title: Cartilage shear dynamics during tibio-femoral articulation: effect of acute joint injury and tribosupplementation on synovial fluid lubrication.
abstract: OBJECTIVE
  To determine the effects of acute injury and tribosupplementation by hyaluronan (HA) on synovial fluid (SF) modulation of cartilage shear during tibio-femoral articulation.
  
  
  METHODS
  Human osteochondral blocks from the lateral femoral condyle (LFC) and tibial plateau (LTP) were apposed, compressed 13%, and subjected to sliding under video microscopy. Tests were conducted with equine SF from normal joints (NL-SF), SF from acutely injured joints (AI-SF), and AI-SF to which HA was added (AI-SF+HA). Local and overall shear strain (E(xz)) and the lateral displacement (Deltax) at which E(xz) reached 50% of peak values (Deltax(1/2)) were determined.
  
  
  RESULTS
  During articulation, LFC and LTP cartilage E(xz) increased with Deltax and peaked when surfaces slid, with peak E(xz) being maintained during sliding. With AI-SF as lubricant, surface and overall Deltax(1/2) were approximately 40% and approximately 20% higher, respectively, than values with NL-SF and AI-SF+HA as lubricant. Also, peak E(xz) was markedly higher with AI-SF as lubricant than with NL-SF as lubricant, both near the surface (approximately 80%) and overall (50-200%). Following HA supplementation to AI-SF, E(xz) was reduced from values with AI-SF alone by 30-50% near the surface and 20-30% overall. Magnitudes of surface and overall E(xz) were markedly (approximately 50 to 80%) higher in LTP cartilage than LFC cartilage for all lubricants.
  
  
  CONCLUSIONS
  Acute injury impairs SF function, elevating cartilage E(xz) markedly during tibio-femoral articulation; such elevated E(xz) may contribute to post-injury associated cartilage degeneration. Since HA partially restores the function of AI-SF, as indicated by E(xz), tribosupplements may be beneficial in modulating normal cartilage homeostasis.
authors.affiliation: Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093-0412, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Wong
authors.forename: S H Chris
authors.initials: SH
authors.lastname: Kim
authors.forename: J M
authors.initials: JM
authors.lastname: Antonacci
authors.forename: C Wayne
authors.initials: CW
authors.lastname: McIlwraith
authors.forename: R L
authors.initials: RL
authors.lastname: Sah
mesh_terms: D000328:Adult; D002358:Cartilage, Articular / Q000293:injuries* / Q000503:physiopathology; D005260:Female; D006801:Humans; D006820:Hyaluronic Acid / Q000378:metabolism*; D007596:Joints / Q000293:injuries* / Q000503:physiopathology; D007718:Knee Injuries / Q000503:physiopathology; D008153:Lubrication; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D033081:Shear Strength / Q000502:physiology; D013582:Synovial Fluid / Q000378:metabolism* / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D006820:Hyaluronic Acid