Knee
Fluctuation test for effusion
Sweep test / ballottement
- What you examine
- Fluid in the knee joint and how much of it there is.
- Procedure
- Supine, knee extended. Sweep the fluid with a flat hand from the medial recess proximally and laterally, then sweep back from lateral. Watch whether the medial hollow refills.
- Positive when
- A visible fluid wave refilling the medial hollow within a few seconds.
- What the test is worth
- Sensitive to small amounts of fluid, down to about 4 ml. With a large effusion patellar ballottement is preferable.
- Caution
- Effusion within two hours of trauma indicates blood in the joint, and that means a cruciate rupture, a fracture or a patellar dislocation until proven otherwise.
- Joint
- Knee joint
- Body region
- Knee