title: Rotational knee laxity: reliability of a simple measurement device in vivo.
abstract: BACKGROUND
  Double bundle ACL reconstruction has been demonstrated to decrease rotational knee laxity. However, there is no simple, commercially-available device to measure knee rotation. The investigators developed a simple, non-invasive device to measure knee rotation. In conjunction with a rigid boot to rotate the tibia and a force/moment sensor to allow precise determination of torque about the knee, a magnetic tracking system measures the axial rotation of the tibia with respect to the femur. This device has been shown to have acceptable levels of test re-test reliability to measure knee rotation in cadaveric knees.
  
  
  METHODS
  The objective of this study was to determine reliability of the device in measuring knee rotation of human subjects. Specifically, the intra-tester reliability within a single testing session, test-retest reliability between two testing sessions, and inter-tester reliability were assessed for 11 male subjects with normal knees.
  
  
  RESULTS
  The 95% confidence interval for rotation was less than 5 degrees for intra-tester, test-retest, and inter-tester reliability, and the standard error of measurement for the differences between left and right knees was found to be less than 3 degrees .
  
  
  CONCLUSIONS
  It was found that the knee rotation measurements obtained with this device have acceptable limits of reliability for clinical use and interpretation.
authors: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA. andrew.g.tsai@gmail.com
authors: Andrew G
authors: AG
authors: Tsai
authors: Volker
authors: V
authors: Musahl
authors: Hanno
authors: H
authors: Steckel
authors: Kevin M
authors: KM
authors: Bell
authors: Thore
authors: T
authors: Zantop
authors: James J
authors: JJ
authors: Irrgang
authors: Freddie H
authors: FH
authors: Fu
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology; D053587:Arthrometry, Articular / Q000295:instrumentation* / Q000379:methods; D001696:Biomechanical Phenomena; D003196:Computer Graphics; D004867:Equipment Design; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008280:Magnetics / Q000295:instrumentation*; D008297:Male; D015588:Observer Variation; D016059:Range of Motion, Articular; D012016:Reference Values; D015203:Reproducibility of Results; D012399:Rotation; D013977:Tibia / Q000502:physiology; D019415:Torque