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

SummaryObjectiveTo determine the effects of acute injury and tribosupplementation by hyaluronan (HA) on synovial fluid (SF) modulation of cartilage shear during tibio-femoral articulation.MethodsHuman 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 (Exz) and the lateral displacement (Δx) at which Exz reached 50% of peak values (Δx1/2) were determined.ResultsDuring articulation, LFC and LTP cartilage Exz increased with Δx and peaked when surfaces slid, with peak Exz being maintained during sliding. With AI-SF as lubricant, surface and overall Δx1/2 were ∼40% and ∼20% higher, respectively, than values with NL-SF and AI-SF + HA as lubricant. Also, peak Exz was markedly higher with AI-SF as lubricant than with NL-SF as lubricant, both near the surface (∼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 Exz were markedly (∼50 to 80%) higher in LTP cartilage than LFC cartilage for all lubricants.ConclusionAcute injury impairs SF function, elevating cartilage Exz markedly during tibio-femoral articulation; such elevated Exz may contribute to post-injury associated cartilage degeneration. Since HA partially restores the function of AI-SF, as indicated by Exz, tribosupplements may be beneficial in modulating normal cartilage homeostasis.