title: Does knee osteoarthritis differentially modulate proprioceptive acuity in the frontal and sagittal planes of the knee?
abstract: OBJECTIVE
  Impaired proprioception may alter joint loading and contribute to the progression of knee osteoarthritis (OA). Although frontal plane loading at the knee contributes to OA, proprioception and its modulation with OA in this direction have not been examined. The aim of this study was to assess knee proprioceptive acuity in the frontal and sagittal planes in patients with knee OA and healthy subjects. We hypothesized that proprioceptive acuity in both planes of movement will be decreased in patients with OA.
  
  
  METHODS
  The study group comprised 13 patients with knee OA and 14 healthy age-matched subjects. Proprioceptive acuity was assessed in varus, valgus, flexion, and extension using threshold to detection of passive movement (TDPM) tests. Repeated-measures analysis of variance was used to assess differences in TDPM values between the 2 groups and across movement directions. Linear regression analyses were performed to assess the correlation of the TDPM between and within planes of movement.
  
  
  RESULTS
  The TDPM was significantly higher (P<0.05) in the group with knee OA compared with the control group for all directions tested, indicating reduced proprioceptive acuity. Differences in the TDPM between groups were consistent across all movement directions, with mean differences as follows: for valgus, 0.94° (95% confidence interval [95% CI] 0.20-1.65°); for varus, 0.92° (95% CI 0.18-1.68°); for extension, 0.93° (95% CI 0.19-1.66°); for flexion, 1.11° (95% CI 0.38-1.85°). The TDPM measures across planes of movement were only weakly correlated, especially in the group with knee OA.
  
  
  CONCLUSIONS
  Consistent differences in the TDPM between the group of patients with knee OA and the control group across all movement directions suggest a global, not direction-specific, reduction in sensation in patients with knee OA.
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois 60611, USA. m-cammarata@u.northwestern.edu
authors.forename: Martha L
authors.initials: ML
authors.lastname: Cammarata
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Schnitzer
authors.forename: Yasin Y
authors.initials: YY
authors.lastname: Dhaher
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007717:Knee / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D011434:Proprioception / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology