BACKGROUND & OBJECTIVE
Patellofemoral pain (PFP) is the most commonly reported running-related injury. Elevated patellofemoral joint stress is thought to play an important role in the cause of PFP. It remains unclear whether persons with PFP exhibit elevated patellofemoral joint stress during running. Tibiofemoral joint kinematics and kinetics are potential determinants of patellofemoral joint stress. However, it remains unknown which kinematic and/or kinetic variables are predictive of patellofemoral joint stress during running. The first purpose of the study was to determine whether recreational runners with PFP exhibit greater peak patella cartilage stress compared to pain-free individuals. The second purpose was to determine the kinematic and/or kinetic predictors of peak patella cartilage stress during running.
Twenty-two female recreational runners participated in the study (12 with PFP (mean 27.6 years) and 10 pain-free controls (mean 27.4 years)). All participants had to run at least 16 km/week. The duration of the PFP symptoms was 43.1±45.6 months in the PFP group.
Biomechanical evaluation of overground running trials at 2.7m/s were performed in a biomechanical laboratory. Kinematic outcomes of interest included peak knee flexion, as well as knee rotations in the frontal and transversal planes at the time of knee flexion. The knee extensor moment was the kinetic variable of interest. Magnetic resonance (MR) assessment was done to evaluate cartilage morphology and bone geometry of the knee and patellofemoral joint. Patella cartilage stress profiles were quantified using subject-specific finite element models. The biomechanical outcomes of interest were compared between groups. In addition, a regression model was used to determine the best kinematic and/or kinetic predictor of peak patella cartilage stress.
The PFP group exhibited significantly greater peak hydrostatic pressure and peak maximum shear stress. No between group differences were found for contact area or contact forces, and for any of the tibiofemoral joint kinematic or kinetic variables of interest. The