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Author Notes:

Email Address:Shaun Stinton :stinton@emory.edu



  • Knee laxity
  • Manual examination
  • Robotic testing
  • Reliability
  • Rotational laxity

Robotic axial lower leg testing: repeatability and reproducibility


Journal Title:

Knee Surgery, Sports Traumatology, Arthroscopy


Volume 23, Number 10


, Pages 2892-2899

Type of Work:

Article | Final Publisher PDF


© 2015, The Author(s). Purpose: The purpose of this study was to determine the test–retest reliability and the repeatability over multiple days of a robotic testing device when used to measure laxity of the lower leg during a simulated dial test. Methods: Ten healthy subjects were evaluated using an instrumented robotic lower leg testing system over 4 days. Three testing cycles were performed each day. Each leg was rotated into external and then internal rotation by servomotors until a torque threshold of 5.65 N m was reached. Load–deformation curves were generated from torque and rotation data. Both average-measure and single-measure intraclass correlation coefficients (ICC) were compared across the curves. ICC scores were also compared for features of the curves including: maximum external rotation at −5.65 N m of torque, maximum internal rotation at 5.65 N m of torque, rotation at torque 0, compliance (slope of load–deformation curve) at torque 0, endpoint compliance in external rotation, endpoint compliance in internal rotation, and play at torque 0. Play at torque 0 was defined as the width of the hysteresis curve at torque 0. Results: Average-measure ICC scores and test–retest scores were >0.95 along the entire load–deformation curve except around zero torque. ICC scores at maximum internal and external rotation ranged from 0.87 to 0.99 across the left and right knees. ICC scores for the other features of the curves ranged from 0.61 to 0.98. The standard error of the mean ranged from 0.0497 to 1.1712. Conclusions: The robotic testing device in this study proved to be reliable for testing a subject multiple times both within the same day and over multiple days. These findings suggest that the device can provide a level of reliability in rotational testing that allows for clinical use of test results. Objective laxity data can improve consistency and accuracy in diagnosing knee injuries and may enable more effective treatment.

Copyright information:

© The Author(s) 2015

This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits making multiple copies, distribution of derivative works, distribution, public display, and publicly performance, provided the original work is properly cited. This license requires credit be given to copyright holder and/or author, copyright and license notices be kept intact.

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