CCN4 and rheumatoid arthritis: Whereas CCN4 is not expressed in normal hip synovium samples and is undetectable in normal hip, RA knee and RA hip cartilage obtained from patients undergoing joint replacement, weak-to-moderate CCN4 expression has been found in the superficial layers, matrix and perivascular cells of OA hip, RA knee and OA knee synovium samples from patients with advanced RA or OA disease [47].