Symptoms of knee effusion mainly include joint swelling, pain, and limitation of knee joint movement. 1. Joint swelling: joint swelling is the main clinical symptom, fluid accumulation is relatively small, generally swelling is not obvious. If there is more fluid, there will be obvious swelling of the knee joint. 2. Pain: Due to different causes, the pain caused by knee effusion is also different. The pain from synovitis is usually not obvious, and usually worsens with activity. The pain of effusion caused by ligament or meniscus injury is usually more obvious. 3. Restriction of knee joint activities: With a small amount of effusion, knee joint activities are generally not restricted. If the amount of fluid is large, the knee activities will be obviously limited, such as not being able to do squatting. If you have an effusion in your knee, you should seek medical attention and treatment promptly.