Joint effusion: symptoms, causes, diagnosis, treatment


Joint effusion is a condition in which there is excess fluid in or around the joint, usually the knee. Commonly known as knee water or knee fluid, it is most often caused by infection, injury, or arthritis. Not only does excess fluid cause swelling, it can also cause pain and stiffness.

The effusion usually affects larger joints such as the knee, shoulder, elbow, or ankle. This is not the same as edema , another type of edema caused by inflammation, allergies, heart failure, and other conditions.

Read on to learn more about joint effusion, its causes and symptoms, and available treatments.

Illustration by Emily Roberts, Get Drug Information

Symptoms of joint effusion.

Regardless of the cause of the fluid in the joint, the symptoms are similar. The severity of symptoms can vary from person to person. Classic joint effusion symptoms include:

  • Edema : from mild generalized edema to severe swelling and swelling.
  • Pain : movement that limits from dull to sharp.
  • Stiffness : limiting the range of motion of a joint or limiting it entirely.
  • Redness and warmth : associated with localized inflammation .

Depending on the cause of the joint effusion, you may have other symptoms, such as:

  • Bruising and bleeding in the joint space (due to injury)
  • Fever, chills, malaise, and weakness (if infected)
  • Progressive loss of muscle mass (due to prolonged arthritis, also called arthrogenic muscle depression ).

A common complication of joint effusion is the formation of a fluid-filled nodule known as a Baker's cyst in the joint space. This is because the amount of fluid in the joint is so great that the body cannot reabsorb it. While a smaller Baker's cyst may not cause symptoms, large cysts can sometimes be felt and cause pain when moving.


An effusion is a sign of joint inflammation and can be classified as infectious (septic) or non-infectious (aseptic). The excess joints caused by an infection is called " septic arthritis ." Aseptic effusion in a joint can result from trauma or arthritis.


Septic arthritis is most commonly caused by an infection in the joint. The infection can come from an injury, such as deep trauma or a medical procedure. An infection in the bloodstream, also called a systemic infection, can invade the joint and cause swelling and excess fluid.

Symptoms caused by an infection are usually rapid and severe. In the context of a joint infection, the effusion is usually very painful, especially with movement.

Certain conditions can increase your risk of developing septic arthritis, including:

  • Advanced age
  • Diabetes
  • IV drug use
  • Endoprosthesis
  • Recent joint surgery
  • Arthritis
  • An impaired immune system (eg, in advanced HIV infection, organ transplant recipients, or patients undergoing chemotherapy)

Fungal, viral, and parasitic causes are most commonly associated with a weakened or suppressed immune system.

Trauma, damage

Sports injuries are a common cause of joint effusion, especially the knee. Injuries, for example from a car accident, serious fall, or forceful impact, can also cause a spill. The injury may involve bone, connective tissue (such as tendons and ligaments), or articular cartilage (such as meniscus ).

Repetitive stress on the joint can also cause stroke. This type of injury occurs after repeated repetition of movements and is usually associated with activities or sports. Bursitis (inflammation of the fluid-filled sac that cushions the joint) and tenosynovitis (inflammation of the tendon sheath where the muscle joins the bone) are also common in people with outflow into the joint due to repetitive strain injuries. .

Pain, swelling, stiffness, and difficulty extending or rotating a joint are common symptoms of trauma-related effusion.


Fluid build-up and joint inflammation are common in arthritis patients. Arthritis can be ongoing (chronic) or cause sudden (acute) bouts of inflammation that can lead to swelling.

Generally speaking, there are two types of arthritis:

In osteoarthritis, joint effusion primarily affects the knee and is most commonly associated with extensive joint damage. In autoimmune arthritis, joint effusion can be associated with chronic inflammation or acute flare-ups (known as seizures or flare-ups).

Attacks are especially common in gout, an autoimmune disorder characterized by the accumulation of uric acid crystals in the joint space (mainly in the big toe). Gout symptoms can be severe and start quickly, which can lead to excessive fluid secretion around the joint.

Joint effusion can be caused by arthritis, injury, or even infection. The symptoms are the same regardless of the cause. Understanding which conditions can cause joint effusion and how to tell if you have one can help you get prompt treatment.


Diagnosis of joint effusion may include physical examination, imaging, and laboratory evaluation of the fluid in the joint. In addition, the doctor will also check your medical history, current health, and other symptoms.

Physical exam

Your healthcare provider will carefully examine your joint. They will touch (feel) and bend (manipulate) the joint, which can say a lot about the causes of the effusion. For instance:

  • In arthritis, the lubricating tissue between the joints, called the synovium , will appear boggy ('soft'). With the exception of gout , swelling in most types of arthritis will be gradual rather than rapid.
  • Joint infections tend to develop quickly and cause excessive pain and redness.
  • Acute edema accompanied by an inability to bear weight may indicate a ligament tear or knee fracture.

They will also be able to determine if a Baker's cyst has formed.

Visual tests

After examining your knee, your doctor may order pictures to determine the exact cause of the effusion. Each test has its own advantages and limitations. The tests may include:

  • Ultrasound uses sound waves to visualize bones and connective tissues. It can be used to confirm arthritis or inflammation of tendons or ligaments. Although ultrasound is non-invasive and portable, it has the disadvantage that it is less capable of soft tissue imaging than other forms of imaging.
  • X- rays and computed tomography (CT) , which use ionizing radiation, are best for diagnosing and characterizing bone fractures and arthritis.
  • Magnetic resonance imaging (MRI) uses magnetic fields and radio waves. MRI is used to visualize soft tissues, cartilage, and joint structures that are not possible with other tests. This is sometimes associated with the use of intravenous contrast media.

Collaborative fluid analysis

Your healthcare provider may want to drain (aspirate) fluid from the swollen joint. This will help relieve pressure and relieve pain a bit. A fluid known as synovial fluid is removed during a procedure called arthrocentesis . Your healthcare professional will examine the fluid and may also send the sample to a laboratory for analysis.

Synovial fluid is usually clear and has the viscosity of an egg white. Any change in its appearance, texture, and cellular composition can provide clues to the underlying cause of the joint effusion.

Synovial fluid can provide valuable information, including:

  • Cloudy fluid may indicate rheumatoid arthritis due to an increase in white blood cells (usually more than 10,000 per cubic millimeter).
  • A greenish-yellow fluid can indicate an infection, especially if the white blood cell count (WBC) exceeds 20,000 per cubic millimeter. Traces of pus can also be seen.
  • The golden liquid is commonly associated with gout. Microscopic examination may also reveal uric acid needle crystals.
  • Bloody or pinkish fluid may indicate blood, a classic symptom of joint injury.
  • A clear fluid is commonly seen in osteoarthritis because it is not associated with inflammation. White blood cells are usually below 2000.

If an infection is suspected, the laboratory may also perform a culture to cultivate and isolate the bacteria or fungi that are causing the disturbance.

The diagnosis of joint effusion often includes both physical examination and imaging tests, such as ultrasound, X-rays, and even MRI. If your healthcare provider drains fluid from your knee, they will examine it and may send a sample to a laboratory for analysis.

Watch out

Standard first-line treatment for joint fluid includes rest, ice , immobilization, and non-steroidal anti-inflammatory drugs (NSAIDs) such as Advil (ibuprofen) or Aleve (naproxen).

If your swelling is particularly severe, your healthcare provider may drain fluid as part of your treatment. After your procedure, you may be given a cortisone injection . It can quickly reduce pain and inflammation, especially if there is severe injury or joint damage as a result of arthritis.

Infections can usually be treated with a 14-day course of an oral broad-spectrum antibiotic such as ciprofloxacin. Other more serious types, such as those caused by systemic gonorrhea or methicillin-resistant Staphylococcus aureus (MRSA) , may require two to four weeks of intravenous antibiotics.

If you have rheumatoid arthritis or another form of autoimmune arthritis, there are steps you can take to manage your condition. This may include the use of immunosuppressants, such as methotrexate and Humira (adalimumab) , to moderate the abnormal immune response.

Arthroplasty (joint surgery) is used for severe joint injuries or to repair immobilized joints due to arthritis. In severe cases, a joint replacement may be required.


While you can't always avoid a shared effusion, there are things you can do to significantly reduce your risk:

  • Lose weight. This can reduce stress on the hips and lower extremities.
  • Embark on a low-impact exercise plan . If you feel pain in your knees, hips, or ankles, avoid strenuous activities like weight lifting or deep squats.
  • Use resistance training to strengthen the muscles in and around the joint . This may include the use of a knee extension machine or resistance training for the shoulder and rotator cuff.
  • Stretch . Do light knee and shoulder stretches before exercising or during the day if you are sitting at a desk for a long time.
  • Support your joints . Wear an elastic knee support or knee brace during contact sports, hiking, or other activities.
  • Don't overdo it . Never exceed your physical capabilities, especially as you age. This may include changing the sports you play (for example, switching from running to biking) or even using a chair for hard-to-reach objects.
  • Listen to your body . If you experience sudden or persistent joint pain, see your doctor sooner rather than later.


The excess fluid around the joint, called an effusion, affects larger joints, such as the knees. Joint effusion can be the result of injury, infection, or various types of arthritis. In many cases, the fluid can be drained and steps can be taken to correct the cause (for example, antibiotics to treat an infection). Regardless of the cause of the joint effusion, you can take steps to prevent future episodes and improve joint health.

Get the word of drug information

Joint pain can be frustrating, especially when you limit your normal activities. If you experience fluid build-up in a joint (such as your knee, shoulder, elbow, or ankle), speak with your doctor immediately to determine the cause. Delaying treatment can lead to long-term damage to joints and tissues.

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