title: Postural sway in single-limb and bilateral quiet standing after unilateral total knee arthroplasty.
abstract: OBJECTIVE
  To investigate whether total knee arthroplasty (TKA) was associated with stability in single-limb stance and whether reduced stability in single-limb stance was associated with increased postural sway in bilateral quiet standing.
  
  
  METHODS
  3D kinematics for center of mass was used to assess postural sway in 23 subjects with TKA and 23 controls. Tests included bilateral quiet standing with and without vision and on a compliant surface, and single-limb stance.
  
  
  RESULTS
  30% of the subjects in the TKA group were unable to maintain single-limb stance for 20s on any leg. Of the 70% in the TKA group able to stand on one leg, mean sway velocity in the medio-lateral direction was marginally higher for the prosthetic side (p=.02), but no differences were found between the TKA and the control group in single-limb stance. Performance in bilateral quiet standing was similar in TKA-subjects, able as well as unable to stand on one leg, and controls. Reduced quadriceps strength in the contralateral leg, higher BMI, and older age predicted failure to maintain single-limb stance.
  
  
  CONCLUSIONS
  In subjects able to stand on one leg, performance was considered comparable between the prosthetic and contralateral side and between groups. Inability to stand on one leg did not affect postural sway in bilateral quiet standing. The results suggest that inability to maintain single-limb stance is explained by reduced physical capacity rather than the knee condition in itself. The present study emphasizes the importance of physical activity to improve strength and functional capacity.
authors.affiliation: Department of Community Medicine & Rehabilitation Physiotherapy, Umeå University, Umeå, Sweden; Department of Physiotherapy, School of Health Education & Social Work, Sør-Trøndelag University College, Trondheim, Norway. Electronic address: ann-katrin.stensdotter@hist.no.
authors.forename: Ann-Katrin
authors.initials: AK
authors.lastname: Stensdotter
authors.affiliation: Department of Community Medicine & Rehabilitation Physiotherapy, Umeå University, Umeå, Sweden; Department of Physiotherapy, School of Health Education & Social Work, Sør-Trøndelag University College, Trondheim, Norway.
authors.forename: Joakim
authors.initials: J
authors.lastname: Bjerke
authors.affiliation: Centre for Musculoskeletal Research, Department of Occupational and Public Health Sciences, University of Gävle, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Djupsjöbacka
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*
keywords: Joint position sense; Postural control; Prosthesis; Quadriceps strength; Romberg