title: The effect of a passive muscle stretching protocol on the articular cartilage.
abstract: OBJECTIVE
  The aim of this study is to evaluate the articular cartilage alterations of rat ankles, after applying unilateral cyclic passive muscle stretching protocol in previously immobilized rats.
  
  
  METHODS
  Twenty-two male albino rats divided into four groups, I--immobilized; IS--immobilized and stretched; S--stretched and C--control, were used in this experiment. The I and IS groups were immobilized for 4 weeks. In the muscle stretching protocol the treated ankle joint (groups IS and S) was manually full dorsal flexed 10 times for 60s with a 30s interval between each 60s period, 7 days a week for 3 weeks, to stretch the ankle plantar flexors muscle group. The right hind limb was free to move. At the end of the experiment, the ankles were removed, processed in paraffin and stained with hematoxylin-eosin and Safranin-O. Two blinded observers evaluated cellularity, chondrocyte cloning and Safranin-O staining through light microscopy. And a morphometric study was carried out using a hand count of chondrocyte cells and cartilage thickness measurement.
  
  
  RESULTS
  No significant effect of solely muscle stretching concerning cellularity, chondrocyte cloning and Safranin-O staining parameters was detected. However, IS group presented a significantly higher reduction of proteoglycans content than the solely stretched and solely immobilized groups and the morphometric analysis showed significant cellularity increase without thickness alteration compared to control.
  
  
  CONCLUSIONS
  These findings suggest that the stretching protocol used was harmful to the previously immobilized articular cartilage. However, the same stretching protocol did not harm the cartilage of non-immobilized groups.
authors.affiliation: Department of Physiotheraphy, Federal University of São Carlos, São Paulo, Brazil.
authors.forename: A F
authors.initials: AF
authors.lastname: Renner
authors.forename: E
authors.initials: E
authors.lastname: Carvalho
authors.forename: E
authors.initials: E
authors.lastname: Soares
authors.forename: S
authors.initials: S
authors.lastname: Mattiello-Rosa
mesh_terms: D000818:Animals; D002358:Cartilage, Articular / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D002452:Cell Count; D019902:Chondrocytes / Q000378:metabolism / Q000473:pathology; D006614:Hindlimb; D007103:Immobilization; D007551:Isotonic Contraction; D007596:Joints / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D026741:Physical Therapy Modalities / Q000009:adverse effects*; D011509:Proteoglycans / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D011509:Proteoglycans