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.
While maintaining pressure with the first hand, use the index finger of the other hand to sharply push the patella downward toward the femur (thigh bone). Findings: ballottement
The clinician inserts two fingers into the vagina and gives a sharp upward tap against the lower segment of the uterus. If the fetus is present and not yet engaged in the pelvis, it will float upward and then fall back, tapping against the clinician’s fingers. This is the most frequent use of the term