Three-dimensional joint kinematic and two-dimensional quality of movement comparison between lateral and forward step-downs

Objectives: While lateral and forward step-down tasks are commonly used, they may have different kinematic and performance demands that could influence clinical assessment and rehabilitation. Therefore, the purpose of this study was to compare 3D lower extremity kinematics and 2D quality of movement between the tasks. Design: Cross-sectional comparative study. Setting: Research laboratory. Participants: Thirty healthy adults (18 females, age = 23.2 +/- 1.4 years, BMI = 23.9 +/- 2.2 kg/m2). Main outcome measures: Participants underwent 3D and 2D motion analysis. 3D variables were peak hip, knee, and ankle angles. Dichotomous clinical criteria were used for 2D assessment. An alpha level of 0.05 was used for statistical analyses. Results: In the sagittal plane, the forward step-down averaged 7 degrees more knee flexion (p < 0.001, d = 2.30) and 4 degrees more ankle dorsiflexion (p < 0.001, d = 1.72), but 2 degrees less hip flexion (p = 0.001, d = 0.64). In the frontal plane, forward step-downs averaged 1 degrees more hip adduction (p = 0.006, d = 0.54) and 1 degrees more ankle eversion (p < 0.001, d = 1.04). The forward step-down elicited 2D movement faults more often (p = 0.003). Conclusions: The increased knee flexion and ankle dorsiflexion demands of the forward step-down were accompanied by increases in frontal plane aberrations. The forward step-down may be more challenging for individuals with reduced tolerance to loaded knee flexion and/or limited ankle mobility. (C) 2021 Elsevier Ltd. All rights reserved.