Synovial tissue is found in joints, tendon sheaths, and bursae and allows smooth motion. Synovial tissue is organized in a membranous structure called the synovium.

This chapter describes the gross anatomy, histology, and function of synovium, on which the joints, tendons, and bursae depend for motion and metabolism. Synovial fluid, which is produced by the synovium and functions as the conduit for the synovium’s complex role, will also be discussed.

Both inflammatory and noninflammatory conditions affect the synovium. The discussion of normal synovium and synovial fluid will lay the groundwork for understanding these conditions as well as synovial fluid collections, termed effusions, which occur in inflammatory and noninflammatory states. An understanding of normal synovium is also required to appreciate uncommon diseases, such as pigmented villonodular synovitis (PVNS) and synovial chondromatosis, that are unique to synovial tissue. The second half of this chapter focuses on the pathologic conditions that can affect the synovium.