Effective viscous lubrication of cartilage with low viscosity microgels

Viscosupplementation is one of the primary treatments for osteoarthritis, with the goal of restoring the viscoelastic properties of native synovial fluid. Recent work shows a strong in vitro in vivo correlation between the lubricating abilities of viscosupplements and improved patient reported outcomes, suggesting new viscosupplement formulations need to achieve sufficient lubrication of cartilage to be clinically relevant. This study describes a library of low viscosity microgel suspensions that lubricate cartilage as if they were highly viscous lubricants. Microgel formulations were characterized by their size, rheological properties, and lubricating abilities. Microgels synthesized with low crosslinking density exhibited lubrication equivalent to bovine synovial fluid (mu = 0.037-0.064), while maintaining low measured viscosities similar to PBS (eta(10 s-1) = 2.04-4.71 mPa*s). These results set the foundation for a new era of viscosupplementation using low viscosity lubricants.