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<v ->Let's turn our attention now to the knee

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and look at the bursa that are located about the knee.

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These are three in number,

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and I've labeled them for you 1, 2, and 3.

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Number 1 represents the location of the prepatellar bursa.

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Number 2 represents the location

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of the superficial infrapatellar bursa.

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And number 3 represents the location

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of the deep infrapatellar bursa.

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Bursitis may develop in one or more

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of these three particular sites.

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When we look at the anatomy of the prepatellar bursa,

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and again, Rodrigo did a nice study of this

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when he spent time with us,

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it is a layered structure

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and there are various segments of it.

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You can see that here in this histology,

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but they often communicate.

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So when we see bursal fluid

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in the prepatellar bursa is often uniform

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and although it may be separated by small thin septic.

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So that would be the location of prepatellar bursitis.

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To show you an example,

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here is one example of hemorrhagic bursitis.

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Now you can see when dealing with bursitis

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in the prepatellar location,

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the bursa sits pretty much atop the patella.

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Unfortunately for us,

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it may extend more to one side than to the other side.

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And the reason that is unfortunate,

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is because there's another condition

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involves this particular area

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that can lead to problems in differential diagnosis.

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And that is a Morel-Lavallee lesion.

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This is a lesion that is considered

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a degloving injury related to shearing force

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that separates fat from adjacent fascia.

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And it produces a mass filled with fluid lymphatic material,

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blood, and sometimes fat.

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Some of the cases are not as widespread

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as the four examples that I show you here.

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So you could imagine that in those locations

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and when not so profound,

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they may resemble the findings of prepatellar bursitis,

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but when they become this extensive

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and they sweep along the medial and lateral aspect

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of the knee, we know we're not dealing

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with prepatellar bursitis.

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Here's another example of one,

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this one, a bit eccentric.

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It has an homogeneous signal intensity,

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but you can see why this could cause problems

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in some cases with the differential of prepatellar bursitis.

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The second location of bursitis about the knee

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is the superficial infrapatellar bursa.

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And I can tell you I have not seen a lot of cases

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through the years of bursitis in this location,

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but I have seen a few cases where you have bursitis here,

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where the fluid actually also communicates

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with the prepatellar bursa.

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Here's an example of such a case.

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You can appreciate that this fluid extends

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from the level of the prepatellar bursa

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down to the area of the superficial infrapatellar bursa.

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That's been my experience with fewer cases

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of fluid localized to this particular area.

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The final bursa that occurs on the anterior aspect

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of the knee is the deep infrapatellar bursa.

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Near the anatomy is somewhat unique.

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This is half as a fat and as you know,

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there is a tag of fat that extends downward.

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It's often called an apron of fat.

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Here's what it looks like on when you study it

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with gross techniques in a cadaver you can appreciate it.

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So when you see deep infrapatellar bursitis,

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it's not uncommon to see tags of normal or abnormal fat

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extending down into the top of this particular bursa.

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That is one example.

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Sometimes that is not the case.

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And the deep infrapatellar bursa

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is more parasagittal than centrally located.

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It looks on in the coronal plane often like the letter H.

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So it's not unusual.

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You'll have one limb of the letter H distended

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maybe the transverse part will also be distended.

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And the other limb which will be over here

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will not contain fluid.

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In other cases,

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this will look like the full letter H

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typical of the deep infrapatellar bursa.

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One of the diseases that is associated

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with deep infrapatellar bursitis of course,

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is Osgood-Schlatter disease.

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The bone fragmentation is often associated with fluid

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and sometimes synovial proliferation within this bursa

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associated also often with tendon abnormalities

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including tendon thickening,

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and even tendon tears,

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and sometimes associated with failure

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on the opposite side of the tendon where it attaches

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to the apex of the patella,

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perhaps you know that Sinding-Larsen-Johansson disease.