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Squeezing knee to see more fluid in bursa

November 28, 2013

We sometimes get asked if scanning the suprapatellar bursa for an effusion has any risk of missing an effusion that is located in the knee joint. The risk is pretty low. The bursa and the knee joint are continuous with each other. But if you want to make doubly sure, you can always squeeze the knee on either side of the patella to push any fluid from the knee joint into the bursa. See the video for an example of how squeezing the knee increases the amount of fluid in the bursa.

March 12, 2014 Update
News flash! We now have a new name for this maneuver. It is the “Sonographic Bulge Test”. The term was coined in a recently published article by Drs Checa and Hussein from the Division of Rheumatology at Drexel University in Philadelphia. The article is titled “Sonographic Bulge Test for Small Effusion and Occcult Synovitis of the Knee” and was published this month in the Journal of Clinical Rheumatology. They present a couple of cases describing the technique further. Synovial hypertrophy can be quite dark on ultrasound and mimic an effusion. Squeezing the knee will cause an effusion to be larger, whereas the synovium will stay the same size.


If you want to hear more about septic joints, go to Dr. Joel Yaphe’s podcast at EM Cases: Hot Joints

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  1. Here is another related tip…

    If your practice includes doing steroid injections, you can use knee EDE to guide your injection. It’s done in the same way as one would do an EDE-guided knee aspiration. You’re just injecting fluid instead of aspirating. It’s harder to identify the suprapatellar bursa when there is no fluid in it. There is often a miniscule amount of fluid in a normal knee. If you squeeze the knee on both sides of the patella, you can make this fluid move into the bursa. Seeing this fluid makes it easier to know precisely where the bursa is located. Just send your needle tip right into this little slit of fluid, and then inject your mix of steroid and local anesthetic.