title: Evaluation of unipodal stance in knee osteoarthritis patients using knee accelerations and center of pressure.
abstract: OBJECTIVE
  This study aims to compare knee joint instability and postural impairments during the performance of a unipodal stance task between patients having knee osteoarthritis (OA) and healthy elderly subjects using knee accelerations and center of pressure (COP) measurements.
  
  
  METHODS
  Twenty patients with medial knee OA and nine healthy individuals participated in this study. Three-dimensional (3D) knee joint accelerations and COP were measured during unipodal stance. The range and the root mean square (RMS) were extracted from medial lateral (ML) and anterior-posterior (AP) knee accelerations, whereas sway area, velocity, and ML and AP ranges were measured from the COP. The average parameters of three trials for each subject were compared between groups.
  
  
  RESULTS
  Results show that knee OA patients exhibited a significantly higher range of knee acceleration in both ML (0.22±0.08 g vs 0.15±0.05 g) and AP (0.17±0.06 g vs 0.06±0.01 g) directions and a lower COP velocity (136.6±22.3 mm/s vs 157.6±18.4 mm/s) than did the healthy age-matched group. Significant correlations between the COP and knee acceleration parameters were also obtained.
  
  
  CONCLUSIONS
  This study confirmed that patients with knee OA displayed greater body sway than did able-bodied subjects. Moreover, using an accelerometric-based method, this study highlighted the higher knee joint instability in the frontal and sagittal planes in knee OA patients compared with able-bodied subjects during a unipodal standing task.
authors.affiliation: Willy Taillard Laboratory of Kinesiology, Geneva University Hospitals and Geneva University, Switzerland. kturcot@gmail.com
authors.forename: K
authors.initials: K
authors.lastname: Turcot
authors.forename: N
authors.initials: N
authors.lastname: Hagemeister
authors.forename: J A
authors.initials: JA
authors.lastname: de Guise
authors.forename: R
authors.initials: R
authors.lastname: Aissaoui
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology* / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications* / Q000503:physiopathology*; D004856:Postural Balance; D011187:Posture; D016474:Weight-Bearing / Q000502:physiology