The Probable Explanation for the Low Friction of Natural Joints.
The surface of an articular cartilage, coated with phospholipid (PL) bilayers, plays an important role in its lubrication and movement. Intact (normal) and depleted surfaces of the joint were modelled and the pH influence on the surface interfacial energy, wettability and friction were investigated. In the experiments, the deterioration of the PL bilayer was controlled by its wettability and the applied friction. The surrounding fluid of an undamaged articular cartilage, the synovial fluid, has a pH value of approximately 7.4. Buffer solutions were formulated to represent the synovial fluid with various pH values. It was found that the surface interfacial energy was stabilised at its lowest values when the pH varied between 6.5 and 9.5. These results suggested that as the PL bilayers deteriorated, the hydration repulsion mechanism became less effective as friction increased. The decreased number of bilayers changed the wettability and lowered PL lubricant properties.
Tribochemistry Consulting, Salt Lake City, UT, 84117, USA. zpawlak@xmission.com.|Biotribology Laboratory, Department of Physiotherapy, University of Bydgoszcz, Unii Lubelskiej 4c, 85-059, Bydgoszcz, Poland. zpawlak@xmission.com.
Zenon
Z
Pawlak
Faculty of Mathematics, Physics and Technical Sciences, Kazimierz Wielki University, Chodkiewicza 30, 85-867, Bydgoszcz, Poland.|Technical University, Legska 20, 87-800, Włocławek, Poland.
Wieslaw
W
Urbaniak
Department of Physiotherapy, University of Bydgoszcz, Unii Lubelskiej 4c, 85-059, Bydgoszcz, Poland.
Magdalena
M
Hagner-Derengowska
Collegium Medicum in Bydgoszcz, Department of Rehabilitation, Nicolaus Copernicus University in Torun, Curie Sklodowskiej 9, 85-094, Bydgoszcz, Poland.
Wojciech
W
Hagner
D000818:Animals; D002358:Cartilage, Articular / Q000378:metabolism; D002417:Cattle; D017276:Friction; D006863:Hydrogen-Ion Concentration; D013582:Synovial Fluid / Q000378:metabolism*; D017155:Wettability
Articular cartilage surface; Friction and wettability; Interfacial energy; Lamellar-repulsive lubrication; Phospholipids bilayers