Milestones in natural lubrication of synovial joints

For years, physical and mathematical modeling of tribological phenomena in natural human synovial joints has been a great challenge for researchers and scientists. This short review is aimed to summarize main findings on the lubrication modelling in human synovial joints through the years, starting from first insights, underlining the evolution of the proposed theories. The complexity of the natural human synovial joints, in which biological, fluid dynamic, and tribological phenomena take place, makes this research area fascinating for scientists coming from several investigation fields. This manuscript underlines the necessity of a deep scientific cooperation between researchers from different branches of the involved disciplines to achieve the complete knowledge of these tribo-systems by taking in to account different points of view.