What Is Knee Joint Effusion?

When you suffer from a condition known as knee joint effusion, a certain amount of excess fluid has collected around or even within the joint of your knee. Often referred to as "water on the knee," the effusion is more so a complication of another condition. Most of the time, the fluid is synovial in nature, meaning that it comes directly from the joint itself, but you also may find that the fluid consists of something else, such as blood or even bacteria.

Is This an Emergency?

If you are experiencing serious medical symptoms, seek emergency treatment immediately.


The most common symptom of knee joint effusion is that of pain or discomfort, but you also may experience some swelling, stiffness and even bruising, depending on the cause of the excess fluid.


In most cases of water on the knee, the fluid accumulation is a result of an injury, such as a broken bone or torn ligament within the leg. This can occur during a fall or direct blow as well as from repetitive stress or overuse of the knee, like with any sport that involves a great deal of running or impact on the knees. But injury alone isn't the only cause of this condition. Osteoarthritis and rheumatoid arthritis are other common diseases that tend to cause effusion. Even conditions like gout or the formation of tumors and cysts can trigger the retention of fluid in and around your knee.


Although the complications of knee joint effusion are minimal, there is the potential for problems, especially when the condition is left unchecked. Besides hindering your overall mobility, you also can experience deterioration of the joint when the cause of the effusion is an infection, so make sure to seek medical advice.


Most treatments for knee joint effusion are based on the cause of the condition, making a "standard" approach to care nonexistent. However, many people with water on the knee need to have the excess fluid removed, so you may undergo a procedure known as aspiration. Other than that, you may need a series of corticosteroid injections, non-steroidal anti-inflammatory drugs (NSAIDs) or antibiotics to reduce inflammation or treat an infection. For others, knee surgery or even joint replacement may be necessary.


Along with any sort of medical care, knee joint effusion responds well to simple self-care measures, such as rest and elevation as well as icing and exercise. As with any sort of injury, ice should be applied to the affected area only for 15 to 20 minutes at a time. With exercise, a series of fitness activities are established by a physical therapist to strengthen the area to support the weakened knee.