How To: Ultrasound of the Knee - SD

Basic Knee Demonstration

We're going to do a basic knee demonstration
using the Phillips IU 22 system.
I have a linear 12 transducer,
which is the best for knee examinations.
I'm gonna start in the suprapatella area.
You can see here the quadriceps tendon is attaching onto the
patella to its superior portion
and we can scan through medially
to laterally making sure we cover the entire tendon.
It is quite a thick tendon,
quite a wide tendon side to side.
All ultrasound needs
to make sure you cover the entire area
and sweep back and forth.
You'll see below in the suprapatella fossa,
there's a small amount
of fluid here and that's quite normal.
Most people have a little bit of fluid.
When it gets an excessive amount, say we're sort
of starting to get to this level.
That would be called a suprapatella effusion,
and that's certainly something that ultrasound can guide a
needle to drain if we go down to a transverse section.
Now watching the quadriceps tendon here, as I said,
it's quite a wide tendon side to side, so
that's why the linear 12 is a good choice
because it's got such a wide face.
You can see here this is the tendon in its entirety,
looks nice and homogenous.
It's quite an echogenic tendon.
As we scan down towards the patella, again,
you come into this small amount of fluid here, again,
quite normal and nothing to worry about,
and we scan all the way down
until it's insertion on the patella.
Again, you have to be a little careful with
a nicer trophy here
and make sure that you heel toe the probe effectively
because if we heel more than a few degrees away from
perpendicular, you can see
how hypoechoic this tendon becomes.
And that's indicative of tendon tearing
or tendon inflammation, tendonosis.
You don't wanna create a false positive there.
So just make sure that you keep a hundred percent
perpendicular to the tendon.
You can see that the fibers fill in here and it becomes nice
and echogenic, and that's exactly what you're looking for.
Underneath you'll see a small amount of cartilage.
Again, this is quite normal.
Try not to mistake this for fluid
and again, just tracking it all the way down onto
that superior portion of the patella.

Prepatellar Area

We're going now to the prepatella area of the knee.
There is a bursa that lives in this spot.
Patients will invariably present with inflammation
or a bump on top of their knee.
You need to use a fair amount of gel
for the prepatella portion.
You can see here I've got a little bit
of a standoff created by the thick gel
because the prepatella bursa,
it sits in this subcutaneous region above the patella tendon
or the patella ligament.
And if you push too hard,
you can completely compress it.
So you can just imagine if there was a line
of fluid just sitting above the patella tendon here,
above the mid portion of the patella.
That's where you're gonna find the bursa.
And again, it is indistinguishable
unless you have fluid in there.
But again, make sure that you are not pressing too hard
and obliterating the bursa completely.

Infrapatellar Portion

On we go to the infrapatella portion of the knee.
Infra obviously meaning below.
So below the patella here,
this is the superior portion of the patella tendon.
Again, you see it's a nice homogenous tendon.
Again, some people call it the patella ligament.
Either is perfectly fine.
The fibular pattern of the tendon is nice and smooth
and even there's no interruption to the pattern.
The linear echogenic pattern here below,
there's a thing called fat pad.
Again, quite normal for it
to be a hypoechoic soft tissue down here.
And again, just sweep side to side.
Make sure you're covering the entire tendon
from medial to lateral.
Again, with the 12 megahertz transducer, we can almost
get the entire length of the tendon.
It's quite a long tendon and it's distal attachment here.
You can see it fans out as it attaches distally.
So again, really important to make sure you scan medially
to laterally and make sure you cover that entire
distal attachment portion.

Lateral Knee

So on we go laterally.
Now at the level of the knee joint itself,
you see proximal up this way,
distal down this way, proximal tibia in the middle,
just here again, being very wary of anisotropy, you'll see
an echogenic triangle just here if we can make that out.
And that's the lateral meniscus, that's the padding
of the joint laterally.
It's quite a common place particularly in athletes
to get tearing along there.
We can really zoom up on that meniscus here,
covering this entire portion here.
Again, you can approach this from posterolaterally.
Some people have quite a bit
of success with that approach.
I find that the straight
lateral approach is quite effective.
Also, the other trick you can use for looking at menisci in the knee is the chroma map.
The eye is a little more sensitive to shades
of color than it is to shades of black and white.
And so small little meniscal tears that come
through here, which are gonna appear
as hypoechoic fissures in this echogenic structure.
Sometimes they show up a lot clearer using the chroma.
So that's just a little trick to keep in mind.
Okay, again, having a look now further afield
and assessing the entire lateral knee complex,
again using the entire range of the transducer.
Five centimeters I believe it is lying
above the lateral meniscus.
You see the lateral collateral ligament sits just above.
Again, you're assessing that for integrity,
making sure it's intact.
Above that you're seeing the iliotibial band again,
this is a really long structure
that attaches distally here at the knee joint
but extends all the way up
and attaches onto the hip, in fact.
So whenever you're assessing the iliotibial band,
be really cognizant of patient history
and make sure that you
ascertain from the patient whether it's a distal iliotibial
band problem or a more proximal iliotibial band
issue right up by the hip.
So make sure that you get as much information out
of our patients as we possibly can.
You can see popliteus tendon down here.
Again, it's quite round, quite
echogenic quite normal looking in
this model, which is lovely.
And again, I'm just assessing generally for fluid
extending out of that joint.

Medial Knee

Alright, on we go medially
covering you in goo.
Typical sonographer.
Yeah, again, looks similar to the lateral side.
The medial meniscus can appear a little,
wider, top to bottom.
That's normal. It's not a sign of
widening of the joint at all.
That's just the normal anatomical structure.
Again, quite an echogenic, medial meniscus.
Now again, you're looking for continuity.
You're looking for any sort
of fissuring going down through here.
Or any sort of bulging is the other thing you
can get from the meniscus.
Sometimes the meniscus will wanna come right up and above.
The bony structures of the knee are budding
the subq fascia here.
And that's something that's considered abnormal.
Again, be sure to really zoom in
on a meniscus as much as you need to.
Using the HD zoom is ideal.
And again, be aware that the chroma is something that may,
that may help you in your assessment of the meniscus.
And again, you can look from posteromedially at the meniscus
if there's a particular area, particularly deep down sort
of deep to bone here.
If that's sort of a structure that's something
that's of particular interest clinically,
then certainly you can roll the patient slightly onto their
side and approach from more posteriorly.
But again, I find this medial approach is
quite effective in most patients.
Again, a little easier to see I think,
on the medial side than on the lateral side
is the medial collateral ligament.
Can see.
Again, let just make that a little bigger. Okay.
Be a good sonographer and bring my focus
up to where it needs to be.
Okay, so you can see here a number of
linear fibers running across here.
Again, attaching more proximally.
That's the medial collateral ligament.
It's the paired structure, again
with the lateral collateral ligament on the other side.
But again, it should appear nice and thin, nice and taut.
Again, you'll notice the knee is slightly flexed
for this procedure.
So that's certainly something to be aware of.
They're the major components that we look for
in the knee anteriorly.
The other thing that we can do,
depending on patient's symptoms
and indications is to look posteriorly in the knee.
Most people when they talk about musculoskeletal
ultrasound, one of the first thing that comes to mind is
a baker cyst.
And certainly that's something we're gonna find posteriorly,
posteriorly in the knee, in the popliteal fossa.

Posterior Knee

So, if I could just ask you
to roll up onto your side slightly facing that way.
Perfect. Again, if the patient's difficult to
move around, it's perfectly fine
to attack this from the side.
Again, you're gonna get a better overview if you
can get the patient prone.
So that's just something to be aware of. So posteriorly, now
again, tibia fibula deep, the deep structures
that you see, you can see the popliteal
artery pulsing away.
Again, just as a sort of corollary to your study,
it's a good idea just to scan through that small portion
of the popliteal artery.
Again, you can assess using color doppler,
power doppler also, if that's something that you prefer,
you can see the artery
pulsing and the vein next door.
So just extending your study a little bit further,
giving the radiologists a little bit more information.
You can assess the popliteal artery, certainly for aneurysm,
certainly for any plaque.
And again the vein, certainly looking for any thrombosis.
And making sure obviously that the vein is
easily compressible as part
of your deep venous thrombosis study
that most sonographers would be familiar with.
So again, a baker cyst is gonna appear
medially in the popliteal fossa.
It's going to lie between the semimembranosus
and the medial gastroc muscles at the back here.
So between these two guys,
our patient here doesn't have a baker cyst,
which is a good thing, but
you can see it would rise from this portion
of the popliteal fossa
and surround the medial gastroc muscle distally.
And again, more distally.
You can extend your study if the patient certainly has pain
that extends down in this area down into the
proximal calf region.
You can see here this is where the short saphenous vein will
sit again, you can extend your study to be looking
for thrombosis in that.
Medially we have the medial gastroc muscle,
this big powerful calf muscle at the back.
It has a paired structure on the other side.
Again, it should appear about symmetrical.
This is the lateral gastroc muscle
and then the soleus underneath.
So that's a trio of muscles at the back there, just
to be familiar with.
Again, just scanning through,
making sure everything looks homogenous.
The veins contained within the muscle
that you can see compressing there are easily compressible.
That's another cause of calf pain is
thrombosis in the muscular veins,
not necessarily the deep veins.
So it's important to cover that also.
But again, you can see how lovely
and homogenous these muscles are.
There's no areas of increased signal, no areas
of edema that would indicate, or the other way.
When a muscle starts to atrophy
and lose its bulk something to be aware of.
And that's our basic knee exam.