Fu J, et al. - In this prospective study, authors examined 45 candidates undergoing revision for periprosthetic joint infection (PJI) (n=15), revision for aseptic failure (n=15), and primary arthroplasty (n=15) to examine the sensitivity and specificity of synovial fluid viscosity in the diagnosis of PJI using the Musculoskeletal Infection Society criteria. In patients with PJI, they recorded a significantly lower level of synovial fluid viscosity (7.93 mPa·s, range 3.0-15.0) vs those with aseptic failure (13.11 mPa·s, range 6.3-20.4). They determined 11.80 mPa·s as the optimal threshold value for synovial fluid viscosity for diagnosing PJI using Youden’s index. They found that synovial fluid viscosity exceeded C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and plasma d-dimer as a marker, with a sensitivity of 93.33% and a specificity of 66.67%, so they recommended synovial fluid viscosity as a promising marker for diagnosing PJI.