What Is Fluid on the Knee?

Fluid on the knee, or water on the knee, is a condition involving an excessive amount of fluid accumulating inside the knee joint or around it. The fluid builds up due to an injury or an underlying medical condition.

Symptoms

• According to the Mayo Clinic, water on the knee can cause swelling, bruising or stiffness around the knee. Patients may experience pain when putting weight on an affected knee.

Testing

• Laboratory tests may be done on a patient's blood or on joint fluid that has been removed from the knee to determine the cause of excessive fluid accumulation. To identify bone and joint abnormalities, X-rays or magnetic resonance imaging (MRI) may be used to identify bone and joint abnormalities.

Causes

• Excess synovial joint fluid can build up due to broken bones or injuries to ligaments and tendons. Osteoarthritis, rheumatoid arthritis and infections may cause excess knee fluid.

Risk Factors

• People who participate in sports that involve rapid knee movements (such as football or tennis) have an increased risk of developing water on the knee. Overweight people have a higher risk of developing excessive knee fluid because more pressure is placed on their knee joints when they walk.

Treatments

• Water on the knee may be treated with a joint fluid aspiration procedure that removes the fluid. Antibiotics may be prescribed to fight infection in the joint fluid.