title: Evaluation of patellar tracking in patients with suspected patellar malalignment: cine MR imaging vs arthroscopy.
abstract: OBJECTIVE
  The purpose of this study was to compare results of motion-triggered cine MR imaging of active extension of the knee with arthroscopic findings in cases of suspected femoropatellar malalignment.
  
  
  METHODS
  Twenty patients with clinically proved or suspected patellar subluxation or dislocation were examined prospectively with motion-triggered cine MR imaging to analyze patellar tracking from 30 degrees of flexion to full extension during active extension of the knee. The patellar tracking pattern was evaluated by measuring the following: bisect offset and lateral patellar displacement to assess lateralization of the patella and the patellar tilt angle to assess tilting of patella. The slopes of the linear regression lines of the MR findings vs the knee angle position, representing the patellar tracking, and the position of the patella at 30 degrees and 0 degrees of flexion were correlated with a semiquantitative arthroscopic classification of patellar tracking that had four categories ranging from normal to highly abnormal.
  
  
  RESULTS
  The results showed a significant correlation between the semiquantitative arthroscopic findings of patellar tracking and the slopes of the linear regression lines of the bisect offset, lateral patellar displacement, and patellar tilt angle, as measured with cine MR imaging (p < .01). The arthroscopic findings also correlated significantly with the position of the patella when the knee was extended (p < .01), but not with the knee flexed 30 degrees.
  
  
  CONCLUSIONS
  We conclude that motion-triggered cine MR imaging of active extension of the knee enables the dynamic evaluation of patellar bracing and is therefore suitable for noninvasive analysis of patellar tracking.
authors.affiliation: Klinik für Radiologische Diagnostik, Christian Albrechts Universität, Kiel, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Brossmann
authors.forename: C
authors.initials: C
authors.lastname: Muhle
authors.forename: C C
authors.initials: CC
authors.lastname: Büll
authors.forename: C
authors.initials: C
authors.lastname: Schröder
authors.forename: U H
authors.initials: UH
authors.lastname: Melchert
authors.forename: J
authors.initials: J
authors.lastname: Zieplies
authors.forename: R P
authors.initials: RP
authors.lastname: Spielmann
authors.forename: M
authors.initials: M
authors.lastname: Heller
mesh_terms: D000328:Adult; D001182:Arthroscopy; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000175:diagnosis* / Q000453:epidemiology; D007718:Knee Injuries / Q000175:diagnosis* / Q000453:epidemiology; D007719:Knee Joint / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010329:Patella / Q000473:pathology / Q000503:physiopathology*; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology