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MR Imaging: Other Findings

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Now there are certain ligamentous

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and tenderness findings that may accompany an ACL there,

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they're kind of indirect findings In the normal

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situation in the extended knee,

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if you draw a line along the posterior aspect, you have

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to have two points to draw the line.

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But if you do so, the inferior aspect

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of the posterior cruciate,

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that line intersects the roof of the intercondylar notch.

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And you can see that here when you have a tear

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of the anterior cruciate ligament with anterior translation

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of the tibia, there is laxity

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of the posterior cruciate ligament.

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And if you draw a line along two points

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of the inferior aspect of the posterior cruciate,

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it does not intersect the roof of the intercon of notch.

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And here's an old example where you, I'm showing you

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that particular line being drawn, not intersecting, the roof

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of the inter colar notch.

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And then another thing that can be seen as an indirect sign

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of a complete tear

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of the anterior cruciate ligament is malalignment

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between the femur and tibia, or between the femur

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and meniscus, or between the meniscus

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and tibia, leading to a number of findings

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that have been described in the literature known

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as the uncovered lateral meniscus sign

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and the positive posterior femoral line sign.

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Let me tell you statistically, when you look at Mr images

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in many patients who have complete tears

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of the anterior cruciate ligament, that at the time

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of imaging there will be an offset,

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although it may not be a major offset of

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between the lateral femoral condyle

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and the lateral tibial plateau.

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And on the medial side, no offset is seen.

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That to me indicates of course, internal rotation

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of the tibia at the time of imaging

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and likely suggests that that was part of the mechanism

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of the anterior cruciate ligament tear.

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There are some abnormalities

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that can be seen in the infra patella fat pad

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as indirect signs of a tear of the anterior cruciate,

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a shearing injury with abnormal recesses in that,

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uh, fat pad.

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Half his fat pad have been described.

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And another thing you may see is injury involving the

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ligament of mucosa shown in this particular case

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where there's, uh, injury with edema about it as well

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as edema at one of its points of attachment on the patella.

Report

Faculty

Donald Resnick, MD

Professor Emeritus, Department of Radiology

University of California, San Diego

Mini N. Pathria, MD, FRCP(C)

Division Chief, Musculoskeletal Imaging

University of California San Diego

Eric Y. Chang, MD

Adjunct Professor, Radiology

University of California, San Diego

Brady K. Huang, MD

Clinical Professor of Radiology

UC San Diego Medical Center

Tags

Musculoskeletal (MSK)

MRI

Knee