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OCD In the Knee, LAME

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Continuing on with our discussion on

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osteochondral lesions, it just would not be

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complete without talking about the most classic

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form of osteochondral lesion, which happens

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around the knee in the pediatric population.

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Most specifically, it happens at the lateral

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aspect of the medial femoral condyle.

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So, let's find the fibula; that's lateral.

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So we know this is the medial femoral condyle,

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and if you notice, this is at the lateral

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aspect of the medial femoral condyle.

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So, you know the term LAME, L-A-M-E, which

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stands for Lateral Aspect Medial; you

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know, E is for epicondyle, but medial condyle.

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So, this is where you have the most

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common location of an osteochondral

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lesion in the pediatric population.

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When we talk about osteochondral

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lesions, we have to characterize them.

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It's not just enough that

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we say that it's there.

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We have to talk about the size

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of the osteochondral lesion.

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So, you have to measure the osteochondral lesion.

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So, let's go ahead and do that.

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On the coronal view, if I go from here

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to here, it's about 2 centimeters.

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On the sagittal projection, if I go

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from here to here, it's also about 1.4 centimeters.

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4 centimeters.

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So we've given the sizes.

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Now we have to talk about its characteristics.

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This image on your left is a sagittal

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fat-suppressed fluid-sensitive sequence.

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We notice, I'm going to get rid of this line

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just so we can see things a little easier.

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You notice there's a rim of bright signal,

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a rim of low signal, and some

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more edema underneath that.

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We can also talk about the

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integrity of the cartilage.

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You know, there's a little bit of high

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signal on the undersurface of the cartilage.

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Okay.

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And this rim of signal here is not quite

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as bright as the fluid in the joint.

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So that also tells us about

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instability or stability.

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If we have fluid signal around this

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area of osteochondral lesion, that's

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as bright as the fluid in the joint.

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Okay.

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Then that indicates an unstable lesion.

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If it's just merely edematous

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like this, it's still stable.

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The thing to realize is, in the

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adolescent period,

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osteochondral lesions are a lot more

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resilient than in the adult population.

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In the adult population, a rim of edema

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alone would qualify it as an unstable lesion.

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But in the pediatric population, you

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really need fluid signal to be unstable.

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So this is not unstable.

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Right, by that criterion.

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We also look to see if there are any cystic

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changes around the osteochondral lesions.

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This one does not have any cystic changes.

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If an individual cyst is more than five

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millimeters, or there are multiple

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cysts, then that also means it's unstable.

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And finally, we look at the

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integrity of the cartilage.

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If the cartilage has rifts or tears

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in it, that indicates instability.

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So, looking at all those findings, I would say

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that this is a stable osteochondral lesion.

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They will go in and maybe fix it

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by drilling, or they may just rest

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the knee to see if it gets better.

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In the pediatric population, oftentimes

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you'll have areas of abnormal or what

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looks like abnormal fragmentation at the

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posterior aspect of the femoral condyle.

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And that should not be confused

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with an osteochondral lesion.

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First, those lesions occur on non

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weight-bearing surfaces, like over here.

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And second, there's no associated edema.

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So don't confuse something that happens

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back here with something that happens

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down here for an osteochondral lesion.

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And typically, these lesions here happen in

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a younger population, maybe 4, 5, 6, 7, or 8.

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This over here typically

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happens in an older population.

Report

Faculty

Mahesh Thapa, MD, MEd, FAAP

Division Chief of Musculoskeletal Imaging, and Director of Diagnostic Imaging Professor

Seattle Children's & University of Washington

Tags

Trauma

Pediatrics

Non-infectious Inflammatory

Musculoskeletal (MSK)

MRI

Acquired/Developmental

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