Ballottement

This test is highly specific for large effusions but may miss smaller amounts of fluid, which are better detected using the Bulge Sign . 2. Obstetric Ballottement

This is the most frequent use of the term. It is used to identify a "floating" kneecap, which indicates a moderate-to-large accumulation of fluid (effusion) within the knee joint.

In pregnancy, ballottement is a "probable sign" used to detect the fetus as it floats in amniotic fluid.