0:01

Our next section is lower extremity focused on the knee.

0:05

So when we think about knee radiography,

0:06

there are multiple X-ray views

0:08

or x-ray projections

0:09

that may be used in the routine setting.

0:11

We'll typically have a frontal projection done

0:13

as an anter posterior, a lateral projection,

0:17

and then a patella view which has a variety

0:20

of different names, often called a

0:22

merchant or a sunrise view.

0:24

If possible, it's preferred to do these projection standing

0:28

because that gives you insight into the load bearing

0:31

and whether there's potential joint space narrowing.

0:34

However, often within the emergency department, if

0:36

that knee is affected

0:38

or painful, it may be done in the supine position.

0:42

Other x-ray views that augment the routine is a PA flexed

0:46

or so-called tunnel view.

0:48

It helps for looking at arthrosis along the posterior aspect

0:52

of the joint and for helping

0:54

to identify intraarticular mineralized bodies.

0:57

Additional views may be augmented with oblique projections

1:01

and then across table lateral for severe trauma.

1:06

So here is our typical X-ray projections.

1:08

Sometimes only the affected knee is captured on the frontal.

1:12

Sometimes both knees are captured in order to compare left

1:16

to right and then the lateral is done in a semi flexed

1:20

position when it's load bearing.

1:23

Here's our patella view done with the knee flexed

1:27

and so it may be called a merchant view or a sunrise view.

1:30

In any case, once the knee is flexed beyond about 10

1:33

to 30 degrees, it should be engaged within the

1:36

trochlea sulcus.

1:38

So for any of these patella reviews that are performed,

1:43

you should have congruence between the medial facet

1:47

and the medial trochlea lateral

1:49

facet and the lateral trochlea.

1:52

So when the knee X-rays standing,

1:55

as we see on the left here, we prefer

1:57

to have a little bit of knee flexion.

1:59

When it's a cross table lateral, we may not get

2:02

as much knee flexion depending on the condition

2:04

and particularly if someone has a joint effusion.

2:07

So we're gonna talk more about joint effusions shortly,

2:10

but in this case we can see the person has a sup patellar

2:13

joint effusion that's noted in front of the femur

2:17

and behind the quadriceps.

2:19

So here are our knee typical radiographic projections

2:22

that are done, again, frontal

2:24

and lateral lateral in that semi flex position.

2:27

If it's load bearing, we can tell

2:29

by the imaging markers here

2:30

where the beads are in a dependent position

2:33

that this lateral was performed standing.

2:37

So what are part of our anatomy by expectation

2:40

and checklist for knee radiographs?

2:43

So as we go from top down on the frontal projection,

2:48

we can see the distal femur.

2:50

There's a lateral epicondyle

2:53

and condyle, which uh, condyle forms the articular surface.

2:57

We have a medial epicondyle and condyle.

3:01

The patella is gonna be projected over near the center

3:05

of the knee, a little bit above the joint line.

3:07

Typically within the intercondylar notch we have these

3:12

tibial spines here in

3:13

between maybe called the intercondylar eminence.

3:17

The fibular head will typically partly overlap over the

3:21

tibia and then we have the fibular shaft or diaphysis here

3:26

and tibia bone here as a larger structure.

3:30

On the lateral projection, again, we come down

3:33

for the distal diaphysis of the femur.

3:35

There is a little tubercle here for some of the adductors

3:39

and other attachments, uh,

3:41

which can sometimes be a little bit prominent.

3:44

The condyles will uh, not necessarily be overlapped

3:48

because of differences in position.

3:51

And so one condyle will be projected further out

3:54

than the other condyle.

3:56

The articular surface should be smooth.

3:59

We'll see the tibial spines here

4:01

with intercondylar tubercle.

4:03

The tibial plateau usually presents as a nice cortical line

4:08

that's intact as we see it in tangent to the X-ray beam.

4:12

The condyles are what help form the plateau.

4:15

Tibial tuberosity is where the patella tendon attaches.

4:19

And then we have our proximal tibia and fibula.

4:23

The patella is gonna be located over

4:26

the region of the trochlea.

4:28

So to emphasize with knee x-ray technique

4:31

often apply several different views

4:33

or projections used in evaluating the knee each

4:36

to give us a little bit different perspective

4:37

for the different pieces of anatomy

4:40

and potentially insight into alignment.

4:43

So there'll be a frontal or ap, a lateral tunnel.

4:48

PA flexion, which is typically done

4:50

with the knee bent about 30 degrees merchant

4:53

or sunrise are two ways of obtaining

4:56

that patella femoral articulation.

4:59

And then we may have it augmented with oblique projections,

5:02

although nowadays if there really is a question, oftentimes

5:05

CT is used to, uh, help characterize

5:09

or clarify findings on the initial x-ray findings.

5:14

So to recap, here's our

5:16

AP projection Following the bone contours,

5:19

there should be a smooth cortical line

5:22

that goes across all of the margins here.

5:25

Patella's projected to be above the femoral tibial joints.

5:29

So the femoral tibial joints are seen here

5:32

with the joint space represented

5:34

by articular cartilage and meniscus.

5:37

In the case of the knee, there is a tibial spine here,

5:41

one on the medial side that then defines the medial margin

5:45

of that medial more tibial compartment.

5:48

So this part is covered by cartilage, articular cartilage.

5:51

In the center we have absence of the cartilage,

5:54

but we have the cruciate ligaments

5:56

that reside in in this location.

5:58

Our lateral tibial spine then forms the articular surface

6:02

for the lateral compartment.

6:04

So this is our lateral for more tibial compartment.

6:07

And then fibular head will be overlapped somewhat

6:10

with the tibia here on the lateral projection, again

6:15

following the femoral cortex down as it enlarges

6:20

into the metaphysis.

6:22

And then the epiphysis, which all forms the condyles.

6:26

Again, not perfectly projected over each other.

6:29

Typically the medial is a little bit bigger,

6:32

so it may be projected a little bit

6:34

further out than the lateral.

6:36

And then posterior cortex here

6:39

and the femoral cortex can be quite thick.

6:42

Tibial plateau, so nice straight line, uh,

6:45

without interruptions or depression.

6:47

In the front is our tibial tubercle without irregularities.

6:50

So nice cortical margin.

6:53

Weak can see the infra patella fat pad here, so

6:57

that's fairly lucid.

6:58

The patella tendon, pre patella soft tissues.

7:02

And then the area

7:03

above the patella in this superior recess is often the area

7:07

where we look for effusions.

7:09

General working criteria are

7:11

that it fits less than five millimeters.

7:13

It's considered normal if it's five to 10 millimeters,

7:17

maybe indeterminate or small effusion

7:19

and greater than 10 is large.

7:21

But even just looking at it qualitatively

7:24

is probably sufficient for diagnosing uh, substantial

7:28

or clinically significant infusions.

7:31

So not routinely necessarily done in the emergency

7:33

department, but other reviews can be the PA flexed view

7:37

where if you're trying to look for more of arthritis

7:39

or more joint space narrowing along

7:41

those posterior compartments.

7:43

This also does give you a view into the tunnel so that in

7:46

that intercondylar notch,

7:48

which is why this is sometimes called a tunnel view,

7:51

this can then tell you if there's any bodies

7:53

or potentially other objects in there.

7:56

Here's an example of somebody with arthritis

7:59

where now we can see marked narrowing

8:01

of both media FOMO tibial compartments bilaterally.

8:04

On that flex projection here in our patella femoral

8:08

projection, we can see

8:10

that their patella is not completely congruent.

8:13

So there's a little bit of lateral tilting on both sides

8:17

that occurs in a number of individuals

8:19

and may predispose to patella femoral issues, uh, either

8:23

with a dislocation or arthritis.

8:27

And then finally, we may do oblique projections to kind

8:30

of better characterize what's going on either within each

8:33

form tibial compartment or tibial plateau.

8:36

So part of our knee X-rays, we look at the bones, femur,

8:39

tibia, fibula patella.

8:41

Some people have an extra bone known as a fea,

8:44

help identify if there's fractures, potential tumors,

8:48

or of a perioral reaction.

8:50

In the soft tissues, we can identify superficial bursa that

8:54

May be be soft tissue prominences,

8:56

potential meniscus pathology.

8:58

If there's joint space narrowing

9:00

or chondro calcinosis that's displaced joint effusions.

9:05

The muscles and tendons we don't see directly,

9:07

but sometimes can infer

9:09

by either increased opacity or thickening.

9:12

And with regards to the joints, if done as a load-bearing

9:15

technique, the joint space

9:17

and alignment are additional diagnoses that we can make.