Viscosity Of Synovial Fluid Research Articles

Zwitterionic Poly-Carboxybetaine Polymers Restore Lubrication of Inflamed Articular Cartilage.

Osteoarthritis is a degenerative joint disease that is associated with decreased synovial fluid viscosity and increased cartilage friction. Though viscosupplements are available for decades, their clinical efficacy is limited and there is ample need for more effective joint lubricants. This study first evaluates the tribological and biochemical properties of bovine articular cartilage explants after stimulation with the inflammatory cytokine interleukin-1β. This model is then used to investigate the tribological potential of carboxybetaine (CBAA)-based zwitterionic polymers of linear and bottlebrush architecture. Due to their affinity for cartilage tissue, these polymers form a highly hydrated surface layer that decreases friction under high load in the boundary lubrication regime. For linear pCBAA, these benefits are retained over several weeks and the relaxation time of cartilage explants under compression is furthermore decreased, thereby potentially boosting the weeping lubrication mechanism. Bottlebrush bb-pCBAA shows smaller benefits under boundary lubrication but is more viscous than linear pCBAA, therefore providing better lubrication under low load in the fluid-film regime and enabling a longer residence time to bind to the cartilage surface. Showing how CBAA-based polymers restore the lost lubrication mechanisms during inflammation can inspire the next steps toward more effective joint lubricants in the future.

DMAR drug loaded in enzymatic poly-l-phenylalanine nanotubes reduce inflammation and cytotoxicity in human synoviocytes

We investigated the release of chloroquine (Clq) as a model DMAR drug encapsulated in enzyme-mediated polyphenylalanine nanotubes (Clq-Nt) using primary cultures of synovial cells from OA inpatients undergoing total knee replacement. The Clq-Nts were also embedded in an injectable vehicle containing hyaluronic acid (Clq-Nt-HA). Clq-Nt and Clq-Nt-HA samples reduced 62 and 37.5 % the concentration of IL-1β, respectively. For TNF-α the reduction was 38 and 26 %, and for IL-6 was 17.1 and 10 % for Clq-Nt and Clq-Nt-HA, respectively. Additionally, Clq-Nt and Clq-Nt-HA allowed cell viability and proliferation of the synoviocytes according to MTT and CaAM/EthD-1 assays after fifteen days exposure. Micrographs of crystal violet assay also assess the adequate morphologies for synoviocytes treated with Clq-loaded in the tubes. The production of intracellular radical oxygen species (ROS), and extracellular H2O2 and nitrites was also investigated with the inpatient synoviocyte cells with and without treatments which showed no significant differences. Additionally, the apparent viscosity with the shear rate and viscoelastic properties in the injectable fluid containing the encapsulated drug Clq-Nt-HA showed no significant variation with control viscous fluid with only HA, and it falls within the synovial fluid viscosity range for arthritis patients.

Effect of Significant Parameters on Squeeze Film Characteristics in Pathological Synovial Joints

Synovial joints are unique biological tribo-systems that allow for efficient mobility. Most of the synovial joint activities in the human body are accomplished due to the presence of synovial fluid. As a biological lubricant, synovial fluid lubricates the articular cartilage to minimize wear and friction. The key components of synovial fluid that give it its lubricating ability are lubricin, hyaluronic acid (HA), and surface-active phospholipids. Due to age and activities, synovial fluid and articular cartilages lose their properties, restricting synovial joint mobility and resulting in articular cartilage degradation, leading to the pathological synovial joint, which is a major cause of disability. In this context, synovial joint research remains significant. Even though synovial joint lubrication has been investigated, several problems linked to squeeze film lubrication need greater attention. The Newtonian model of squeeze film lubrication in synovial joints must be studied more extensively. This work aims to investigate squeeze film lubrication in diseased synovial joints. The lubrication and other properties of synovial fluid and the flow of synovial fluid in a diseased human knee joint are investigated theoretically in this work. We have investigated the effect of the synovial fluid viscosity and the effects of permeability and thickness of articular cartilage on squeeze film properties. Moreover, we have also investigated the effect of squeeze velocity and film thickness on the characteristics of the squeeze film formed between the articular cartilages of a diseased human knee joint. In this work, the articular cartilages were treated as a rough, porous material, and the geometry was approximated as parallel rectangular plates, while the synovial fluid flow is modeled as a viscous, incompressible, and Newtonian fluid. The modified Reynolds equation is obtained using the principles of hydrodynamic lubrication and continuum mechanics, and it is solved using the appropriate boundary conditions. The expressions for pressure distribution, load-bearing capacity, and squeezing time are then determined, and theoretical analysis for various parameters is conducted. Pressure is increased by squeeze velocity and viscosity, while it is decreased by permeability and film thickness, leading to an unhealthy knee joint and a reduction in knee joint mobility. The load capacity of the knee joint decreases with permeability and increases with viscosity and squeezing velocity, resulting in a reduction in the load-carrying capacity of the knee joint in diseased conditions. Synovial knee joint illness is indicated by increased pressure and squeeze time. The squeeze film properties of synovial joints are important for maintaining joint health and function. Joint diseases such as osteoarthritis, rheumatoid arthritis, and gout can affect the composition and production of synovial fluid, leading to changes in squeeze film properties and potentially causing joint damage and pain. Understanding these relationships can help in the development of effective treatments for joint diseases.

Endogenous production of hyaluronan, PRG4, and cytokines is sensitive to cyclic loading in synoviocytes.

Synovial fluid is composed of hyaluronan and proteoglycan-4 (PRG4 or lubricin), which work synergistically to maintain joint lubrication. In diseases like osteoarthritis, hyaluronan and PRG4 concentrations can be altered, resulting in lowered synovial fluid viscosity, and pro-inflammatory cytokine concentrations within the synovial fluid increase. Synovial fibroblasts within the synovium are responsible for contributing to synovial fluid and can be targeted to improve endogenous production of hyaluronan and PRG4 and to alter the cytokine profile. We cyclically loaded SW982 synoviocytes to 0%, 5%, 10%, or 20% strain for three hours at 1 Hz. To assess the impact of substrate stiffness, we compared the 0% strain group to cells grown on tissue culture plastic. We measured the expression of hyaluronan turnover genes, hyaluronan localization within the cell layer, hyaluronan concentration, PRG4 concentration, and the cytokine profile within the media. Our results show that the addition of cyclic loading increased HAS3 expression, but not in a magnitude-dependent response. Hyaluronidase expression was impacted by strain magnitude, which is exemplified by the decrease in hyaluronan concentration due to cyclic loading. We also show that PRG4 concentration is increased at 5% strain, while higher strain magnitude decreases overall PRG4 concentration. Finally, 10% and 20% strain show a distinct, more pro-inflammatory cytokine profile when compared to the unloaded group. Multivariate analysis showed distinct separation between certain strain groups in being able to predict strain group, hyaluronan concentration, and PRG4 concentration from gene expression or cytokine concentration data, highlighting the complexity of the system. Overall, this study shows that cyclic loading can be used tool to modulate the endogenous production of hyaluronan, PRG4, and cytokines from synovial fibroblasts.

Significance of Brinkman and Stokes system conjuncture in human knee joint

Stokes’s equation in the fluid domain and Brinkman’s equation in the porous media are combined in the current study which is designated by the Stokes-Brinkman coupling. The current paper gives a theoretical analysis of the Stokes-Brinkman coupling. It has been shown that such a model is a good match for the knee joint. A flow model has been investigated in order to get a better understanding of the convective diffusion of the viscous flow along the articular surfaces between the joints. The Beavers and Joseph slip conditions which are a specific boundary condition for the synovial fluid are used to solve the governing system of partial differential equations for the synovial fluid and the results are provided here. We develop formulas for the interfacial velocity for both flow through special slip condition and analyse the link between the slip parameters alpha and beta . Thus, the damping force due to the porous medium naturally when we non-dimensionalize, some parameter which are controlling the structure like, beta and alpha . Through the development of an analytical solution and numerical simulation (using the finite volume approach) it is hoped that the mechanisms of nutritional transport into the synovial joint will be better understood. According to the data the average concentration has a negative connection with both the axial distance and the duration spent in the experiment. Many graphs have been utilized to gain understanding into the problem’s various characteristics including velocity and concentration, among others. Hyaluronate (HA) is considered to be present in porous cartilage surfaces and the viscosity of synovial fluid fluctuates in response to the amount of HA present.

Rheological and interface adhesive properties of osteoarthritic synovial fluids

Lubrication by synovial fluid is vital in maintaining the physiological operation of diarthrodial joints, which can be compromised due to changes in synovial fluid as osteoarthritis progresses, resulting in a lubrication deficiency. We studied the rheological and interface adhesive properties of osteoarthritic synovial fluid samples (49 in total), aiming to establish the correlation with medical conditions experienced by patients who underwent knee or hip Total Joint Replacement due to osteoarthritis. The steady-state rheology and the interfacial adhesion energy of those samples were examined, of which the results were compared across various patient characteristics. Seniority (60–79 years old) and obesity (Body Mass Index above 30) were identified as the dominant risk factors for the degeneration of synovial fluid and, thus, the potential development of osteoarthritis. At low shear rates where the interactions are more prominent than high shear rates, synovial fluid viscosity decreased by 58% with age and 38% with Body Mass Index, while the shear-thinning index increased by 40% and 7%, respectively. Additionally, synovial fluid interfacial adhesion properties deteriorate, as shown by the adhesion energy results. The adhesion energy, which is positively correlated to the coefficient of friction, increased by 172% with age and by 234% with Body Mass Index. The changes in both rheological and interface adhesion properties of synovial fluid samples support the relationship between the physico-chemical properties and the clinical observation. The AFM based surface adhesion method could be considered as a new approach to evaluate the tribological characteristics of natural synovial fluids as it requires small volume of samples.

The intra‐articular injection of adipose‐derived stem cells decreases pain and reduces inflammation in knee osteoarthritis, with or without the addition of platelet‐rich plasma also improves functionality

The increase of individuals with Osteoarthritis (OA) has generated an increase in public spending in the treatments, which are still not that effective. So, the purpose of this study was to analyze and compare four types of interventions: platelet-rich plasma (PRP), adipose-derived stem cells (ADSCs), ADSCs+PRP and the standard surgical video arthroscopy (All groups passed through standard arthroscopy before intervention). The evaluation was performed by applying the questionnaires Western Ontario McMaster Universities, Short Form Health Survey 36 and Visual Analog Pain Scale, also by analyzing the synovial fluid (inflammatory cytokines, enzymatic, colorimetric and viscosity analysis), this evaluation happened in two moments: before the surgical procedures and after 6months of the interventions and also was made a comparison to standard arthroscopy. The questionnaires results showed a greater improvement in the scores of the domains analyzed in the ADSCs+PRP group, followed by the ADSCs and PRP group. In the evaluation of inflammatory cytokines, there was a significant reduction in the cytokine IL-1b only in the ADSCs+PRP group (46%) and ADSCs (31%), of IL-6 in the ADSCs+PRP group (72%), of IL-8 in the ADSCs+PRP group (50%) and ADSCs (31%), and TNF in the ADSCs+PRP group (46%). There was also a significant increase in the amount of total proteins (79%) in the control group and polymorphonuclear cells (47%) in the ADSCs+PRP group. Taking all the results into account, we infer that therapies with ADSCs+PRP and only ADSCs are safe and effective over 6months for the improvement of pain, functional capacity and joint inflammation in volunteers with OA. It is also considered that the use of ADSCs+PRP, particularly, is a promising alternative to help manage this disease, due to the better results presented among the four propose interventions.

Thermal bio-convective transport in biological fluid using two viscosity models

This article models the diffusion process of heat and mass transfer in synovial fluid (SF) which is viscous non-Newtonian and is present in the articular cartilage of the synovial joint. The viscosity of SF is a function of the concentration of hyaluronan (HA) and shear rate. The physicochemical properties of HA and the use of antioxidants is the main motivation for considering Brownian motion and thermophoresis in the synovial liquid. The mathematical models for viscosity depending upon concentration and shear rate dependent are coupled with conservation governing equations. To explore the behavior of material parameters on the lubricant nature of the SF models governing laws are solved. The impacts of parameters on friction between joints are examined which helps to analyze the lubricant nature of SFs. Subsequently, it also noted that, in a quantitative sense, viscosity models (model-I and model-II) behave slightly differently under parametric variation. Brownian motion (BM) of particles for the case of the model-I is higher than that for the case of the model-II. The concentration field decreases by increasing the BM of particles. However, the concentration field increases when thermophoresis effects are increased. It is also found from the simulations that thermophoresis effects for the case of a model-II are stronger than those for the case of model-I. BM of particles is responsible for an increase in the temperature for the case of both models.

The Metabolic Process After Lubrication of Human Joint and Skin Surfaces

Purpose The topic of the presented paper concerns the human body and joint cartilage run-walk treatment implemented by the Electro-Magnetic (EM) and Acoustic Emission (AE) field. The thesis is proved here i.e. running in presence of a EM and AE field, increases dynamic viscosity of bio-lubricant liquids, thus increases energy burn, metabolism and finally it leads to the decrements of the body weight and hence it accelerates the slimming process. Material and Methods The research methods used in this paper include the following: EM field produced by a new Polish Apparatus MF-24, MT-3, Germany Magcell Arthro magneto electronic devices for the human body and joint cartilage treatment, Bone Dias Apparatus applied in AE therapy produced in Germany, ( Univ. Applied Science Giessen), Segmental Body Composition Analyzer Tanita MC 780MA, pedometer Garmin Ltd.2015.The author gained experience in Germany research institutes, and practical results were obtained after measurements and information from students and patients. Results The EM-therapy and AE results presented in this paper concern betterments during typical human cartilage diseases and causes of the effects of the slimming process gained before and after run-walk training. The run-walk training results presented in this paper concern the effects of the slimming process gained without and after electro-magnetic field therapy. Conclusions The main conclusions obtained in this paper are as follows: The run-walk training implemented by the electro-magnetic induction field and AE leads to the increments of the dynamic viscosity of synovial fluid and human sweat, changes the internal energy contained in the human body, muscle and cartilage, hence it accelerates the slimming process connected with the body weight decrements as well the betterments effects during the therapy.

A Novel Device for the Quantification of Synovial Fluid Viscosity Via Magnetic Deflection.

Changes in synovial fluid viscosity may be used to detect joint disease; however, methods to evaluate these changes at the point-of-care are currently rudimentary. Previously, we demonstrated that magnetic particle translation through static synovial fluid could serve as a surrogate marker of synovial fluid mechanics. In this work, we examine the magnetic deflection of a stream of particles flowing through a stream of synovial fluid and relate this deflection to changes in fluid mechanics. First, a flow device was designed, where a stream of magnetic particles flows along with synovial fluid. As the particle stream approaches and passes a fixed permanent magnet, the particle stream deflects. Conceptually, as the synovial fluid viscosity decreases, the deflection of the particle stream should increase due to a decreased drag force opposing the force magnetization. To assess this concept, particle deflection was first measured in Newtonian glycerol solutions of known varying viscosity under different flow conditions. Next, the device was used to test bovine synovial fluid viscosity, which had been progressively degraded using ultrasonication. A strong correlation was observed between the deflection of the magnetic particles and the viscosity of the glycerol solutions (R2 = 0.987) and the amount of ultrasonic degradation of synovial fluid (R2 = 0.7045). In the future, the principle of particle deflection may be used to design point-of-care quantification of synovial fluid mechanics, as the assessment does not require particles to be separated from the fluid for quantification and could be conducted under simple flow conditions.

Rapid Aggregation of Staphylococcus aureus in Synovial Fluid Is Influenced by Synovial Fluid Concentration, Viscosity, and Fluid Dynamics, with Evidence of Polymer Bridging.

ABSTRACTEarly bacterial survival in the postsurgical joint is still a mystery. Recently, synovial fluid-induced aggregation was proposed as a potential mechanism of bacterial protection upon entry into the joint. As synovial fluid is secreted back into the joint cavity following surgery, rapid fluctuations in synovial fluid concentrations, composition, and viscosity occur. These changes, along with fluid movement resulting from postoperative joint motion, modify the environment and potentially affect the kinetics of aggregate formation. Through this work, we sought to evaluate the influence of exposure time, synovial fluid concentration, viscosity, and fluid dynamics on aggregation. Furthermore, we aimed to elucidate the primary mechanism of aggregate formation by assessing the interaction of bacterial adhesins with the synovial fluid polymer fibrinogen. Following incubation under each simulated postoperative joint condition, the aggregates were imaged using confocal microscopy. Our analysis revealed the formation of two distinct aggregate phenotypes, depending on whether the incubation was conducted under static or dynamic conditions. Using a surface adhesin mutant, we have narrowed down the genetic determinants for synovial fluid aggregate formation and identified essential host polymers. We report here that synovial fluid-induced aggregation is influenced by various changes specific to the postsurgical joint environment. While we now have evidence that select synovial fluid polymers facilitate bridging aggregation through essential bacterial adhesins, we suspect that their utility is limited by the increasing viscosity under static conditions. Furthermore, dynamic fluid movement recovers the ability of the bacteria with surface proteins present to aggregate under high-viscosity conditions, yielding large, globular aggregates.

Analysis of factors influencing the qualitative characteristics of equine synovial fluid

The objective of the present study was to investigate the viscoelastic properties in synovial fluid between normal horses and horses with naturally occurring OA and to detect factors affecting synovial fluid viscosity. In total, 105 horses were included in this study. Synovial fluid samples were obtained from 60 mature horses with mild to moderate osteoarthritis in the 2nd interphalangeal, the metacarpophalangeal or the intercarpal joint. Forty-five horses were used as controls. Full rheological sample characterization was performed in order to measure the elastic G’ and viscous G’’ moduli. For determining hyaluronic acid concentrations a commercially available ELISA kit was used. The results of the linear mixed effect (LME) model revealed statistically significant (p < 0.001) effect of HA concentration, on the mean values of logG’ and logG” measurements. The ANOVA findings of the final model revealed statistically significant effect of joint type (p < 0.001) on the mean values of viscoelastic measurements. Interpreting the coefficients of the covariates osteoarthritis (p < 0.001) and age (p = 0.013), a negative correlation was detected on the response logG’ and logG” measurements. Geldings seemed to present lower viscous properties compared to mares. To the authors’ knowledge this is the first multivariate study to quantitatively evaluate the several factors that affect the viscoelastic properties of equine synovial fluid. Horses with osteoarthritis seemed to present lower viscoelastic properties compared to the healthy subjects that are joint type dependant. Finally, considering the multifactorial nature of osteoarthritis, one should expect an emerging need of personalized disease-modifying treatments.

Synovial Joint Study

The impact of certain separate characteristics, including the porosity parameter, reaction rate parameter, and viscoelastic parameters of steady convective diffusion across a rectangular channel, has been investigated in this article. The model’s momentum and concentration equations were developed using the similarities technique, and the numerically finite volume method was combined with the Beavers and Joseph slip conditions. Various graphs have been used to get insight into various parameters of the problem on velocity and concentration. The cartilage surfaces are assumed to be porous, and the viscosity of synovial fluid varies with hyaluronate (HA) content.

Effective stride length on load carrying capacity for ankle joint

In this paper, discussion load carrying capacity of person ankle joint in stance stage & swing stage and mathematical modeling approval on the Reynolds and continuity equation. Elastic deformation of non-Newtonian synovial fluid & speed phase is mathematically elicited. Theoretical explanation load carrying with several viscosity of synovial fluid, porosity and stride length in daily tasks we provided the elastic deformation that escorts the joint with diverse footing speed is the hardest factor determining walking pattern for both sexes.

Hyaluronic acid synthesis, degradation, and crosslinking in equine osteoarthritis: TNF-\u03b1-TSG-6-mediated HC-HA formation

BackgroundTNF-α-stimulated gene 6 (TSG-6) protein, a TNF-α-responsive hyaladherin, possesses enzymatic activity that can catalyze covalent crosslinks of the polysaccharide hyaluronic acid (HA) to another protein to form heavy chain-hyaluronic acid (HC-HA) complexes in pathological conditions such as osteoarthritis (OA). Here, we examined HA synthase and inflammatory gene expression; synovial fluid HA, TNF-α, and viscosity; and TSG-6-mediated HC-HA complex formation in an equine OA model. The objectives of this study were to (1) evaluate the TNF-α-TSG-6-HC-HA signaling pathway across multiple joint tissues, including synovial membrane, cartilage, and synovial fluid, and (2) determine the impact of OA on synovial fluid composition and biophysical properties.MethodsHA and inflammatory cytokine concentrations (TNF-α, IL-1β, CCL2, 3, 5, and 11) were analyzed in synovial fluid from 63 OA and 25 control joints, and HA synthase (HAS1-3), TSG-6, and hyaluronan-degrading enzyme (HYAL2, HEXA) gene expression was measured in synovial membrane and cartilage. HA molecular weight (MW) distributions were determined using agarose gel electrophoresis and solid-state nanopore measurements, and HC-HA complex formation was detected via immunoblotting and immunofluorescence. SEC-MALS was used to evaluate TSG-6-mediated HA crosslinking, and synovial fluid and HA solution viscosities were analyzed using multiple particle-tracking microrheology and microfluidic measurements, respectively.ResultsTNF-α concentrations were greater in OA synovial fluid, and TSG6 expression was upregulated in OA synovial membrane and cartilage. TSG-6-mediated HC-HA complex formation was greater in OA synovial fluid and tissues than controls, and HC-HA was localized to both synovial membrane and superficial zone chondrocytes in OA joints. SEC-MALS demonstrated macromolecular aggregation of low MW HA in the presence of TSG-6 and inter-α-inhibitor with concurrent increases in viscosity.ConclusionsSynovial fluid TNF-α concentrations, synovial membrane and cartilage TSG6 gene expression, and HC-HA complex formation were increased in equine OA. Despite the ability of TSG-6 to induce macromolecular aggregation of low MW HA with resultant increases in the viscosity of low MW HA solutions in vitro, HA concentration was the primary determinant of synovial fluid viscosity rather than HA MW or HC-HA crosslinking. The TNF-α-TSG-6-HC-HA pathway may represent a potential therapeutic target in OA.

Targeting joint inflammation for osteoarthritis management through stimulus-sensitive hyaluronic acid based intra-articular hydrogels

Numerous therapeutic strategies have been developed for osteoarthritis (OA) management, including intra-articular (IA) injections. The ideal IA formulation should control cartilage degradation and restore synovial fluid viscosity. To this end, we propose to combine thermo-sensitive polymers (poloxamers) with hyaluronic acid (HA) to develop suitable beta-lapachone (βLap) loaded IA formulations. The development of IA formulations with these components entails several difficulties: low βLap solubility, unknown βLap therapeutic dose and the bonded commitment of easy administration and viscosupplementation. An optimized formulation was designed using artificial intelligence tools based on the experimental results of a wide variety of hydrogels and its therapeutic capacity was evaluated on an ex vivo OA model. The formulation presented excellent rheological properties and significantly decreased the secretion of degradative (MMP13) and pro-inflammatory (CXCL8) molecules. Therefore, the developed formulation is a promising candidate for OA treatment restoring the synovial fluid rheological properties while decreasing inflammation and cartilage degradation.

Investigation of synovial fluid lubricants and inflammatory cytokines in the horse: a comparison of recombinant equine interleukin 1 beta-induced synovitis and joint lavage models

BackgroundLameness is a debilitating condition in equine athletes that leads to more performance limitation and loss of use than any other medical condition. There are a limited number of non-terminal experimental models that can be used to study early inflammatory and synovial fluid biophysical changes that occur in the equine joint. Here, we compare the well-established carpal IL-1β-induced synovitis model to a tarsal intra-articular lavage model, focusing on serial changes in synovial fluid inflammatory cytokines/chemokines and the synovial fluid lubricating molecules lubricin/proteoglycan 4 and hyaluronic acid. The objectives of this study were to evaluate clinical signs; synovial membrane and synovial fluid inflammation; and synovial fluid lubricants and biophysical properties in response to carpal IL-1β synovitis and tarsal intra-articular lavage.ResultsHyaluronic acid (HA) concentrations, especially high molecular weight HA, and synovial fluid viscosity decreased after both synovitis and lavage interventions. Synovial fluid lubricin concentrations increased 17–20-fold for both synovitis and lavage models, with similar changes in both affected and contralateral joints, suggesting that repeated arthrocentesis alone resulted in elevated synovial fluid lubricin concentrations. Synovitis resulted in a more severe inflammatory response based on clinical signs (temperature, heart rate, respiratory rate, lameness and joint effusion) and clinicopathological and biochemical parameters (white blood cell count, total protein, prostaglandin E2, sulfated glycosaminoglycans, tumor necrosis factor-α and CC chemokine ligands − 2, − 3, − 5 and − 11) as compared to lavage.ConclusionsSynovial fluid lubricin increased in response to IL-1β synovitis and joint lavage but also as a result of repeated arthrocentesis. Frequent repeated arthrocentesis is associated with inflammatory changes, including increased sulfated glycosaminoglycan concentrations and decreased hyaluronic acid concentrations. Synovitis results in more significant inflammatory changes than joint lavage. Our data suggests that synovial fluid lubricin, TNF-α, CCL2, CCL3, CCL5, CCL11 and sGAG may be useful biomarkers for synovitis and post-lavage joint inflammation. Caution should be exercised when performing repeated arthrocentesis clinically or in experimental studies due to the inflammatory response and loss of HA and synovial fluid viscosity.

Inflammatory and Noninflammatory Synovial Fluids Exhibit New and Distinct Tribological Endotypes.

Inferior synovial lubrication is a hallmark of osteoarthritis (OA), and synovial fluid (SF) lubrication and composition are variable among OA patients. Hyaluronic acid (HA) viscosupplementation is a widely used therapy for improving SF viscoelasticity and lubrication, but it is unclear how the effectiveness of HA viscosupplements varies with arthritic endotype. The objective of this study was to investigate the effects of the HA viscosupplement, Hymovis®, on the lubricating properties of diseased SF from patients with noninflammatory OA and inflammatory arthritis (IA). The composition (cytokine, HA, and lubricin concentrations) of the SF was measured as well as the mechanical properties (rheology, tribology) of the SF alone and in a 1:1 mixture with the HA viscosupplement. Using rotational rheometry, no difference in SF viscosity was detected between disease types, and the addition of HA significantly increased all fluids' viscosities. In noninflammatory OA SF, friction coefficients followed a typical Stribeck pattern, and their magnitude was decreased by the addition of HA. While some of the IA SF also showed typical Stribeck behavior, a subset showed more erratic behavior with highly variable and larger friction coefficients. Interestingly, this aberrant behavior was not eliminated by the addition of HA, and it was associated with low concentrations of lubricin. Aberrant SF exhibited significantly lower effective viscosities compared to noninflammatory OA and IA SF with typical tribological behavior. Collectively, these results suggest that different endotypes of arthritis exist with respect to lubrication, which may impact the effectiveness of HA viscosupplements in reducing friction.

Computational study on synovial fluid flow behaviour in cartilage contact gap under osteoarthritic condition

This study numerically investigates the pathological changes of fluid flow in cartilage contact gap due to the changes in cartilage surface roughness and synovial fluid characteristics in osteoarthritic (OA) condition. First, cartilage surface topographies in both healthy and OA conditions are constructed using a numerical approach with consideration of both vertical and horizontal roughness. Then, constitutive equations for synovial fluid viscosity are obtained through calibration against previous experimental data. Finally, the roughness and synovial fluid information are input into the gap flow model to predict the gap permeability. The results show that the rougher surface of OA cartilage tends to decrease gap permeability by around 30%–60%. More importantly, with the reduction in gap size, the decrease in gap permeability becomes more significant, which could result in an early fluid ultrafiltration into the tissue. Moreover, it is demonstrated that the pathological synovial fluid has more deleterious effects on the gap permeability than the OA cartilage surface, as it could potentially increase the gap permeability by a few hundred times for pressure gradients less than 106 Pa/m, which could inhibit the fluid ultrafiltration into the tissue. The outcomes from this research indicate that the change in fluid flow behaviour in contact gap in OA condition could significantly affect the function of articular joints.

A NEW CONTRIBUTION IN STOCHASTIC HYDRODYNAMIC LUBRICATION FOR ARBITRARY BIO-SURFACES

This paper shows a recent progress described in curvilinear, orthogonal coordinates of the method of estimation of stochastic bio-hydrodynamic lubrication parameters. Here are discussed real arbitrary movable, non-rotational living biological surfaces coated with phospholipid bi-layers and lubricated with biological liquids. Non-rotational, curvilinear cooperating biological surfaces take the place in various biological nods for example in sacra bone, femoral bone, knee cap, calf bone and hip joint, elbow joint, knee joint, jump joint. Moreover are assumed biological non-rotational friction nods between human skin and tightly sport dress lubricated with the sweat. The main focus of the paper was to demonstrate the influence of expected values variations and standard deviation of the human joint gap height on the hydrodynamic lubrication parameters occurring during the friction process. It is very important to notice that the random gap height variations imply on the apparent dynamic viscosity of biological fluid or synovial fluid.