What Is a Ballottement?

Ballottement is a physical examination technique a care provider uses to check for buildups of fluid. It is most commonly employed in a knee examination, but can also be used in evaluation of other joints as well as the abdomen. Large deposits of fluid can be a cause for concern, as they may indicate an ongoing inflammatory process. If the test shows the presence of fluid, the care provider may ask to take a needle aspiration biopsy, where a thin needle is inserted into the area and used to draw up a sample of fluid for evaluation.

In the case of a knee examination, the care provider performs ballottement by gently pushing down on the patella. It should move freely, without any clicking or sluggishness. If the patella does not move smoothly, or it rebounds after the examination, this can be a sign that fluid is present in the joint. The fluid may be visible or palpable in some cases, depending on the nature of the swelling. Similar palpation tests can provide information about fluid buildups in other areas of the body.

This test allows the care provider to determine if the structure of interest appears to be floating, rather than articulating with neighboring structures. This can indicate that fluid is causing swelling and separation. In knee ballottement, for example, the kneecap may feel slightly boggy during the examination, suggesting that it is pushing through fluid. Pressure inside the joint can also be so intense that it is difficult to push the kneecap at all.

Needle aspiration biopsies can provide important information about the nature of fluid buildups noted during ballottement. They may reveal that large numbers of white blood cells are present, indicative of infection. Abnormal cells or organisms in the sample can also be signs of disease. Some doctors may quickly examine the sample in the office to collect immediate information about the situation. Others may prefer to send it to a pathologist for skilled evaluation.

Immediate treatment for swellings can depend on the cause. Severe pressure detected in ballottement may require the placement of drains to allow the fluid to exit. Medications can reduce inflammation and swelling, as can the application of ice and cool compresses. Emergency measures like resting and icing an inflamed knee may be recommended to control the swelling until the physician can figure out the cause, at which point a more permanent treatment can be provided.