Patellar Tap Test / Ballotement Test

Execution:

1. Patient is in supine lying position with an extended knee
2. The examiner then strokes distally on the patient’s knee to milk fluid behind the patella
3. The examiner’s other hand strokes from distally to medially on the patient’s tibia and stops below the apex of the patella
4. While applying downward pressure, the examiner uses the index finger to tap onto the patella

 

Positive Outcome: The patella “floats” back to its normal position after the tap or the examiner can hear a click when pushing onto the patella, which indicates accumulation of fluid underneath it

Study	Reliability	Sn	Sp	LR+	LR-
Kastelein et al. (2009)	NA	83	49	1.6	0.3
Comment: The authors mention that a negative Ballotement Sign and the absence of self-reported swelling can reasonable exlude the presence of knee joint effusion