Use one hand to firmly stroke downward from the mid-thigh toward the kneecap. This "milks" fluid out of the suprapatellar pouch and into the space behind the patella.
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.
The patella is already in contact with the bone; there is no sensation of floating or clicking.