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

Objectives: To 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.

Design: Methodological study (validity/reliability).

Setting: Motion analysis laboratory.

Participants: Sixty 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 Measures: Running 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.

Results: For 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.

Conclusions: Video-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.