Relationships Between the Joints of the Knee
HIDEInteractive Transcript
0:01
Knee anatomy.
0:03
Basic MRI.
0:06
Let's talk about the skeleton.
0:08
We've got the patella, which has extreme variability.
0:12
The perfect patella fits very nicely into the femur or trochlea.
0:18
It's got a lateral facet covered by cartilage.
0:21
It's got an apex and it's got a slightly undulated medial facet.
0:27
The medial and lateral facet are almost the same size.
0:30
The medial facet may be a little bit shorter in this direction than the lateral
0:35
facet, and that's okay, but it shouldn't be terribly shorter.
0:39
In other words, it shouldn't look like this.
0:43
That's a variation known as the Wiberg three
0:46
variation of patella and is a risk factor for this location.
0:51
More on that when we talk about the patella.
0:53
Then we've got an area of the patella that is uncovered.
0:56
In other words, there's no cartilage covering it.
0:59
That's the odd patellar facet.
1:01
In front of the patella is the prepatellar plate.
1:04
It is critical that you analyze not only
1:07
the size of the patella, too small, pebble patella, too big, patella magna,
1:12
the size of the facets. But more importantly, the shape and relationship
1:17
of this structure and its conformity to the trochlea of the femur.
1:22
In other words, how do these fit together?
1:24
Do they fit together like a jigsaw puzzle?
1:27
Is this deep enough or is it too shallow?
1:31
Is this too big for the structure that's meant to hold it?
1:35
So one of your jobs is to analyze
1:38
the relationships between bones, not just the bone itself.
1:43
Let's look at another area where relationships really matter.
1:46
In fact, relationships matter in everything.
1:48
But here's our femur and our tibia.
1:51
The femorotibial conformity, an alignment.
1:54
In other words, does the femoral condyle sit properly along the vertical axis
2:00
of the tibia or is it drifting over as occurs in osteoarthritis?
2:04
Does the curvature of the femoral condyle fit in the concavity of the tibia?
2:11
Does it accommodate it or is it flattened?
2:14
Sometimes you'll even see dysplasias of the femur.
2:17
One example would be discoid meniscus where the femoral condyle is flattened
2:22
and sometimes the fibular head is overgrown or hypertrophy,
2:26
as part of the anomaly.
2:28
You should be looking at the tibial notch,
2:32
whether it's too big or too small,
2:35
for notch dysplasia can be a cause of ACL deficiency and or insufficiency.
2:43
And then back to the fibular head again.
2:45
Not too many abnormalities or anomalies of the fibular head.
2:50
But we said that the fibular head can be big in patients with discoid meniscus.
2:55
There's also an accessory bone, which this patient does not have, called the fabella.
3:00
It is located in a tendinous structure and it will get its own vignette.
3:05
It is located posteriorly. Conformity, the relationship of one bone to another.
3:13
Bone-size dysplasias,
3:16
such as that occurring in the patella or the femoral notch of the knee. These are all
3:21
relevant in assessing the basic skeletal anatomy of the knee.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
© 2025 Medality. All Rights Reserved.