title: Intraobserver and interobserver reliability of the kneeling technique of stress radiography for the evaluation of posterior knee laxity.
abstract: BACKGROUND
  Stress radiography provides an objective tool to measure posterior knee instability. Intraobserver and interobserver reliability has been reported for the Telos device, but it has not been studied using the kneeling technique.
  
  
  OBJECTIVE
  This study was conducted to evaluate the intraobserver and interobserver reliability of measurements made using kneeling stress radiography to quantify posterior knee instability.
  
  
  METHODS
  Case series (diagnosis); Level of evidence, 4.
  
  
  METHODS
  One hundred thirty-two stress radiographs in 44 patients with suspected posterior knee instability were prospectively taken using the kneeling technique. The amount of posterior displacement on the radiographs was then measured independently by 3 blinded testers (an orthopaedic sports medicine faculty member, an orthopaedic chief resident, and a medical student) on 2 separate occasions. Changes in mean and intraclass correlation coefficients (ICCs) were examined to assess the intraobserver and interobserver reliability of the measurements.
  
  
  RESULTS
  Intraobserver changes in displacement means were small (-0.307 mm, -0.294 mm, and +0.035 mm) and only significant for observer 1. The combined intraobserver ICC was 0.973 for the 3 observers (0.976, 0.959, and 0.981). Interobserver comparisons revealed significant differences in trial 1 between observers 2 and 3 (0.675 mm), no differences in trial 2, and significant differences between observers 1 and 2 (0.333 mm) and observers 2 and 3 (0.510 mm) in the combined trial data. The combined interobserver ICC was 0.955 for the 3 observers (0.959 and 0.951 for the 2 trials).
  
  
  CONCLUSIONS
  The kneeling technique for posterior cruciate ligament stress radiography provides a reproducible method to quantify posterior knee instability.
authors.affiliation: Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue, R200, Minneapolis, MN 55454, USA.
authors.forename: Todd
authors.initials: T
authors.lastname: Jackman
authors.forename: Robert F
authors.initials: RF
authors.lastname: LaPrade
authors.forename: Thomas
authors.initials: T
authors.lastname: Pontinen
authors.forename: Paul A
authors.initials: PA
authors.lastname: Lender
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging*; D007719:Knee Joint / Q000502:physiology*; D008875:Middle Aged; D015588:Observer Variation; D016119:Posterior Cruciate Ligament; D011187:Posture; D011446:Prospective Studies; D011859:Radiography / Q000295:instrumentation; D015203:Reproducibility of Results; D013314:Stress, Mechanical