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ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

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FRICTIONAL PROPERTIES OF OSTEOARTHRITIC CARTILAGE<br />

DURING 3D ANALYSIS<br />

1. ABSTRACT<br />

R. Aissaoui 1<br />

The objective of this study was to determine the difference in knee articular cartilage<br />

frictional properties during gait between osteoarthritic (OA) and healthy subjects. Gait<br />

analysis on treadmill was performed on twenty-five OA and fourteen healthy subjects.<br />

An inverse dynamics model and a reductionist contact model of the knee were used to<br />

estimate respectively the joint reactions forces and moments and tibiofemoral contact<br />

forces. The normal contact forces were inputted to a numerical biphasic poroviscoelastic<br />

model which represents knee articular cartilage in order to estimate its<br />

corresponding fluid pressure. Then the effective friction coefficient was derived using a<br />

friction model representative of the weeping mechanism of lubrication and the friction<br />

surface force was then estimated. The friction surface force was found to be<br />

significantly higher for OA subjects than for healthy subjects. The friction coefficient<br />

was found to have an important contribution to the differences in friction surface force<br />

between both cohorts during the stance phase whereas normal contact force was found<br />

to have a less important contribution<br />

2. INTRODUCTION<br />

Osteoarthritis (OA) is a degenerative disease affecting the mechanical and structural<br />

properties of articular cartilage. Though its etiology is not completely understood, it is<br />

quite accepted that joint mechanics affect considerably its progression [1, 2]. Andriacchi<br />

et al. [1] described the initiation and progression of osteoarthritis due to abnormal<br />

kinematics which changes the contact force location at the articular surfaces which lead<br />

to surface fibrillation. Fibrillation of articular surfaces increases surface roughness and<br />

therefore increases surface friction. An increase in surface friction lead to higher<br />

internal shear stresses which can possibly enhance matrix degradation. Also, since<br />

surface friction is proportional to the normal contact force applied on the articulation, it<br />

follows that a decrease in normal contact force could slow the progression of OA by<br />

decreasing the surface friction force.<br />

One of the main functions of articular cartilage is to ease joint motion during daily<br />

activities by providing good lubricating properties. Surface friction, which is due to the<br />

contribution of the surface roughness and the sheared-lubricant film, restrains joint<br />

motion. Though surface friction depends on surface roughness, it depends also on<br />

lubrication modes. Few theories have been developed in the past to describe the<br />

lubrication of articular surfaces in vivo but none of them can account for all<br />

physiological cases [3]. McCutchen [4] proposed the weeping mechanism which is a<br />

fluid-film lubrication theory based on interstitial fluid pressurisation. From that theory,<br />

Ateshian et al. [5] proposed a model to estimate a friction coefficient that represents the<br />

contribution of surface roughness and the efficiency of the lubrication process. Their<br />

1 Professor, Laboratory of Imaging & Orthopeadic Research, Centre de Recherche du CHUM, École de<br />

technologie supérieure, 1100 Rue Notre-Dame Ouest, Montréal (Québec), Canada H3C 1K3.

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