We had previously shown that the joints of the zebrafish jaw and fin have synovial properties and are susceptible to degenerative arthritis in the absence of the lubricin-encoding gene prg4b (Askary et al., 2016), similar to the arthritis of synovial joints seen in mice and humans lacking lubricin (Rhee et al., 2005; Alazami et al., 2006; Hill et al., 2014; Koyama et al., 2014). The gene discussed is PRG4; the disease is arthritic joint disease.