Are hip and knee kinematics and training load characteristics relate to pain intensity and physical function level in runners with Patellofemoral Pain?

Background: Patellofemoral pain (PFP) is the most common running-related injury. Altered hip and knee kinematics and increases in weekly distance and running pace are often associated with PFP development and exacerbation. Research question: Are altered movements and training load characteristics (weekly distance and running pace) relate to pain intensity or physical function level in runners with PFP? Methods: Forty recreational runners with PFP (20 males and 20 females) participated in this cross-sectional observational study. Three-dimensional hip and knee kinematics were quantified during the stance phase of running. Weekly distance was defined as the average weekly kilometers of running and running pace as the average pace of the activity measured as minutes per kilometer. A visual analogue scale was used to evaluate worst knee pain during the last week. The anterior knee pain scale (AKPS) was used to evaluate knee functional score. A Pearson correlation matrix was used to investigate the association between each dependent variable (worst pain in the last week and AKPS score) and the independent variables (knee and hip kinematics, weekly distance and running pace). Results: There was no significantly correlation between kinematic variables, pain and functional score for both males and females separately and combined. Weekly distance (km/week) was found to positively correlate to pain intensity (r = 0.452; p < 0.05) in females with PFP. A simple linear regression revealed that weekly distance was significant predictor emerged of pain in females with PFP. Females exhibited significantly greater peak hip adduction and hip adduction ROM than the males and males had significantly greater running pace compared to females. Significance: Weekly distance should be considered in the clinical context during rehabilitation of PFP in females runners aiming at pain reduction.