 The intimal lining of a synovial joint consists of unique cells called fibroblast-like synoviocytes FLS cells with interspersed macrophage-like synoviocytes. In the healthy joint macrophage-like synoviocytes are implicated in the innate immune defence and support adaptive immunity, while FLS cells function to regulate the release of nutrients and molecules, including hyaluronan, into the joint cavity. 