title: Extent and direction of joint motion limitation after prolonged immobility: an experimental study in the rat.
abstract: OBJECTIVE
  To test the hypotheses that contractures progress at different rates in relation to the time after immobilization, that immobilization in flexion leads to loss of extension range of motion, and that joints of sham-operated animals are better controls than the contralateral joint of experimental animals.
  
  
  METHODS
  Experimental, controlled study in which 40 adult rats had one knee joint immobilized at 135 degrees of flexion for up to 32 weeks and 20 animals underwent a sham procedure. At intervals of 2, 4, 8, 16, and 32 weeks, 8 experimental and 4 sham-operated animals were killed and their knee motion measured in flexion and extension.
  
  
  RESULTS
  In the experimental group, the range of motion decreased in the first 16 weeks of immobility at an average rate of 3.8 degrees per week (p<.0001) to reach 61.1 degrees of restriction. A plateau was then observed from which the contracture did not progress further. The loss in range of motion occurred in extension, not in flexion.
  
  
  CONCLUSIONS
  This study defined an acute stage of contractures starting at the onset of immobility and lasting 16 weeks, during which the range of motion was progressively restricted, and a chronic stage during which no additional limitation was detected. The loss in motion was attributed to posterior knee structures not under tension during immobilization in flexion. Contrary to the hypothesis, the contralateral joint was validated as a control choice for range-of-motion experiments.
authors.affiliation: Department of Medicine, University of Ottawa, and the Institute for Rehabilitation Research and Development, Ontario, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Trudel
authors.forename: H K
authors.initials: HK
authors.lastname: Uhthoff
authors.forename: M
authors.initials: M
authors.lastname: Brown
mesh_terms: D000208:Acute Disease; D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D002908:Chronic Disease; D003286:Contracture / Q000209:etiology* / Q000503:physiopathology*; D004195:Disease Models, Animal; D018450:Disease Progression; D007103:Immobilization / Q000009:adverse effects*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D016059:Range of Motion, Articular; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors