Investigation of the rheological and tribological characteristics of human synovial fluid

The rising prevalence of knee arthrosis, driven by aging populations and modern lifestyles, has increased the demand for reliable orthopaedic implants. Metal alloys remain the most widely used implant materials, but their stability and performance are influenced by interactions with biological substances. The present study evaluates the rheological and tribological characteristics of human synovial fluid acquired from different age groups and genders with the future aim of developing a synthetic laboratory-produced lubricant that mimics the characteristics of synovial fluid and other surgical field materials. Rheological and tribological tests were performed on a rheometer to analyse viscosity, flow behaviour, and coefficient of friction. Fourier-transform infrared spectroscopy with Attenuated total reflectance (FTIR-ATR) spectroscopy was applied to evaluate the chemical composition of different biological samples. The study revealed that osteoarthritic synovial fluid viscosity was higher in male patients compared to females, while bovine-derived and artificial synovial fluid exhibited significantly higher viscosities than water-based solutions, which demonstrated the lowest viscosity. The tribological measurements revealed no significant difference in the coefficient of friction between samples from the young individual and the patients, whereas artificial synovial fluid and bovine synovial fluid demonstrated slightly higher coefficients of friction compared to the other samples. The findings provide key insights into the consistency and lubricity of human biological fluids and demonstrate the potential of synthetic lubricants for implant stability testing.