septic arthritis, an acute form of arthritis characterized by bacterial inflammation of a joint caused by the spread of bacteria through the bloodstream from an infection elsewhere in the body or by contamination of a joint during trauma or surgery. The joint is stiff, painful, tender, warm, and swollen. The diagnosis is confirmed by bacteriological identification of an organism in a specimen obtained by aspiration of the joint. Parenteral antibiotics are given to prevent destruction of the joint and are continued for several weeks after inflammation has resolved. Repeated aspiration of the joint or surgical incision and drainage may be performed to relieve pressure on it. Physical therapy as the joint heals is helpful to restore it to full range of motion. Also called acute bacterial arthritis.