title: Identifying multiplanar knee laxity profiles and associated physical characteristics.
abstract: BACKGROUND
  A single measure of knee laxity (ie, measurement of laxity in a single plane of motion) is probably inadequate to fully describe how knee joint laxity is associated with anterior cruciate ligament injury.
  
  
  OBJECTIVE
  To characterize interparticipant differences in the absolute and relative magnitudes of multiplanar knee laxity (ie, sagittal, frontal, and transverse planes) and examine physical characteristics that may contribute to these differences.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  140 participants (90 women, 50 men).
  
  
  METHODS
  Using cluster analysis, we grouped participants into distinct multiplanar knee laxity profiles based on the absolute and relative magnitudes of their anterior knee laxity (AKL), genu recurvatum (GR), and varusvalgus (VV) and internal-external rotation (IER) knee laxity. Using multinomial logistic regression, we then examined associations between the different laxity profile clusters and physical characteristics of sex, age, activity level, general joint laxity, body mass index, thigh strength, and 8 measures of lower extremity anatomical alignment.
  
  
  RESULTS
  Six clusters were identified: low (LOW), moderate (MOD) and high (HIGH) laxity overall and disproportionally higher VV/IER (MOD(VV/IER)), GR (HIGH(GR)), and AKL (HIGH(AKL)) laxity. Once all other physical characteristics were accounted for, the LOW cluster was more likely to be older, with longer femur length. Clusters with greater magnitudes of VV and IER laxity were more likely to be younger and to have lower body mass index, smaller Q-angle, and shorter femur length (MOD, HIGH, MOD(VV/IER)) and less thigh strength (HIGH). The HIGH(GR) cluster was more likely to be female and to have a smaller tibiofemoral angle and longer femur length. The HIGH(AKL) cluster was more likely to have greater hip anteversion and navicular drop.
  
  
  CONCLUSIONS
  The absolute and relative magnitudes of a person's multiplanar knee laxity are not always uniform across planes of motion and can be influenced by age, body composition, thigh strength, and structural alignment. Except in HIGH(GR), sex was not a significant predictor of cluster membership once other physical characteristics were taken into account.
authors.affiliation: Applied Neuromechanics Research Laboratory, Department of Kinesiology, 1408 Walker Avenue, Greensboro, NC 27402, USA. sjshultz@uncg.edu
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shultz
authors.forename: William N
authors.initials: WN
authors.lastname: Dudley
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Kong
mesh_terms: D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability; D007717:Knee; D007718:Knee Injuries; D007719:Knee Joint / Q000502:physiology*; D035002:Lower Extremity; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology; D012737:Sex Factors; D055815:Young Adult