CCN6 and rheumatoid arthritis: CCN6 expression is generally undetectable in hip and knee joint tissues from patients with advanced RA or OA, and is minimal in the multilayered synovial cells from RA and OA knees [47], although evidence of high WISP3/CCN6 expression in end-stage OA cartilage suggests that CCN6 has a role in cartilage homeostasis [42].