When the accumulation of fluid is accompanied by inflammation of the connective tissues lining a joint, it is called joint effusion with synovitis.
Joint effusion tends to affect larger joints such as the knee (sometimes called “water on the knee”), shoulder, elbow, or ankle. It is not the same as edema, which is the generalized build-up of fluid in tissues.
Read on to learn more about joint effusion, its causes and symptoms, and what treatments are available.
Joint Effusion Symptoms
Regardless of what is causing the accumulation of fluid in a joint, the symptoms are more or less the same. They can range in severity from mild to debilitating.
Classic symptoms of joint effusion include:
Swelling: Ranging from a mild puffiness to severe swellingPain: Ranging from a dull throb to sharp, stabbing pains that interfere with mobilityRedness and warmth: Associated with inflammation and/or infection
Depending on what is causing joint effusion, other symptoms may develop, including:
Bruising and bleeding in the joint space (such as caused by an injury) Fever, chills, malaise, and weakness (if an infection is involved) A fluid-filled nodule called Baker’s cyst (caused by accumulated fluids that cannot be reabsorbed) Progressive muscle loss (called arthrogenic muscle inhibition, also the result of an injured joint)
What Causes Joint Effusion?
Joint effusion is a sign of joint inflammation and can be broadly classified as either infectious (septic) or noninfectious (aseptic).
Joint effusion caused by infection is referred to as septic arthritis. Aseptic joint effusion can be the result of an injury or arthritis.
Infection
Septic arthritis is most commonly caused by an infection in the joint. The infection can arise from an open wound, like a deep laceration or invasive medical procedure (including a joint replacement).
An infection in the bloodstream—called a systemic infection—can sometimes take hold in a joint and cause localized swelling and effusion.
Certain conditions can increase the risk of septic arthritis, including:
Older age Diabetes Intravenous (IV) drug use Joint replacement Recent joint surgery Arthritis A compromised immune system (such as seen in people with HIV, organ transplant recipients, and people undergoing chemotherapy)
Injury
Injury is a common cause of joint effusion, especially of the knee. Injuries—such as those from a car accident, severe fall, or blunt force impact—can also lead to an effusion.
The injury may also involve bone, connective tissues (such as tendons and ligaments), or joint cartilage (like the meniscus).
Repeated stress on a joint can also cause effusion. This type of overuse injury happens after repeating a movement over and over and is usually related to an occupation or sports.
If the joint effusion is caused by a repetitive stress injury, bursitis (the inflammation of the fluid-filled sac that cushions a joint) and tenosynovitis (inflammation of the tendon sheath where a muscle attaches to a bone) are also common.
Pain, swelling, and stiffness, as well as difficulty extending or rotating the joint, are common symptoms of injury-related effusion.
Arthritis
Joint effusion is common in people with arthritis. The condition can be chronic (slowly developing and progressive) or acute (severe and rapidly developing).
There are two broad categories of arthritis: osteoarthritis (a non-inflammatory form of arthritis also known as “wear-and-tear arthritis”) and autoimmune arthritis (a group of inflammatory autoimmune disorders in which the immune system attacks its own joints).
With osteoarthritis, joint effusion primarily affects the knee and most commonly occurs when there is extensive joint damage. The knee is one of the most commonly affected joints.
With autoimmune arthritis, joint effusion may be chronic but most often occurs in acute episodes (known as exacerbations). Among some of the autoimmune conditions that can cause joint effusion are:
Rheumatoid arthritis: The most common form of autoimmune arthritis, which typically affects joints on both sides of the body Gout: An autoimmune condition that causes swelling and pain, mainly in the big toe, due to the formation of uric acid crystals in the joint space Juvenile idiopathic arthritis: An autoimmune form of arthritis affecting children Psoriatic arthritis: An autoimmune form of arthritis that often accompanies the skin condition psoriasis
Joint Effusion Diagnosis
Diagnosing joint effusion may involve a physical exam, imaging tests, and a lab evaluation of the fluid in your joint. In addition, the healthcare provider will want to review your medical history, current health, and other symptoms.
Physical Examination
Your healthcare provider will examine your joint thoroughly. They will touch (palpate) and work (manipulate) the joint to determine the severity of the condition and the possible causes.
Among some of the possible findings:
With arthritis, the lubricating tissue between the joints, called the synovium, will often feel “boggy” or “mushy. " With the exception of gout, the swelling from most types of arthritis will be gradual rather than swift. Joint infections tend to develop rapidly and cause excessive pain and redness. A torn ligament or knee fracture will almost invariably cause swelling accompanied by the inability to bear weight on the joint.
Imaging Tests
After examining your knee, the healthcare provider may order imaging tests to determine the exact cause of the effusion. Each test has its benefits and limitations.
The imaging tests may include:
Ultrasonography: This non-invasive imaging tool uses sound waves to visualize bone and connective tissues. It can be used to confirm arthritis or inflammation of tendons or ligaments. However, it is less able to visualize soft tissues than other forms of imaging. X-rays and computed tomography (CT): Both of these imaging techniques use ionizing radiation to create images of bone and connective tissue. With CT, multiple X-ray images are combined into three-dimensional “slices” of a body part. CT and X-rays are often best suited for diagnosing bone fractures and arthritis. Magnetic resonance imaging (MRI): This imaging technique uses powerful magnetic fields and radio waves to create highly detailed images of soft tissue. MRI may be best suited to visualize cartilage, ligaments, and other joint structures that the other tests can’t.
Joint Fluid Analysis
In some cases, your healthcare provider may want to drain (aspirate) fluid from a swollen joint. This can help reduce pressure and relieve pain but can also provide valuable information about the cause of the effusion.
The fluid, known as synovial fluid, is removed with a needle and syringe during a procedure known as arthrocentesis. Synovial fluid is usually clear with the consistency of an egg white. Any changes in the appearance, texture, color, or composition of the fluid can provide clues as to the underlying cause of the effusion.
A lab can analyze the fluid to determine if there are excess white blood cells (a sign of infection), uric acid crystals (a sign of gout),or other abnormalities that may narrow the possible causes.
How Is Joint Effusion Treated?
The standard first-line treatments for joint effusion include rest, ice application, immobilization, and a nonsteroidal anti-inflammatory drug (NSAID) like Advil (ibuprofen) or Aleve (naproxen).
If the swelling is especially severe, your healthcare provider may want to aspirate the joint to reduce pressure inside the joint. They may give you a cortisone injection after the procedure to further reduce inflammation and pain.
Infections can usually be treated with a 14-day course of a broad-spectrum oral antibiotic like ciprofloxacin. Other more serious infections, like systemic gonorrhea or methicillin-resistant Staphylococcus aureus (MRSA), may require a two- and four-week course of intravenous antibiotics.
If you have rheumatoid arthritis or another form of autoimmune arthritis, medications may be prescribed to suppress the inappropriate immune response and relieve symptoms. This may involve immunosuppressive drugs like methotrexate or Humira (adalimumab).
Arthroplasty (joint surgery) is reserved for serious joint injuries or to repair joints immobilized by arthritis. Severe cases may require a total joint replacement.
Prevention
While joint effusion can’t always be avoided, there are things you can do to significantly lower your risk of it occurring:
Lose weight: This can reduce stress on the hips and lower extremities. Start a low-impact exercise plan: If you’re experiencing pain in the knee, hip, or ankle, avoid high-impact activities like heavy weightlifting or deep squats. Use resistance training to strengthen joint muscles: This may involve using a leg extension machine for the knees or resistance band training for the shoulder and rotator cuff. Stretch: Perform gentle knee and shoulder stretches before exercise or throughout the day (especially if you’re sitting at a desk for long periods of time). Support your joints: Use elastic knee supports or an elbow brace during contact sports, hiking, and other vigorous physical activities. Don’t overdo it: Never exceed your physical capabilities, especially as you get older. In time, you may want to consider changing the types of sports you engage in to protect your joints (such as switching from running to swimming or cycling). Listen to your body: If you experience sudden or persistent joint pain, get it checked by a healthcare provider sooner rather than later.
Summary
Excess fluid around a joint—called a joint effusion—tends to affect larger joints, such as the knee or ankle. A joint effusion can occur as a result of injury, infection, or different types of arthritis.
In many cases, the excess fluid can be drained while steps can be taken to diagnose and treat the underlying cause (such as using antibiotics to treat a knee infection or immunosuppressants to treat rheumatoid arthritis).
No matter the cause of the effusion, there are steps you can take to better protect the joint and avoid future episodes.
A Word From Verywell
Joint pain can be frustrating, especially when it limits your normal activity. If you experience the build-up of fluid in a joint, even mildly, see your healthcare provider right away to determine the cause. Postponing treatment can result in long-term (and possibly irreversible) damage to your joint and surrounding tissues.
