title: Altered visual and feet proprioceptive feedbacks during quiet standing increase postural sway in patients with severe knee osteoarthritis.
abstract: OBJECTIVE
  The objective was to investigate how postural control in knee osteoarthritis (KOA) patients, with different structural severities and pain levels, is reorganized under different sensory conditions.
  
  
  METHODS
  Forty-two obese patients (BMI range from 30.1 to 48.7 kg*m(-2), age range from 50 to 74 years) with KOA were evaluated. One minute of quiet standing was assessed on a force platform during 4 different sensory conditions, applied 3 times at random: Eyes open (EO) and eyes closed (EC) standing on firm and soft (foam) surfaces (EO-soft and EC-soft). Centre of pressure (Cop) standard deviation, speed, range and Cop mean position in both directions (anterior-posterior and medial-lateral) were extracted from the force platform data. Structural disease severity was assessed from semiflexed standing radiographs and graded by the Kellgren and Lawrence (KL) score. Pain intensity immediately before the measurements was assessed by numeric rating scale (range: 0-10).
  
  
  RESULTS
  The patients were divided into "less severe" (KL 1 and 2, n = 24) and "severe" (KL>2, n = 18) group. The CoP range in the medial-lateral direction was larger in the severe group when compared with the less severe group during EC-soft condition (P<0.01). Positive correlation between pain intensity and postural sway (range in medial-lateral direction) was found during EC condition, indicating that the higher the pain intensity, the less effective is the postural control applied to restore an equilibrium position while standing without visual information.
  
  
  CONCLUSIONS
  THE RESULTS SUPPORT THAT: (i) the postural reorganization under manipulation of the different sensory information is worse in obese KOA patients with severe degeneration and/or high pain intensity when compared with less impaired patients, and (ii) higher pain intensity is related to worse body balance in obese KOA patients.
authors.affiliation: Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Aalborg, Denmark.
authors.forename: Rogerio Pessoto
authors.initials: RP
authors.lastname: Hirata
authors.forename: Tanja Schjødt
authors.initials: TS
authors.lastname: Jørgensen
authors.forename: Sara
authors.initials: S
authors.lastname: Rosager
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Henning
authors.initials: H
authors.lastname: Bliddal
authors.forename: Marius
authors.initials: M
authors.lastname: Henriksen
authors.forename: Thomas
authors.initials: T
authors.lastname: Graven-Nielsen
mesh_terms: D000368:Aged; D015992:Body Mass Index; D056228:Feedback, Sensory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D010146:Pain; D004856:Postural Balance; D011312:Pressure; D011434:Proprioception / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D014785:Vision, Ocular; D014796:Visual Perception / Q000502:physiology*