Oslo Sports Trauma Research Center

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Information about project titled 'Validation of the visual inspection approach in video analysis'

Validation of the visual inspection approach in video analysis

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Project status: Published
Project manager: Tron Krosshaug
Supervisor(s): Roald Bahr
Coworker(s): Atsuo Nakamae, Barry Boden, Lars Engebretsen, Gerald Smith, James Slauterbeck, Tim Hewett


Our current understanding of the mechanisms of non-contact ACL (anterior cruciate ligament) injuries originates in large part from the analysis of videotapes of injuries. In all these studies a visual inspection approach was used, where the joint angles and other kinematic variables were estimated simply from watching videotapes of ACL ruptures, without employing any measurement tools. Although our group has recently developed a more sophisticated method to estimate joint kinetics from video sequences, this is too time-consuming to apply on a large number of injury tapes. Simple visual assessment of joint kinematics may therefore be an alternative if the number of videos to be analyzed is large. However, the accuracy and precision of such analyses are unknown. Therefore, the purpose of this study was to test the accuracy and precision of researchers to estimate kinematics from video sequences of situations that typically lead to ACL injuries. We also tested if accuracy and precision could be improved by a training program.


Methods: Using a traditional surface marker based infrared, 240 Hz, 3D motion analysis system, we recorded running and cutting trials from three test subjects. Six international researchers were asked to provide estimates of kinematic variables from 27 video composites from one, two or three ordinary cameras, systematically varying viewing angles and time point of analysis. The analysts thereafter went through a training program where 35 similar composites were analyzed, and feedback on the kinematics as measured by the 3D motion analysis system was provided on a group basis. Finally, the pre-test was repeated to test for accuracy and precision.

The mean error for knee flexion was -19°, indicating a consistent underestimation. Hip flexion was underestimated by 7°, but the standard deviation between the analysts was 18° on average, indicating poor precision. Substantial errors were also found in the accuracy and precision of the other estimates. Only small group effects were seen from our training program.

Based on these findings, results from studies using a simple visual inspection approach to describe joint motion must be interpreted with caution.