Everything You Need To Know About Joint Effusion


There is normally a small amount of fluid surrounding a joint, and this is necessary for movement. Basically, joint effusion is an abnormal amount of fluid in and around the joint.

The knee is a common joint that is affected. “Water on the knee”, is a common non-medical term that is used for joint effusion of the knee.


About Joint Effusion

A “symptom” is something that the patient experiences and a “sign” is something that is observed by someone else, or a doctor will usually notice. For instance, drowsiness may be a symptom of being overly tired. Dilated pupils, on the other hand, are considered to be a sign that you have just finished a thorough eye exam.

Now that we identified the difference between symptoms and signs – relating this to joint effusion will depend greatly on the cause of the fluid build-up.

An example of a symptom would be that someone would be unable to put weight on the knee, or even bending or straightening the knee is difficult without great pain.

A sign would be swelling and puffiness on and around the knee cap, and when compared to the other knee, this sign would be very obvious. Another sign would be a bruise, especially, if the knee (or other joint) was involved in a physical trauma.


Joint effusion has a variety of causes, including, but not limited to physical trauma, viral infections, and inflammation due to certain types of arthritis. Swelling and an increase in protective fluid is a natural reaction of the joint, especially, if the ligament has been injured. On the other hand, there could be an underlying medical condition that is the cause of the extra joint fluid.

A person that is obese will put more weight on a joint, and over time, excessive amount of joint fluid can build up and cause the joint to deteriorate in a quicker manner.
Some health conditions associated with swollen joints include, but are not limited to:

Osteoarthritis is something that is associated with aging, but it can also occur after an injury. With this condition, the cartilage is worn down to the point that there is no (or very little) cushioning between the bones, and painful swelling occurs.

Rheumatoid arthritis (RA) is not a condition that is limited to the elderly, as RA can even affect young children. Common symptoms associated with this condition are pain, stiffness and swelling in the joints.

Gout is a type of arthritis that strikes quickly, and it can become so painful, that even the weight of a light bed sheet can be extremely uncomfortable.


Having an X-ray conducted will help to verify that no break has occurred, or that a joint is not dislocated, or if there are signs of osteoarthritis. A Magnetic Resonance Imaging (MRI) machine is used to detect abnormalities in the joint and/or bone structure. Tears in the tendons, cartilage and ligaments are some things that an MRI will show.

A doctor will do a physical exam of the joint, but an ultrasound machine is used to confirm a diagnosis of joint effusion.

A blood test may also be conducted, especially, if the attending physician suspects rheumatoid arthritis, gout, or an infection. A blood test will reveal a white blood cell count (indicating the presence of an infection) or levels of C-reactive proteins. Lyme’s disease is also a recommended test when joint inflammation is present, as this could be the underlying cause of the problem.

An aspiration (also referred to as arthrocentesis) is the most common and effective form of treatment. An ultrasound machine is again utilized, to guide the treatment of an aspiration. Fluid is withdrawn from the joint using a syringe. The fluid is analyzed for bacteria, uric acid crystals or calcium pyrophosphate dihydrate crystals (that is usually found in gout).


Treatment should be sought out by a health care professional, and it is important to note, that many joint effusion treatments are based on the cause of the condition. There is no standard type of treatment, except for “water on the knee”, and that would be an aspiration (described above).

Corticosteroid injections and antibiotic drugs may be used to treat an inflammation associated with an infection. Replacement of the joint may be necessary in some cases.

In addition to medical care, some general home care should be an increase in rest and elevation of the joint. If joint effusion is related to a physical injury, icing is also a recommended self-care treatment (ice should be applied to the area in 15 minute intervals).

Physical therapy is also a recommended treatment, in order to strengthen the area that surrounds a weakened joint.