Water on the Knee (Knee Effusion)

Water-on-the-Knee-Knee-EffusionWater on the knee is a general term that people use to refer to knee swelling from fluid build up around the knee joint. However, the fluid on the knee is not actually water.

Rather, it is synovial fluid which is an egg like substance that protects the knee joint. Water on the knee is also commonly known as swelling of the knee or medically known as knee effusion.


There are 2 main causes of water on the knee: knee arthritis and overuse injury. However, there are other causes of knee effusion which include:

  • Osteoarthritis – an abnormalities involving the deterioration of the joints.
  • Rheumatoid Arthritis – a chronic inflammatory disorder that affects the joints.
  • Broken bones – a fracture.
  • Meniscus tear a tear of the C shaped cartilage located in the knee.
  • Ligament tear – a tear of 1 of the 4 ligaments in your knee. ACL, PCL, MCL and LCL.
  • Infection – an agent or a contaminated substance responsible for the onset of someone becoming infected.
  • Pseudogout – a form of arthritis characterized by the onset of painful swelling in one or several joints.
  • Kneecap Bursitis – the swelling of the bursa.
  • Overuse – a use of the knee in excess.
  • Gout – a disease in which uric acid causes arthritis.
  • Cysts – a closed sac. Read more about Baker’s Cyst.
  • Tumors – an abnormal growth of body tissue.


Water on the knee is not usually associated with pain, rather discomfort. Although it is a symptom, swelling is usually the first sign of knee effusion. Other symptoms may include:

  • Swelling – one knee may swell noticeably in comparison to the other knee.
  • Stiffness – your knee joint might stiffen up if excess fluid builds.
  • Redness – the swelling may cause redness.
  • Warmth – the swelling may cause the knee to become warm to the touch.
  • No Relief – you might experience little relief after taking medication.
  • Discomfort – you may feel various levels of discomfort depending on the cause of your water on the knee.
  • Pain – if swelling and build up continues, pain may become severe.


If you feel you have water on the knee (knee effusion) contact your doctor to be diagnosed properly. He or she will perform a physical examination and evaluate your knee injury. In addition, your visit may include:

  • Joint aspiration – removing fluid from the area around the knee joint using a needle and syringe.
  • Imaging – a high-energy stream of electromagnetic radiation. Also known as an X-Ray.
  • MRI – Magnetic Resonance Imaging (MRI) is a technique that uses radio waves to create images.
  • Blood test – a test to analysis your blood.


Treatment for water on the knee will depend on the severity of your knee swelling. However, some of the options to reduce the swelling are:

  • RICE – Rest, Ice, Compress & Elevate. Click here to read about RICE.
  • Aspiration – removing fluid from the area around the knee joint using a needle and syringe.
  • NSAID’s – Non Steroidal Anti-Inflammatory Drugs.
  • Antibiotics – an agent that kills bacteria.
  • Corticosteroids – a substance that includes steroid hormones.
  • Arthroscopy – an instrument inserted into the joint to repair damage.
  • Joint replacementsurgery in which the joint surface is replaced with an orthopedic prosthesis.

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Water on the knee is usually associated with a chronic health condition. It is also associated with a traumatic injury. However, you might find you can lessen your chances of getting water on the knee (knee effusion) from doing the following:

  • Regular Doctor Visits – it’s common to neglect or forget to go see the doctor. However, if you have a chronic health condition or traumatic injury you will not be able to heal properly without regular visits.
  • Take Your Medication – neglecting to take your prescribed medication or stopping it too soon may lead to prolonged knee effusion.
  • Strengthen Leg Muscles – support your knees by strengthening your leg and thigh muscles.
  • Listen to Your Knees – your knees hold 75% of your body weight every day. Maintain a healthy weight, exercise regularly and listen to your knees.

Other articles you should read:

Have You Ever Had Water on the Knee (Knee Effusion)? Please Comment Below.

Article last updated on January 8th, 2019, first published on July 15, 2013.

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