Joint effusion

When the joint becomes diseased or some systemic disease occurs, joint fluid increases to form joint effusion, which causes joint pain and discomfort. A small amount of joint fluid is normally stored in the knee joint to nourish joint cartilage, lubricate the joint, and reduce friction during joint movement. The synovial fluid is secreted by the synovium, and the joint fluid is continuously renewed as the joint moves. When the joint becomes diseased or some systemic disease occurs, joint fluid increases to form joint effusion, which causes joint pain and discomfort. When the synovial fluid exceeds 10 ml, the floater test is positive.