The role of synovial fluid filtration by cartilage in lubrication of synovial joints—IV. Squeeze-film lubrication: The central film thickness for normal and inflammatory synovial fluids for axial symmetry under high loading conditions

Ultra-thin gas squeeze film characteristics are analyzed by extending Pan’s asymptotic theory for infinite squeeze number to the molecular gas film lubrication equation which was derived from the linearized Boltzmann equation and is valid for arbitrary Knudsen numbers. The generalized asymptotic method is shown to solve the boundary value equation which contains the flow rate coefficient as a function of the product of pressure P and film thickness H. Numerical results are obtained for a circular squeeze film. The PH ratio and the load carrying capacity ratio to those of continuum flow both decrease when the average film thickness is less than several microns because of molecular gas effects.

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Asperity Lubrication in Human Joints

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1243/pime_proc_1993_207_303_02 ◽

1993 ◽

Vol 207 (4) ◽

pp. 245-254 ◽

Cited By ~ 10

Author(s):

J Q Yao ◽

A Unsworth

Keyword(s):

Synovial Fluid ◽

Static Loading ◽

Fluid Film ◽

Loading Conditions ◽

Lubrication Mechanism ◽

Physiological Loading ◽

Human Joints ◽

Dynamic Loading Conditions ◽

Film Lubrication ◽

Fluid Film Lubrication

The asperity lubrication in human joints is examined in the present paper, with particular reference to the tertiary undulation with wavelengths of around 20–45 μm. It was found that, under dynamic physiological loading conditions, the secondary waviness of the cartilaginous surface (typically 0.5 mm wavelength) could be effectively flattened to sustain a fluid film of 0.1–0.3 μm thick, while the tertiary waviness could be squashed to sustain a much thinner fluid film of 0.01 μm (10 nm) thick with normal synovial fluid as the lubricant. The calculated film thickness for the tertiary undulation was less than 5 nm when the ankle joint was lubricated by Ringer's solution or pathological synovial fluids, or when only quasi-static loading conditions were considered, while a sufficiently thick fluid film could still be formed when the secondary undulations were considered alone. It was thus suggested that the fluid film lubrication mechanism was operative for human joints with normal synovial fluid as the lubricant under physiological dynamic loading conditions and the mixed lubrication mechanism could take over when static loading conditions prevailed or when watery lubricants (n ≈ 0.001 Pas) were used.

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A Mechanism to Explain Physiological Lubrication

Journal of Biomechanical Engineering ◽

10.1115/1.4001422 ◽

2010 ◽

Vol 132 (7) ◽

Cited By ~ 5

Author(s):

David F. James ◽

Garret M. Fick ◽

W. Douglas Baines

Keyword(s):

Hyaluronic Acid ◽

Synovial Fluid ◽

Articular Surface ◽

Constant Load ◽

Squeeze Film ◽

Hydrodynamic Resistance ◽

Low Viscosity ◽

Electrostatic Charges ◽

Articular Surfaces

A new mechanism of physiological lubrication is proposed to explain how low-viscosity synovial fluid prevents articular surfaces from contacting and wearing. The new mechanism is based on the hypothesis that the hyaluronic acid chains in synovial fluid bind to the cartilage surfaces through electrostatic charges, with the phospholipid layer on an articular surface supplying the necessary attractive charges. The stationary hyaluronic acid network causes a large hydrodynamic resistance to outward flow from the gap. To determine the effectiveness of the network in preventing contact, squeeze-film flow between two incompressible, permeable disks is analyzed when a constant load is suddenly applied, and the solvent—synovial fluid minus the hyaluronic acid—escapes through the network and through the permeable disks. The analysis yields the approximate time for the gap distance to decrease to asperity size. For realistic physiological parameters, the time for the surfaces to contact is a minimum of several minutes and likely much longer. The role of albumin in the synovial fluid is included because the large protein molecules are trapped by the small openings in the hyaluronic acid network, which increases the flow resistance of the network and thereby delays contact of the surfaces.

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Particularities of the Pseudo-Plastic Lubrication, with Application to the Sinovial Liquid

Proceedings of the 8th International Scientific Conference "BALTTRIB 2015" ◽

10.15544/balttrib.2015.06 ◽

2015 ◽

Author(s):

I. Radulescu ◽

A.V. Radulescu ◽

J. Javorova

Keyword(s):

Friction Coefficient ◽

Synovial Fluid ◽

Film Thickness ◽

Pressure Distribution ◽

Power Law ◽

Hip Joint ◽

Load Capacity ◽

Squeeze Film ◽

Power Law Model ◽

Spherical Surfaces

The present paper proposes a new model for lubrication of the hip joint with hyaluronan solutions, considering the squeeze film process of non-Newtonian fluid between rigid spherical surfaces. The heological model that approximately describes the behaviour of the synovial fluid is the power law model. For the considered case, the pressure distribution, the load capacity, the film thickness and the friction coefficient have been determinated. The conclusions of the paper offer an explication to the development of the osteoarthritis and to the problems of the arthritic patients.

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Squeeze Film Lubrication for Articular Cartilage with Synovial Fluid

Biomechanics of Diarthrodial Joints ◽

10.1007/978-1-4612-3450-0_14 ◽

1990 ◽

pp. 347-367 ◽

Cited By ~ 3

Author(s):

J. S. Hou ◽

M. H. Holmes ◽

W. M. Lai ◽

V. C. Mow

Keyword(s):

Articular Cartilage ◽

Synovial Fluid ◽

Squeeze Film ◽

Film Lubrication

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Normal Approach of a Cylinder towards an Elastic Layer

Journal of Mechanical Engineering Science ◽

10.1243/jmes_jour_1980_022_017_02 ◽

1980 ◽

Vol 22 (2) ◽

pp. 65-70 ◽

Cited By ~ 6

Author(s):

C. J. Cudworth ◽

J. F. Mykura

Keyword(s):

Film Thickness ◽

Elastic Layer ◽

Squeeze Film ◽

Pressure Curve ◽

Rigid Surface ◽

Dry Contact ◽

Dry Conditions ◽

Thin Elastic Layer ◽

Pressure Boundary Conditions ◽

Film Lubrication

This paper considers the squeeze film lubrication process of a cylinder approaching a plane rigid surface covered in a thin elastic layer. A simplified lubrication theory is presented, which makes the assumption that the shapes of the solids are the same as the elastically deformed surfaces under dry conditions. The lubrication equations are solved using alternative pressure boundary conditions derived from the dry contact pressure curve. In the experiments, lubricant film thickness is measured using optical interference methods. Curves of film thickness against time are plotted, and the effects on these curves of variations in load and layer thickness are shown to agree with the predictions of the theory.

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