Immunofluorescence staining of synovium showed more blood micro-vessels in OA patients and elevated IL6 and IL1B expression levels, suggesting that synovial inflammation might partly originate from pro-inflammatory cytokines in blood.<h4>Discussion</h4>These findings offered new understanding of the molecular mechanisms underlying blood and synovium communication in OA, and provided potential therapeutic drug targets for OA treatment to simultaneously modulate systemic inflammation and local angiogenesis. Here, IL6 is linked to inflammatory response.