High Agreement Between 3D Motion Capture and 2D Video Analysis Systems and Raters for Knee Flexion Range of Motion During a Single-Leg Drop Landing Task

OBJECTIVE: To determine the agreement between a two-dimensional (2D) and three-dimensional (3D) video capture system and between multiple raters during a single-leg drop landing task. DESIGN: Cross-sectional observational study. METHODS: Single-leg drop landing trials of 23 males (n = 12) and females (n = 11) were recorded using the 2D and 3D systems. Reliability and agreement were quantified through intraclass correlation coefficients (ICC 2, k ), standard error of the measurement (SEM), and Bland-Altman plots. Analysis of variance assessed systematic error between the 2D raters and 3D system. RESULTS: A 1-way analysis of variance on 35 drop-landing trials across raters detected a difference across the 3 estimates of knee flexion range of motion ( P<.001) where rater 1 did not differ (mean difference ± standard error: 1.15° ± 0.48°, P = .54) from the 3D system, rater 2 > 3D system (3.30° ± 0.76°, P<.001), and raters 1 and 2 differed (2.14° ± 0.82°, P = .04). There was high reliability between the two 2D raters (ICC 2, k = .89, SEM = 3.44°). Rater 1 completed analyses on 87 additional trials (total n = 117) and was comparable to the 3D system (0.87° ± 0.47°, P = .06; ICC 2, k = .90; SEM = 3.52°). CONCLUSION: Two-dimensional video analysis can be used in a clinical setting where 3D capture of movement mechanics is not feasible. JOSPT Open 2025;3(1):69-76. Epub 10 September 2024. doi:10.2519/josptopen.2024.0051