The Probable Explanation for the Low Friction of Natural Joints

• Published in: Cell biochemistry and biophysics Vol. 71; no. 3; pp. 1615 - 1621
• Main Authors: Pawlak, Zenon, Urbaniak, Wieslaw, Hagner-Derengowska, Magdalena, Hagner, Wojciech
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.04.2015; Springer Nature B.V
• Subjects: Animals; Biochemistry; Biological and Medical Physics; Biomedical and Life Sciences; Biophysics; Biotechnology; Cartilage, Articular - metabolism; Cattle; Cell Biology; Friction; Hydrogen-Ion Concentration; Life Sciences; Original Paper; Pharmacology/Toxicology; Synovial Fluid - metabolism; Wettability; Friction and wettability; Interfacial energy; Articular cartilage surface; Lamellar-repulsive lubrication; Phospholipids bilayers
• ISSN: 1085-9195; 1559-0283
• DOI: 10.1007/s12013-014-0384-8

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.