Cartilage shear dynamics during tibio-femoral articulation: effect of acute joint injury and tribosupplementation on synovial fluid lubrication

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 (Delta x) at which E-xz reached 50% of peak values (Delta x(1/2)) were determined. Results: During articulation, LFC and LTP cartilage E-xz increased with Delta x and peaked when surfaces slid, with peak E-xz being maintained during sliding. With AI-SF as lubricant, surface and overall Delta X-1/2 were similar to 40% and similar to 20% higher, respectively, than values with NL-SF and AI-SF + HA as lubricant. Also, peak Ex, was markedly higher with AI-SF as lubricant than with NL-SF as lubricant, both near the surface (similar to 80%) and overall (50-200%). Following HA supplementation to AI-SF, Exz was reduced from values with AI-SF alone by 30-50% near the surface and 20-30% overall. Magnitudes of surface and overall E., were markedly (similar to 50 to 80%) higher in LTP cartilage than LFC cartilage for all lubricants. Conclusion: Acute injury impairs SF function, elevating cartilage E., markedly during tibio-femoral articulation; such elevated E, 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. (C) 2009 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.