Synovial fluid (SF), or synovia as Paracelsus denominated the egg white-like sticky intraarticular fluid, is a highly viscous fluid that lines all surfaces of the joint cavity with a thin film. Synovium is the thin tissue lining the internal side of the fibrous capsule. Cellular components in the SF are influenced by gravitational forces and sediment into the more steep parts of a joint at rest, as well as to the bottom of the tube after sampling. The samples of SF should preferably be directly transmitted into blood culture bottles filled with medium for optimal diagnostic yield of bacterial growth. The synovial fluid is mainly an ultrafi Urate of plasma with the addition of locally synthesized hyaluronan. The bone separating the cartilage from the underlying bone medulla is impermeable to nutrients.