What The Patella Sweep Test Is Really Telling You
Posted By: Andy Barker
The patella sweep test is just that…a simple test.
Assessing for the presence of a knee effusion is a simple things…
So why do we as medical professionals make things so complicated sometimes?
If you are a little unsure on what the sweep test is to what it does, I’m not surprised.
The fact that it is also known as the bulge test, effusion wave test, hydro’s tests alongside a whole host of other names is confusing.
There are also other tests to assess for swelling on the knee like the fluctuation test, patella ballottement patella test and the patella tap test.
Wouldn’t it be great if we could just decide on one test, the most valid and reliable test to use…
And even stick to just one name for a test and let that be it!
Regardless of what you call the sweep test, it is a great test to assess the knee and can give you important information about your patient’s injury.
This blog post will focus around the sweep test, summarise the evidence behind the test and give you some tips about what this test actually tells you…
So you can use this information to get the right knee pain diagnosis for your patients or athlete.
What Does The Sweep Test Tell You?
A positive sweep test tells you that there is fluid present within the knee joint (intra-articular).
If the knee is angry and irritated it causes more fluid to be produced.
A positive sweep test therefore tells you that there is excess fluid within the knee joint and in turn…
That something inside the knee (inside the joint) is not happy.
This is great information to have as by the presence of a problem inside the knee…
There are only a few potential structures it could be.
Structures inside the knee include the cruciate ligaments (ACL/PCL), the bony surfaces (tibia and femur) or the meniscus.
The other main structures in the knee, like the tendons (patella or quadriceps) and other ligaments like the MCL or LCL sit outside the joint capsule and as such would not cause an internal knee effusion.
So whilst a positive sweep test does not give you a concrete diagnosis…
It greatly limits what structure could be injured.
Then you can use your other special tests to investigate further.
You could use tests like the Lachman’s Test (ACL), Posterior Draw Test (PCL), McMurrays Test (Meniscal) or joint ROM testing to determine whether or not you have a bony surface injury.
With your patient’s subjective assessment information, and in particular identifying your patient’s mechanism of injury you should be in a great position to make an accurate diagnosis.
The patella sweep test although simple is quite a reliable test.
It has shown to be better, in terms of reliability than both the patella tap test and the fluctuation test for assessing presence of a knee effusion (Fritz et al, 2013).
Remember…Fluid In The Knee Is Normal
It is important to remember that fluid within the knee is normal.
The synovial capsule secretes fluid in to the knee…
Allowing it move better, just like the oil helps all those moving parts in your car.
However, if we see fluid when doing the patella sweep test, this indicates that there is excess fluid within the knee joint, something that suggests injury.
Something is aggravating the knee, which causes an excessive amount of fluid to be produced.
So the presence of an effusion is telling us something inside the knee is injured.
How To Do The Sweep Test
To do the sweep test…
– Position your patient in supine with the knee in full extension and in a relaxed state
– Starting with your hand below the knee joint on the medial (inside of the knee) stroke your hand upwards 3-4 times towards the top of the patella (this sweeping motion is aiming to move any knee effusion from the inside of the joint capsule to the supra-patellar pouch)
– Next, stroke downwards on the lateral (outside of the knee) from just above the supra-patellar bursa towards the lateral knee joint line
Pick One Test: Choose one knee effusion test and stick to it. I use the patella effusion test because it is reliable and easy to do.
Fluid Within The Knee Is Normal: Whilst fluid within the knee joint is normal, a healthy knee will not have a positive sweep test, as this test result indicates excessive fluid within the knee
Practice Your Technique: Practice the test so you are competent and confident with this test and ready to use it for real when you need to
PS. If assessments of the knee are something you would like to learn more about…then just let me know.
I can let you know some of the other tests I commonly use for knee injuries, the ones that you need to make sure you know and can draw upon when you are assessing an acute or chronic knee injury.
And all the other tests that I use as part of my objective assessment so you can be confident you haven’t missed anything and have made the correct diagnosis.
Fritz J. M., Delitto, A., Erhard, R. E. & Roman, M. (1998) An examination of the selective tissue tension scheme, with evidence for the concept of a capsular pattern of the knee. Physical Therapy, 78, pp. 1046-1056.