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<v ->Now in some situations, we have a hemarthrosis,

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blood within a joint.

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Injury, hemophilia, other bleeding disorders.

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Pigmented villonodular synovitis,

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certain neoplasms like synovial hemangioma, for example.

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Neuropathic osteoarthropathy,

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a variety of crystal deposition disease,

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chronic renal disease, anticoagulant therapy,

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I mean, I can go on and on, there are a lot.

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Hemarthrosis is found within a joint.

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Within acute hemarthrosis in some cases,

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you will see a fluid level.

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Whenever you see fluid levels within a joint,

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take a moment, pause,

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try to figure out the signal intensity of the layers.

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Regardless, of course, you got to decide

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are you dealing with a lipohemarthrosis,

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or are you dealing with a hemarthrosis?

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Now, I'm gonna talk about lipohemarthrosis in a moment,

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but if you have a lipohemarthrosis,

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one of the layers ought to look like that.

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Here we have a hemarthrosis,

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you can see it's a fat suppressed image, right?

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But neither of these layers looks like fat.

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So this is not a lipohemarthrosis,

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this is a hemarthrosis, oh, this is an incredible case.

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See I have, I've got this from Rodrigo

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talking about how good these cases are.

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This is a great case.

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Here is a fracture of the intercondylar eminence

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of the of the tibia

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and that's an entrapped medial meniscus

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preventing reduction of that bone fragment.

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I'm not showing it for that, but it's terrific.

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But anyway, here you can see the fluid level.

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This is a hemarthrosis.

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Now once again, a nice article to know about is this one,

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which was published about five or six years ago.

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And what they did is they studied almost 1200 patients

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who had post-traumatic hemarthrosis of the knee,

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trying and where they had gotten an MRI

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are pretty quickly, within 8 days.

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And they tried to figure out what's the pathology

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that led to the hemarthrosis.

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Here I've summarized it, it was an ACL tear alone,

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or such a tear combined with meniscal or ligamentous injury

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over 50%.

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It was a meniscal tear alone or more commonly,

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an associated ligamentous injury, 40%.

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There was an MCL tear alone or combined again,

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with meniscal or ligamentous injury, that was almost 30%.

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Osteochondral fracture patellar dislocation.

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I want to make two more comments about it.

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If you have an immediate hemarthrosis with an ACL tear,

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it's probably not the ACL tear that produced it.

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You see the blood supply to the ACL when it's injured,

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it's like a dripping faucet,

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it takes time for fluid to accumulate.

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So if you have an ACL tear and there is a hemarthrosis,

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very quickly, there's usually an osteochondral fracture

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that accounts for the hemarthrosis.

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And the second is the point made

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at the very bottom of this slide, patellar dislocation

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was the most frequent cause of hemarthrosis

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in persons below the age of 16 years,

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that's shown at the top right image here,

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classic planting of the bone contusion and fracture

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associated with a lateral dislocation of the patella.

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You can see the femoral and changes on in the patella

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and you can appreciate retinacular injury

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and there is the hemarthrosis present,

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the black arrow indicating that.

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Now we come to a lipohemarthrosis.

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And with very few exceptions,

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when you identify a lipohemarthrosis

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there is a fracture present.

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Now, there are exceptions.

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The two exceptions I would emphasize are joints

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that have large intracapsular fat pads

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that by themselves can be injured.,

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so you can have lipohemarthrosis

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plus the elbow and the knee.

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But whenever you do see a lipohemarthrosis,

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spend time trying to find the fracture.

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A hyper acutely, it has been noted that bubbles of fat,

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one of the manifestations you're gonna see,

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and although not always, more commonly those bubbles

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arise and extend to the surface of the hemarthrosis.

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So that's where you want to look.

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In less common situations, they form within clots.

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And in those situations, the fat may be located

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below the surface of the hemarthrosis.

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The other pattern which you all know,

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is the layered pattern.

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We have in fact three layers, two levels.

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The upper layer now does conform

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to the signal intensity of fat, fat suppressed image.

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Here is the serum and below that, the cilia

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or an adequate effect of the blood.

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So that is the classic pattern.

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And in very rare instances you have both.

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So here we have the fluid levels

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and we have the bubbles of fat in one single example.

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But the important thing is clinically,

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is you wanna go ahead and and look

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for a fracture when you have a lipohemarthrosis.

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And when you're dealing with fractures about the wrist,

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in the hand, in the ankle belt, the foot,

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the fat may escape from the bone or rarely from the joint

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and end up within a tendon sheath.

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So this is tenosynovial fat,

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well shown here involving the dorsal extensor tendons

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and you can appreciate with the black

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or the side of the fracture involving the distal radius.

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Uncommonly, you will find blood clots within joints.

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Okay, here's an example,

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as you know, when you deal with blood clots and hemorrhage,

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you end up with variable signal intensity,

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but here you can see

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the rim of high signal on T 1-weighted

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and mixed signal on the intermediate weighted

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and gadolinium images, but this was a large blood clot.

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Pigmented villonodular synovitis,

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certainly is a cause of hemarthrosis,

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and now we turn to what do we see with chronic hemarthrosis?

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And of course, you all know the answer to this.

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We looked for hemosiderin deposition

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of low signal throughout,

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particularly on gradient echo imaging.

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This is an old case, it was one of the,

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I think it was the first case

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I saw of pigmented villonodular synovitis with MRI.

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The images are not that pretty

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but at least they do show you the hemosiderin deposition

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within the joint in the synovium

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here within the anterior interval of the knee,

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some within the bone

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and this hemosiderin-laden small popliteal cyst as well.

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So we always think of pigmented villonodular synovitis

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as one of the processes

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that will lead to hemosiderin deposition

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owing to the presence of chronic hemarthrosis.

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And I'll talk more about hemosiderin later

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and I'll talk more about

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pigmented villonodular synovitis as well.

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Hemophilia, you know we learn a lot about hemophilia,

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it's a clinical diagnosis.

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Sometimes the clinician knows it

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but doesn't share that knowledge with you

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on the request slip.

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We all know the basic facts about hemophilia,

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most commonly we see it in the knee,

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the ankle and in the elbow.

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Those are the three most common sites.

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But I liked this case,

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because this points out a fourth site.

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When you look for the changes of hemophilia about the ankle,

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it is not uncommon

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that two joints are involved, both weightbearing.

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One is the ankle joint,

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the other is the posterior subtalar joint.

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One of two subtalar joints,

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not three, but two subtalar joints.

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And indeed you can see in both of these joints

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hemosiderin deposition.

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Alright, so keep that in mind.

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In fact, I would tell you the combination

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of ankle and posterior subtalar joint involvement

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with nothing else, you always ought to consider hemophilia

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even if you haven't been given that information.

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And we had another rule that we used to use

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with conventional radiography.

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When you looked at the elbow and hemophilia

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you look for an enlarged liquid on fossa.

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Often that depression enlarge because of erosion.

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So look at this case, hemophilia involving the elbow.

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Look at the enlarged liquid on fossa,

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hemosiderin deposition everywhere, classic hemophilia.