Video-based assessment of foot strike pattern and step rate is valid and reliable in runners with patellofemoral pain

Abstract

ObjectivesTo evaluate, during treadmill running in runners with patellofemoral pain (PFP), the concurrent validity of determining foot strike pattern using 2D video and the intra- and inter-rater reliability of foot strike pattern and step rate assessments between a novice and experienced observer. DesignMethodological study (validity/reliability). SettingMotion analysis laboratory. ParticipantsSixty runners with PFP (37 females, 23 males; age = 30.8 ± 6.5 years; height = 169.8 ± 9.1 cm; weight = 66.6 ± 12.9 kg). Main outcome measuresRunning kinematics were recorded using 3D motion capture and a sagittal view 2D video camera. Concurrent validity, intra-, and inter-rater reliability of foot strike pattern determination (Gwet AC statistics), and reliability of step rate calculation (Intraclass correlation coefficients, ICC) were assessed. ResultsFor foot strike pattern, agreement between the 3D motion analysis system and 2D video assessment was high for both raters (AC = 0.906–0.936, P < 0.001). Excellent intra (AC = 0.961–1.000, ICC = 0.984–0.998, respectively) and inter-rater reliability (AC = 0.929–0.970, ICC = 0.980, respectively) was obtained for foot strike pattern and step rate. ConclusionsVideo-based evaluation of foot strike pattern and step rate of runners with PFP is valid and highly reliable when performed by a novice or experienced assessor. Therefore, clinicians and researchers can use such methods confidently to guide their gait retraining interventions for runners with PFP.