Dynamics of Synovial Fluid Aggregation under Shear

Abstract

The synovial fluid (SF) that lubricates articular joints exhibits complex rheological and tribological properties due to the interactions and behaviors of its various molecular components. Under shear, SF films abruptly thicken by more than 300% and large, dense aggregates form within the fluid. In this study, we used the Surface Force Apparatus to elucidate which SF components are involved in this shear-induced transformation by (i) determining which (if any) of all major SF components replicate the behavior of SF under shear and (ii) observing the effect of removing implicated components from SF by enzymatic digestion. While most previous studies of SF have focused on the tribological roles of lubricin or hyaluronic acid, our results indicate that albumin is a key contributor to the formation of aggregates in SF under shear. Our results also suggest that SF aggregation is associated with efficient surface protection against wear. As our findings are based on experiments involving rigid, nonporous surfaces, they may be used to investigate shear-mediated aggregation mechanisms occurring during the lubrication of artificial joints, ultimately advancing our current vision of implant design.

Glycosaminoglycans and glycoproteins influence the elastic response of synovial fluid nanofilms on model oxide surfaces

“…To cleave GAGs in SF, centrifuged and undiluted SF was treated with 2 µL of 1.25 mg/mL hyaluronidase (HAase) from bovine testes (Sigma, H3506) for every 50 µL of SF, following established protocols. [7,30] SF plus the hyaluronidase were placed on a shaker for 1.5 to 2 hrs., followed by a second centrifugation step, 5 min at 6000 rpm, and the suspension transferred to a new tube. This condition is referred to from now on as SF+HAase.…”

“…This prevents adhesion, [5] and when the surfaces are in relative motion, provides wear protection and lubrication. [6,7] The ability of specific SF components to adsorb to surfaces is crucial to build and control the supramolecular assembly of an effective load-bearing, wear-protecting, and lubricating film. Without it, molecules would be squeezed out from the junction at the high contact (normal) loads experienced during locomotion (~10-15 MPa).…”

Rheological Properties and Its Effect on the Lubrication Mechanism of PVP K30 and PVP 40-50 G as Artificial Synovial Fluids

“…Its major functions include cushioning and steady load absorption during loading and providing a minimum coefficient of friction for smooth movement between the bones of the joint [2]. This behavior of synovial fluid is attributed to its viscoelastic-shear thinning fluid, which is mainly due to the presence of hyaluronic acid (HA), lubricin, serum albumin, and globulin [3]. The interaction between these molecules results in synovial fluid's boundary layer formation during less shear and elasto-hydrodynamic behavior during high shear [4].…”

Preparation and characterization of imidazolyl ionic liquid‐based shear thickening dispersion system

“…Severe shear thickening in pipeline transportation brought about pipe blockage and even damage to production equipment. [4][5][6] Various practical problems have aroused people's attention to shear thickening phenomenon. In recent years, researchers have conducted in-depth studies on the composition, performance characterization, influencing factors and mechanism of shear thickening liquid, and preliminarily grasped the causes and mechanism of shear thickening.…”

“…In the early development of industrial production, it was found that shear thickening often led to the deterioration of fluid flow, obstructing the uniform coating of coating materials. Severe shear thickening in pipeline transportation brought about pipe blockage and even damage to production equipment 4–6 . Various practical problems have aroused people's attention to shear thickening phenomenon.…”