Patellar Tap / Ballottement Test Special Test
Orthopedic Physical Examination & Clinical Assessment Guide
What is it used for?
- Detecting Major Knee Effusion (swelling).
How to Perform
- Position: Patient supine, knee extended.
- Action: Milk fluid down from the thigh. Tap (push) the patella quickly against the femur.
Interpretation of Results
- Positive Test: The patella “floats” and bounces back up (ballottable), indicating significant fluid.
Clinical Context & Limitations
The Patellar Tap / Ballottement Test should be considered as one component of a comprehensive musculoskeletal assessment. No single special test has perfect diagnostic accuracy; thus, clinical decision-making should integrate test results with patient-reported symptoms, mechanism of injury, functional impairment, and relevant imaging.
Clinicians should be aware of potential false-positive results in patients with pain sensitisation, muscle guarding, or poor relaxation. For the Knee region, combining the Patellar Tap / Ballottement Test with complementary examination tests significantly improves overall diagnostic confidence.
References
- Magee, D. J. (2021). Orthopedic Physical Assessment.
