Many people notice swelling in their knee and are told that “there’s water on the knee.” But what causes it? In this FAQ, a board-certified orthopedic specialist explains the causes, symptoms, and treatments of knee effusion in simple terms.

What does “water on the knee” mean?

“Water on the knee” refers to excess fluid buildup in or around the knee joint. The medical term for this condition is knee effusion. It can cause swelling, stiffness, and pain.

What causes fluid to build up in the knee?

Common causes include knee osteoarthritis, injury (like ligament or meniscus tears), gout, rheumatoid arthritis, or infection. Inflammation triggers fluid production in the joint.

What are the symptoms of knee effusion?

Symptoms include visible swelling, stiffness, heaviness, and pain when moving or bearing weight. In some cases, the knee may feel warm or look red due to inflammation.

How is the cause of knee effusion diagnosed?

Doctors perform a physical exam and may order X-rays, MRI, or joint fluid analysis to find the underlying cause, such as arthritis, injury, or infection.

Can water on the knee go away on its own?

Mild cases may improve with rest, ice, and elevation. However, persistent or recurring swelling requires proper diagnosis and treatment to prevent joint damage.

What treatments are available for knee effusion?

Treatment depends on the cause and may include anti-inflammatory medication, joint aspiration, physical therapy, or injections like PRP or corticosteroids.

When should I see a doctor for a swollen knee?

You should see a doctor if the swelling lasts more than a few days, causes significant pain, limits movement, or is accompanied by fever or redness.

We hope this FAQ helps you understand why fluid may accumulate in the knee and how to respond. If your symptoms continue, please consult a specialist for appropriate care.

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