SARS-CoV-2 in the knee joint: a cadaver study.

Despite the considerable research efforts being made to learn more about COVID-19, little is known about the presence of SARS-CoV-2 genetic material in biological fluids other than respiratory droplets, blood, and feces. The aim of this post-mortem study was to assess the presence of SARS-CoV-2 RNA in the knee synovial fluid, synovial tissue, and bone tissue of COVID-19 patients in order to discover whether the joint is a possible route of transmission during orthopaedic surgical procedures, and clarify the possible role of SARS-CoV-2 as a directly arthritogenic virus. Post-mortem synovial fluid, synovial tissue and bone tissue samples were collected from the knees of five patients who died of COVID-19 in our hospital between September and October 2020, and analysed for the presence of SARS-CoV-2 using a commercial real-time polymerase chain reaction (RT-PCR) panel. Quantitative RT-PCR was used to test post-mortem nasopharyngeal swabs of all of the patients. No SARS-CoV-2 RNA was detected in any of the knee samples, despite the positivity of the throat swab. Our findings indicate that SARS-CoV-2 was not detected in knee synovial fluid, synovial membrane or bone. This makes it unlikely that these are potential sources of contagion, and suggests that SARS-CoV-2 is not directly arthritogenic.