title: Frictional properties of Hartley guinea pig knees with and without proteolytic disruption of the articular surfaces.
abstract: OBJECTIVE
  To apply a pendulum technique to detect changes in the coefficient of friction of the articular cartilage of the intact guinea pig tibiofemoral joint after proteolytic disruption.
  
  
  METHODS
  Twenty-two hind limbs were obtained from 11 3-month old Hartley guinea pigs. Twenty knees were block-randomized to one of two treatment groups receiving injections of: (1) alpha-chymotrypsin (to disrupt the superficial layer of the articular surface) or (2) saline (sham; to control for the effects of the intra-articular injection). The legs were mounted in a pendulum where the knee served as the fulcrum. The decay in pendulum amplitude as a function of oscillation number was first recorded and the coefficient of friction of the joint was determined from these data before injection. Ten microliters of either isotonic saline or 1 Unit/microL alpha-chymotrypsin was then injected into the intra-articular joint space and incubated for 2h. The pendulum test was repeated. Changes in the coefficient of friction between the sham and alpha-chymotrypsin joints were compared. One additional pair of knees was used for histological study of the effects of the injections.
  
  
  RESULTS
  Treatment with alpha-chymotrypsin significantly increased the coefficient of friction of the guinea pig knee by 74% while sham treatment decreased it by 8%. Histological sections using Gomori trichrome stain verified that the lamina splendens was damaged following treatment with alpha-chymotrypsin and not following saline treatment.
  
  
  CONCLUSIONS
  Treatment with alpha-chymotrypsin induces mild cartilage surface damage and increases the coefficient of friction in the Hartley guinea pig knee.
authors.affiliation: Bioengineering Laboratory, Department of Orthopaedics, Brown Medical School/Rhode Island Hospital, Providence, RI 02903, USA.
authors.forename: E
authors.initials: E
authors.lastname: Teeple
authors.forename: B C
authors.initials: BC
authors.lastname: Fleming
authors.forename: A P
authors.initials: AP
authors.lastname: Mechrefe
authors.forename: J J
authors.initials: JJ
authors.lastname: Crisco
authors.forename: M F
authors.initials: MF
authors.lastname: Brady
authors.forename: G D
authors.initials: GD
authors.lastname: Jay
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena / Q000379:methods; D002358:Cartilage, Articular / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D002918:Chymotrypsin / Q000494:pharmacology*; D017276:Friction; D006168:Guinea Pigs; D007270:Injections, Intra-Articular; D007719:Knee Joint / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D012697:Serine Endopeptidases / Q000494:pharmacology*
chemical_list: D012697:Serine Endopeptidases; D002918:Chymotrypsin; C117608:alpha-chymotrypsin