Ballottable Patella Sign


Ballottable Patella Sign, Ballottement Test, Patellar Tap

  • Indication
  1. Evaluation for large Knee Joint effusion
  • Technique
  1. Patient lies supine on table
  2. Examiner forces fluid from suprapatellar pouch
    1. Firmly grasp just above Patella with one hand
    2. Forces Joint Fluid between Patella and femur
  3. Examiner pushes Patella downward into femur with 2-3 fingers
    1. Use a quick sharp motion in pushing the Patella down
    2. Assess for palpable click on Patella striking femur
  • Interpretation
  • Positive test suggests large effusion
  1. Large Knee Joint effusion: Palpable click present as Patella strikes the trochlea
  2. No joint effusion (normal): no click palpated
  • References
  1. Bates (1991) Physical Exam, Lippincott
  2. Kastelein (2009) Arch Phys Med Rehabil 90(1): 82-86 [PubMed]