Water on the knee is one of those maladies that is just what it sounds like--excess fluid that accumulates in or around your knee joint. The fluid that builds varies depending upon the underlying cause or condition.
When your knee is damaged, it can cause the build-up of excess joint fluid. The damage can be caused by injury such as broken bones or ligament tears, or another disease or condition, such as infection, gout or arthritis.
Strenuous use of your knees, as with sports such as football or tennis, can put you at risk for developing water on the knee. Being overweight is also a risk factor.
Symptoms vary depending upon the original cause of the injury, but the most common signs are pain, swelling and stiffness.
Your doctor will examine your knee and will ask questions to determine how you've developed the condition. Additional diagnostic tests may be performed, such as X-rays, MRI or blood tests.
Your doctor can drain excess fluid from the joint, but full treatment requires addressing the underlying cause. Corticosteroid shots to reduce inflammation and antibiotics for infection are common. Surgery may also be an option.