what is knee joint effusion
Definition. A swollen knee occurs when excess fluid accumulates in or around your knee joint. Your doctor might refer to this condition as an effusion (ih-FYU-zhen) in your knee joint.efinition. A swollen knee occurs when excess fluid accumulates in or around your knee joint. Your doctor might refer to this condition as an effusion (ih-FYU-zhen) in your knee joint.