title: Knee rotational laxity: an investigation of bilateral asymmetry for comparison with the contralateral uninjured knee.
abstract: BACKGROUND
  Instability associated with anterior cruciate ligament injury is commonly evaluated against the patient's contralateral knee. The objectives of this study were, therefore, to assess symmetry of rotational knee laxity in vivo under passive torsional loading in uninjured subjects, and to compare mean rotation of this control group with the contralateral, intact knees of anterior cruciate ligament deficient patients.
  
  
  METHODS
  Axial knee rotation was measured in 29 patients with unilateral anterior cruciate ligament injury and 15 uninjured age and gender-matched control subjects using an imaging-compatible torsional loading device. Side-to-side differences in internal, external, and range of knee rotation were assessed in the control group and mean bilateral knee rotation was compared to the patients' contralateral knee data at both full extension and 30° of flexion.
  
  
  RESULTS
  Statistically significant differences in symmetry were found in three of the six measures of transverse plane rotation in the uninjured knees; a mean side-to-side difference of 2.2° in range of rotation was detected in the flexed position. No significant differences were observed between the mean values of the healthy control group and the contralateral knees of the anterior cruciate ligament deficient patients.
  
  
  CONCLUSIONS
  Bilateral asymmetry of rotational laxity occurs in healthy individuals. Nevertheless, comparability of rotational knee laxity between the contralateral limbs of patients and the uninjured population was evidence that rotational laxity was not inherent or developed in the contralateral knees of the anterior cruciate ligament deficient participants.
authors.affiliation: Department of Human Biology, University of Cape Town, South Africa. a.hemmerich@alumni.utoronto.ca
authors.forename: A
authors.initials: A
authors.lastname: Hemmerich
authors.forename: W
authors.initials: W
authors.lastname: van der Merwe
authors.forename: M
authors.initials: M
authors.lastname: Batterham
authors.forename: C L
authors.initials: CL
authors.lastname: Vaughan
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D004867:Equipment Design; D005260:Female; D006801:Humans; D007717:Knee / Q000033:anatomy & histology / Q000502:physiology*; D007718:Knee Injuries / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008953:Models, Anatomic; D015233:Models, Statistical; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D012737:Sex Factors; D013314:Stress, Mechanical; D019415:Torque