What Causes Fluid Buildup in the Knee?

Pain or stiffness in the knees may result from fluid buildup in the knee. This is known as joint or knee effusion, a common condition caused by inflammation, injury, infection, or other factors. This article will cover some common causes of fluid buildup in the knee joint. We’ll also discuss potential options for treatment and prevention.

Causes of Fluid Buildup in the Knee

The most common causes of fluid buildup in the knee joint are inflammation, injury, and infection. This can lead to reduced movement, difficulty walking, and other complications that may require serious medical intervention.

I. Inflammation

Inflammation causes the knee joint to produce excess fluid that can build up in and around the knee. It’s one of the most common causes of fluid buildup. One source of inflammation, osteoarthritis, is so common that an estimated 46% of people may develop it during their lifetime. Women above 40 are particularly at risk of developing this condition.

Other possible causes of inflammation are:

  • Rheumatoid arthritis
  • Pseudogout
  • Bursitis
  • Tendonitis
  • Cysts
  • Tumors
  • Injury
  • Gout

II. Traumatic Event

Overuse injuries or tears can cause injury leading to fluid buildup. Many injury-related cases of fluid buildup result from:  

  • Torn ligaments, especially the anterior cruciate ligament (ACL)
  • Overuse irritation from strains or sprains
  • Broken bones
  • Cartilage or meniscus tears

III. Infection

Another source of fluid buildup in the knee joints is an infection that reaches the joints through the bloodstream. This can result from injections, injuries, or surgery. Some different types of bacteria, viruses, and fungi that can infect knee joints include:

  • Streptococci
  • Staphylococci
  • Gonococci
  • Haemophilus influenzae
  • Gram negative bacilli
  • Viruses (such as HIV and others)

Symptoms of Knee Effusion

The symptoms of fluid buildup in the knee joint can vary depending on the cause. Common symptoms include:

  • Aching pain
  • Swelling
  • Fever
  • Redness or warm skin
  • Stiffness or heaviness in the affected area
  • Decreased range of motion
  • Difficulty walking
  • Difficulty bending or straightening your knee

Treating Fluid Buildup in the Knee

Since various factors can cause fluid buildup, it’s essential to understand the relevant cause before determining the best course of treatment. Your doctor will need to examine your medical history and physical condition. They may also order blood tests and imaging tests such as an x-ray, MRI, or CT scan to confirm the diagnosis. 

In mild cases of inflammation or injury, self-care measures may be sufficient. For example, you could try home remedies such as:

  • The RICE method (Rest, Ice, Compression, Elevation)


  • Over-the-counter pain relief medication such as acetaminophen or ibuprofen

However, if you are experiencing a high level of pain or your knee becomes red or warm to the touch, contact your doctor immediately. This could be a sign of infection and requires medical intervention. Here are some examples of different treatment options that your doctor may prescribe for swollen knee joints.

I. Anti-inflammatory medications

Anti-inflammatory medication such as ibuprofen or naproxen can help reduce swelling and pain. Steroids may also be orally administered or injected to block inflammation. Antibiotics are used in cases where the knee is infected. For example, your doctor may prescribe antibiotics to treat septic arthritis.

II. Arthrocentesis

Arthrocentesis is the procedure of draining synovial fluid from your swollen joint. This can help relieve pressure in the joint, and the fluid can be tested to determine the cause of the swelling. The fluid is checked for the presence of blood, bacteria, or crystals common to gout.

Sometimes, the doctor may inject medication such as a corticosteroid into the joint to help reduce inflammation. Arthroscopy is a procedure where the doctor inserts a lighted tube called an arthroscope into the knee joint through a small incision. Tools attached to this tube can be used to repair tissue damage inside the knee.

III. Physical Therapy

Physical therapy is used to restore strength and movement to the knee joint. The type and duration of treatment depend on the cause of fluid buildup and its severity. Knee braces can help relieve pressure on the joint and reduce pain. This allows the wearer to improve their range of motion and daily activity levels.

Preventing Fluid Buildup in the Knee

Since various factors can cause fluid buildup, it isn’t easy to prevent it altogether. However, avoiding activities that cause inflammation, injury, or infection can reduce your risk of swollen knee joints. If you’re susceptible to injuries or have a chronic health condition, take extra precautions when exercising and take note of the following advice:

– Lead a healthy lifestyle
– Maintain a healthy weight
Wear an unloader knee brace
– Exercise with caution/awareness

Leading a healthy lifestyle, maintaining a healthy weight, and wearing a knee brace are different ways to help lessen the wear and tear or risk of damage to joints that can lead to injury or fluid buildup. Exercise is crucial to building strong muscles around joints that can relieve pressure on the joint.

If you have weak joints, focus on building your strength in those key areas. However, choose low-impact exercises such as swimming or upper body exercises to avoid stressing your joints if you have previously suffered a knee injury. Minimize running, jumping, or other high-impact actions unless your joints fully heal. In addition, wear appropriate footwear and use proper form.

Risk Factors & Complications

There are several risk factors for fluid buildup in the knee joint. These include:

Age: People above the age of 40 are more at risk for swollen knees, especially in cases caused by arthritis

Weight: Excess weight can place additional stress on joints, leading to inflammation or injuries

Gender: Females are more likely than men to develop osteoarthritis, which can cause fluid buildup in the knee 

Lifestyle: People who lead a sedentary lifestyle are more likely to experience fluid buildup in the knee joint. At the same time, high-impact sports such as basketball should be avoided if joint pain sufferers.

If left untreated, fluid buildup in the knee joint can lead to further complications. These can include osteoarthritis, joint stiffness, and cartilage damage.

Key Takeaways

The treatment for fluid buildup in the knee joint will depend on the underlying cause. The best way to prevent fluid buildup in the knee joint is to avoid activities that can cause inflammation, injury, or infection. If you’re experiencing symptoms of fluid buildup in the knee joint, seeking medical attention is essential to avoid further complications. 

For people suffering from swollen knee joints, a knee brace can help relieve pressure. The Icarus Ascender Brace reduces knee pain significantly and can unload up to 40 pounds from your knee. With its form-fitting design and adjustable tension, the Ascender can help restore mobility and get you back to doing what you love.

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