A porohyperelastic lubrication model for articular cartilage in the natural synovial joint

Abstract

This work focuses on the proposed mechanisms for the lubrication of synovial joints and applies them to an idealised bearing geometry considering a porohyperelastic material (cartilage) rotating against a stationary rigid impermeable surface. The model captures the behaviour of all lubrication regimes including fluid film formation and boundary contact as the load capacity is increased, representing a major advancement in modelling cartilage mechanics. Transient responses in the fluid phase are shown to be faster than those in the solid phase with the former decaying over time as fluid is exuded from the material. The complex behaviour of fluid migrating to and from the lubricating film is captured which leads to a better understanding of the hydration and friction mechanisms observed.

Compliant-poroelastic lubrication in cartilage-on-cartilage line contacts

“…Since the fluid is free to move between the contacting bodies this pressure is constant across the boundary. The loading magnitudes and stress distributions are comparable to those found in steady-state cases for rotation against an impermeable wall [31].…”

“…The strain energy density is used to define the hyperelastic response of the solid deformation in which the stress-strain relationship for the material is obtained by the derivative of strain energy density with respect to strain [32]. This expands on the concept of linear poroelasticity established for cartilage like materials by Mow, et al [5], [6] toward finite deformations and compliant materials as implemented by Simon [18] and more recently by de Boer et al [31] with respect to rotating interfaces and lubrication.…”

“…Soft fluid-filled porous materials of this nature have been modelled by coupling the continuum mechanics that describe a compliant-poroelastic material with thin film theory to describe the lubricating boundary [29], [30]. Recently, this was expanded to include a Stribeck type analysis of a compliant-poroelastic (or porohyperelastic) material rotating against an impermeable surface to show that the lubrication modes (boundary, mixed and hydrodynamic) can be predicted at given operating conditions [31]. The present work performs a similar Stribeck type analysis on two contacting compliant-poroelastic layers.…”

Synovial Joints. Tribology, Regeneration, Regenerative Rehabilitation and Arthroplasty

“…In one of the latest works carried out with the participation of D. Dowson, the mode of pore-hyperelastic lubrication articular cartilage in natural synovial joints was considered. According to the authors, this model describes all modes, including synovial fluid lubrication and boundary lubrication that occurs with increasing load, which represents major progress in modeling the mechanics of articular cartilage [49].…”

Duncan Dowson and elastohydrodynamic lubrication at Leeds University

“…The understanding of boundary and mixed lubrication contacts became an important research area in Leeds. 73,74 In the later years, Professor Dowson worked with a number of scientists at Leeds to develop new numerical models for predicting porous and soft tribological systems such as in cartilage 75 and oral cavity. 76 Similar to the early work on EHL theory, lubrication models were still remaining the critical path to understand the complex tribological performance in those applications.…”