Procedure
- The patient lies in supine position with extended hips and knees.
- The quadriceps femoris muscle should be relaxed. Check this by palpating the muscle.
- With a sweeping movement using the entire hand, the examiner should fully empty the suprapatellar recess by stroking in the distal direction.
- With fingers of the other hand, the examiner pushes firmly on the patella and observes whether ballottement occurs (patellar tap test) [Figure 75].
- If so, the test is positive – there is (considerable) fluid accumulation.
Figure 75
If the patient is suspected of having minor fluid accumulation and the aforementioned test is negative, the following variant of the test can be applied [Figure 76]:
- Place the fingers and palm of the hand at the height of the medial joint space.
- Use that hand to stroke any possible fluid there, cranially towards the suprapatellar recess and keep this hand in that position.
- Using fingers and palm of the other hand, empty the suprapatellar recess by stroking in the distal direction at the lateral femoral condyle.
Figure 76
In the case of minor fluid accumulation, the synovial membrane that was initially emptied by stroking in the proximal direction, will now fill with fluid at the height of the medial femoral condyle (Katz symptom).