The accumulation of fluid within a joint, such as the knee joint. Joint effusion may be caused by trauma, infection, gout, or arthritis. The resulting swelling may cause pain and restricted movement in the affected area. The escaped fluid is usually reabsorbed by the body within 1 t o 2 weeks, after which the symptoms of joint effusion improve. Sometimes, withdrawing the fluid with a fine needle (aspiration) is necessary for analysis or to help relieve pressure.
Increased fluid within a joint cavity. There may be increased production of synovial fluid following trauma, with some arthritic disease processes, or blood accumulating in the joint following trauma or surgery or due to hemophilia. Excessive amounts of synovial fluid, pus, or blood accumulate in many arthritic diseases (such as gout or rheumatoid arthritis), after trauma, in joint infections, following joint surgery, or in hemophilia.
Swelling, restricted movement, and often pain and tenderness can result from the accumulation of fluid in the area surrounding a joint. Each joint is enveloped by a capsule with a lining known as the synovium. The synovium typically generates a minimal quantity of lubricating fluid, called synovial fluid. Nonetheless, if the synovium suffers damage or inflammation (such as in the case of arthritis), it leads to the overproduction of this fluid.
Pain and inflammation can typically be eased with the use of painkillers, nonsteroidal anti-inflammatory drugs, and injections of corticosteroid drugs. The swelling often diminishes if the impacted joint is given rest, securely bandaged, cooled with ice packs, and kept raised. In certain instances, a needle and syringe may be used to extract the excess fluid from the joint.