength. CONCLUSIONS: Prolonged symptom duration, older age, and greater mass are prognostic variables for people with PFP. Increasing hip and knee muscle strength may be mechanisms underpinning positive responses to exercise therapy.