The sweep test is also known as knee hydrops test, knee effusion test, effusion wave test, bulge test, patella sweep test, brush test It is used to assess for joint effusion- presence of increased intra-articular fluid in the knee area.
The sweep test is often paired with the ballottement patella test (in which the examiner strokes the proximal hand on the thigh towards the knee and taps on the patella with the index finger of his distal hand) and the fluctuation test (in which the examiner is placing his fingers of one hand near the apex and with the other hand near the base of the patella, while the fingers are used to alternate press and feel the fluid displacing).
Clinically relevant anatomy
Click here to get more information of anatomy of the knee.
To test for minimal joint effusion. Note that even a healthy joint has a normal amount of fluid in the joint capsule, but ‘’minimal’’ suggests there is an excess of fluid which cannot be noticed on sight but can be tested with the sweep test.
- The patient lying in supine position with the knee in full extension and relaxed, the examiner puts his hand beneath the medial tibiofemoral joint line.
- Then he strokes his hand upwards and towards the suprapatellar bursa 2 -3 times in a sweeping motion in an attempt to move the effusion from the inside of the joint capsule to the suprapatellar pouch.
- The examiner then strokes downwards on the lateral aspect of the knee just superior to the suprapattelar bursa towards the lateral joint line. If the test tests positive you’ll detect a small wave or bulge on the medial aspect of the knee, just inferior to the patella within a few seconds.
Research by Fritz et al. has shown that the inter-rater reliability of both tests was rather poor: fluctuation test, қ = 0.37, patellar tap test, қ = 0.21 (Cohen's kappa coefficient was used). In contrast to the sweep test which scores very highly in inter-rater reliability (қ = 0.75)observed as a proportion of the maximum possible kappa score, with a percent agreement of 73%. Fifty-four of 75 pairs of tests had perfect agreement. Only with 5 pairs there was disagreement of 2 grades, and in that marge, there was no disagreement of greater than 2 grades ever.
It can be measured in quantity on a 5-point grading scale.
- 0 - no fluid-wave while performing a downward stroke.
- Trace - a small bulge on the medial aspect of the knee
- 1+ - a larger bulge
- 2+ - medial fluid returns to its position without performing a downward sweep
- 3+ - excess of fluid that makes it impossible to stroke the medial fluid away
- David J. Mathison, MD*Þ and Stephen J. Teach, MD, MPH*Þ Pediatric Emergency Care Issue: Volume 25(11), November 2009, pp 773-786 [level of evidence: B]
- Fritz JM, Delitto A, Erhard RE, Roman M. An examination of the selective tissue tension scheme, with evidence for the concept of a capsular pattern of the knee. Phys Ther. 1998;78:1046-1056; discussion 1057-1061. http://ptjournal.apta.org/content/78/10/1046.full.pdf+html [level of evidence: B]
- Interrater Reliability of a Clinical Scale to Assess Knee Joint Effusion Patterson Sturgill et al.; Journal of Orthopaedic Sports Physical Therapy 39 (2009) 845-849