Joint Effusion (Swollen Joint)

If your knee looks larger than usual, you might have joint effusion (a swollen joint). Joint effusion can be a sign of an injury, a type of arthritis or another condition. There are treatments you can try at home in addition to ones prescribed by your healthcare provider.


Medical illustration showing a swollen joint affecting an athlete along with an illustration of joint effusion happening on the inside of a knee.
A swollen synovial bursa inside a knee joint

What is joint effusion?

Joint effusion (a swollen joint) happens when extra fluids flood the tissues around your joint. The fluids make your joint look larger and puffier compared to your other joints. Your bones form joints when two or more of them connect. Your knee, for example, is made up of three bones:

  • The femur (thigh bone).
  • The tibia (shin bone).
  • The patella (kneecap).

But your joints also consist of tissues that have various purposes:

  • Bursas. These sacks of fluid act like protective cushions between your bones, ligaments and other parts of your joints.
  • Cartilage. Cartilage covers each bone where it connects at your joints. This slick tissue protects your knee by keeping your bones from rubbing directly together.
  • Ligaments. The elastic band-like ligaments connect your bones and support your joints.
  • Synovial membrane. This important tissue lubricates your joints with a sticky liquid called synovial fluid.
  • Tendons. Tendons connect bones and muscles. They control how your joints move.

All of these bones and tissues work together to help your joints function — to help them bend, flex, straighten, rotate and bear your weight. Joint effusion is when fluids enter one or more of these tissues.

Joint effusion can affect your knee and other big joints. Examples include your:

  • Ankle.
  • Elbow.
  • Shoulder.

Joint effusion can also affect your small joints, such as your:

  • Finger.
  • Toe.
  • Wrist.

Ordinarily, there is a little bit of fluid already in the joint tissues. The fluid can consist of several substances, including:

  • Blood.
  • Fat.
  • Proteins.
  • Synovial fluid.

But, if there are more fluids than usual in your joint, you have effusion (a swollen knee joint). Other symptoms that often go along with a swollen joint include:

  • Aching pain.
  • Difficulty moving the joint.
  • Fever.
  • Heaviness in the joint.
  • Redness.
  • Stiffness.
  • Warm skin.

These are symptoms of various diseases and conditions.


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Possible Causes

What are the most common causes of joint effusion (swollen joint)?

There are several reasons why your knee or other joints might swell with fluid. The most common reasons include:

  • Infection. An infection in your joint is called septic arthritis. Septic arthritis is a serious disease that can damage or even destroy your joint. You might need a joint replacement — a type of surgery — because of it. When you have an infection, your joint tissues can fill with pus. Pus is a protein-rich liquid that’s full of dead white blood cells.
  • Inflammation. This may be from conditions such as arthritis — especially osteoarthritisgout or rheumatoid arthritis.
  • Overuse. This is when you use a joint too much. For example, running too hard and often might cause your knee to swell.
  • Trauma. A ligament injury or a broken bone (bone fracture) are examples of trauma that can lead to swelling. Possible causes of such injuries include contact sports and car accidents.
  • Tumor. A mass of tissue that might be benign (noncancerous) or cancerous.

Care and Treatment

How is joint effusion (swollen joint) treated?

The cause of your knee joint effusion determines its care and treatment. Often once the cause of the swollen joint gets treated, the swelling goes away. However, not all causes of a knee joint effusion are curable. For many, treatment consists of managing your symptoms instead of eliminating them. There are several ways healthcare providers manage your swollen joint. Examples include:

  • Antibiotics help with infections. If you have septic arthritis — an infection in your knee joint — your healthcare provider might prescribe antibiotics.
  • Arthrocentesis is where your healthcare provider drains the synovial fluid from your swollen joint. They might send it to a lab for testing. Tests could reveal bacteria, proteins, certain blood cells, glucose or other indications of various conditions.
  • Colchicine is a medication for people who have gout. It helps with pain, inflammation and joint effusion.
  • Steroids help block inflammatory chemicals. Arthritis can cause inflammation, and inflammation can cause joint effusion. Some steroids get swallowed, and others are injected right into your knee joint.

Contact your healthcare provider when you need treatment for a swollen joint. They can help you figure out the best treatment for your joint effusion.


What can I do at home to treat joint effusion?

If your joint swells from fluid, there are a few steps you can take yourself. At-home remedies for joint effusion include:

  • Heat, especially moist heat, can help with joint effusion and joint pain. People who have arthritis or a swollen joint because of an injury might want to try heat.
  • Ice works well on swollen joints. Try it if you have arthritis or an injury.
  • Maintaining a healthy weight to reduce stress on your joints.
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil®, Motrin®) and naproxen (Aleve®). NSAIDs help treat the swollen joint of people who are injured or have arthritis.
  • Resting your joint effusion might help it heal. Try taking weight off your joint by raising it and use a mobility aid like a cane.

When To Call the Doctor

When should joint effusion (swollen joint) be treated by a healthcare provider?

You should contact emergency services or go to the emergency department if you have the following symptoms:

  • A broken bone or torn ligament.
  • A joint effusion with a fever.
  • An inability to move your joint.
  • An inability to put weight on your joint.
  • Loss of feeling in your joint.

Joint effusion plus a fever might mean that you have an infection in your joint (septic arthritis). Septic arthritis can seriously damage your joint. You might even need surgery. See a healthcare provider right away to prevent permanent damage. There are treatments to help you recover from septic arthritis.

Contact your healthcare provider if you have symptoms of arthritis. Although different types of arthritis have different symptoms, there are some common symptoms that include:

  • Pain in your joint.
  • Redness on the skin around your joint.
  • Stiffness in your joint.
  • Skin tenderness around the joint.
  • Swelling around your joint (joint effusion).
  • Warm skin around the joint.

Additional Common Questions

Is joint effusion painful?

Pain sometimes goes along with a joint effusion (swollen joint). You might feel a slight tenderness or a deep ache. Talk to your healthcare provider about what you can do to relieve both the pain and swelling.

How long does joint effusion take to heal?

How long joint effusion takes to heal depends on what caused it. If one of the bones that makes up the joint breaks, you might have joint effusion for weeks or months. If you have joint effusion because of osteoarthritis, you might deal with swollen joints for your lifetime. There are treatments, though, that can lessen the severity of your symptoms. They don’t have to interrupt your daily life.

Does joint effusion go away?

Check with your healthcare provider. They can determine if you need treatment for your swollen joint or not. Typically you'll need treatment, even if it's just resting the joint at home.

A note from Cleveland Clinic

Joint effusion is where the fluids in the tissues around your joint increase causing your knee, shoulder, ankle or other joint swells up. Treatments help heal the swelling by addressing the cause. There are several actions you can take at home to help heal your joint effusion.

Your swollen joint might be a sign of an injury, infection, arthritis or other condition. It can be unnerving to look at the puffy skin, especially if you don’t know what caused it. Take charge of your health by trying the at-home treatments and also contacting your healthcare provider for help if you have symptoms in addition to joint effusion.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 10/12/2021.

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