Ballottement test


The ballottement test also is known as the Patella tap test or the ballottement patella sign. Ballottement means “a tossing about.” and it was coined from a french word. The test is usually used to check for knee joint effusion.


To start the test, the patient/client lies supine on an examination table. The therapist uses the non-dominant hand to apply a series of downwards stroke from thigh to leg and then firmly grasps the upper part of the knee just above the patella. One finger or the thumb of the dominant hand is used to push the patella backward against the femur. An increased patella waving motion or spongy joint feeling suggests the test is positive for joint effusion[1]. Then the test is repeated on the contralateral joint for comparison.



Patellar tap has been shown to have an inter-observer kappa agreement of −0.02 to 0.75 with sensitivity ranging 18.2–85.7% and specificity 35.3–93.3%, both higher with larger effusions.[3]


  1. Medisavvy. Patellar Ballottement sign. 2016. (assessed 21 January 2020)
  2. Clinical Examination Videos. Patella tap test - Ballottement test. Available from:[last accessed 12/1/2020]
  3. Maricar N, Callaghan MJ, Parkes MJ, Felson DT, O'Neill TW. Clinical assessment of effusion in knee osteoarthritis-A systematic review. Semin Arthritis Rheum. 2016;45(5):556–563. doi:10.1016/j.semarthrit.2015.10.004