title: The effect of age-related declines in proprioception and total knee replacement on postural control.
abstract: BACKGROUND
  An experiment was designed to examine the effects of a decrease in threshold joint position sense (TJPS) at the knee and ankle and of total knee replacement (TKR) on postural control in older adults. It was hypothesized that older adults with a decrease in TJPS and those who had undergone TKR would display increased center of pressure (COP) variance during quiet stance and late onsets for muscle responses to balance threats.
  
  
  METHODS
  Older adult subjects (> or = 70 years) were evaluated and grouped according to the status of their ankle and knee threshold joint position sensation as well as their surgical history. COP data were collected while subjects stood on a force plate with feet together under eyes-open and -closed conditions. Threats to balance were given using a platform that moved forward and backward.
  
  
  RESULTS
  Older subjects with poor knee extension TJPS had significantly increased COP variance, although those with very poor knee flexion and extension TJPS demonstrated even greater increases. Similarly, subjects with decreased ankle TJPS demonstrated increased COP variance. However, reduced TJPS did not affect the ability of subjects to respond to threats to balance. Post-TKR subjects showed no reductions in any aspect of postural control.
  
  
  CONCLUSIONS
  This study showed that the task of standing quietly has a direct relationship to threshold JPS, although the task of recovering from an abrupt perturbation does not. Older adult TKR results suggest that there is no negative effect on balance from elective joint replacement.
authors.affiliation: Department of Exercise and Movement Science, University of Oregon, Eugene, USA. jmcches@boisestate.edu
authors.forename: J W
authors.initials: JW
authors.lastname: McChesney
authors.forename: M H
authors.initials: MH
authors.lastname: Woollacott
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology*; D000842:Ankle / Q000502:physiology; D019645:Arthroplasty, Replacement, Knee; D004576:Electromyography; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D011187:Posture; D011434:Proprioception