The friction, lubrication, and adsorption at articular cartilage is a complex phenomenon of a heterogeneous supramolecular chemistry, mechanical loading, diversity, ageing, and a materials-energy balance for preventing cartilage-cartilage adhesion [44–46]. The lubricin is a mucinous glycoprotein initially known as superficial zone protein, a product of the superficial zone chondrocytes, biomechanically diffused in synovial joints to form a nano coating over the cartilage surface, prevent cartilage adhesion, and providing boundary lubrication or act as boundary lubricant [47]. The high molar mass hyaluronan (HA) presence in this synovial fluid provides viscosity for quasi-mechanical loading or impact resistance and protect cartilage in daily life [48]. The in-situ presence of phospholipids in synovial ingredients is due to the evolution of hydrophilic–hydrophobic macrostructure for a given phospholipid bilayer so it leads to a lamellar-repulsive mechanism in stable low-friction conditions [49]. The synovial fluid viscosity decreased by 58% with age and 38% with body mass index, the shear-thinning index increased by 40% and 7%, respectively as adhesion energy correlation to the coefficient of friction increased by 172% with age and by 234% with body mass index, and the interface adhesion properties of synovial fluid support the relationship with physicochemical properties [50]. The surface active hyaluronan molecules with phosphatidylcholine lipids present in joints to form a boundary lubricating layer create a tribology in providing the lubrication of synovial joints from the hydration lubrication [51]. The biotribology from friction, lubrication, and adsorption at articular cartilage is influenced by synovial fluid digestion or degradation due to lean mechanical work in anticipation of human body as a thermodynamic heat engine (Table 2) for effective materials and energy balance.
Table 2
The joint tribology of synovial fluid due to the heterogeneity of Lubricin/HA/Phospholipid, mechanical factors, aging, diversity of biology, and improper life style in assessment of moderate risk domain expressed by virtual survey of enlisted references for advancement of sustainable pattern of life [44–51]
Synergy | Factors |
Lubricin (230–280 kDa), Sperficial zone protein or SZP (345 kDa), hyalunoric acid or HA (3–7 MDa), and phospholipid biochemical environment of cartilage interface in providing ultra-low friction | Biochemistry |
Human locomotion evolves mechanical stress in a domain of boundary lubrication, mixed lubrication, and hydrodynamic lubrication regimes as a function of state variables | Mechanical stress |
Degradation of surface topography and lowering surface tension of tribological contacts for lean biological lubrication | Aging |
Diversity may be a little factor as Gender serving in a culture restricting mechanical work per day for assessment of risk tribological domain | Diversity |
Building up of body mass index due to lean mechanical work, lower net mechanical efficiency, and polluted environment influencing fuel oxidation | Work-life imbalance |
Metals, esters, ceramics, and synthetic polymers are used in biomedical surgery of articulating joints such as CoCrMo, titanium alloys, ultra-high weight polyethylene (UHMWPE), PLGA, and hydroxyapatite porous ceramics | Biomaterials |
A kinetic friction coefficient is being invariant with state variables to implement articular cartilage-on-cartilage lubrication test for validation of the friction properties on sliding velocity, axial load, and time, and establish conditions on boundary lubrication [52]. Titanium alloys and CoCrMo alloys used for hip and knee endoprostheses due to thermomechanical and physicochemical integrity for further studies of biofilm formation during aseptic and septic loosening [53–54]. Ultra-High Molecular Weight Polyethylene (UHMWPE) is used for tribological performance to provide durable implants in biomedical applications due to biocompatibility, ductility, and high wear resistance preferred in recent decades [55]. The definition of the biodegradable and bioabsorbable are used in the tissue engineering to discuss the rationale function as well as physicochemical properties of polymer scaffolds [56]. The biodegradable polymers useful for orthopedic biomaterials applications have secured the history for last five decades based on poly(lactides) and poly(glycolides) such as poly lactic acid (PLA) or poly lactic-co-glycolic acid (PLGA) among the most attractive polymers [57]. The biomaterials have been advanced decade to decades through three different generations, first generation for bioinert materials, second generation for biodegradable materials, and third generation for materials designed to stimulate responses at the molecular level based on metals, ceramics and polymers preferred in orthopaedic applications [58]. The topography and chemistry of bioimplant surfaces help in understanding the biological interactions or develop novel implant nano surface for biological interactive properties to regeneration of tissues, osteoblast functions, and bone scientific role in orthopaedic implants [59–60]. Bioengineering aims to restore biological functions to retain or modify damaged tissues in terms of key variables viz. Economy, Biocompatibility, and Mechanical properties.