The Posteromedial Corner: Oblique Popliteal Ligament
HIDEInteractive Transcript
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Knee anatomy on MRI posteromedial corner.
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Now it's time for the OPL, or oblique popliteal ligament.
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Let's take our diagram.
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We're looking from the back now, so this would be medial.
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There's the tibia, so that's lateral. The knee is slightly
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oblique, so this would be more to the front and this would be more to the back.
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We know this because the POL is going to be behind the middle layer of the MCL.
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And there may be a little cleft
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of separation between the two.
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But as we move back now, the semimembranosus makes
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a posteromedial corner contribution to the posterior capsule.
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And this is known as the extension
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to the oblique popliteal ligament.
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Now, the OPL, or oblique popliteal ligament
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arises from the capsular arm of the POL
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and this lateral expansion of the semimembranosus.
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So it receives some contribution
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from the POL, which we didn't really draw in here, but its main contribution is
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from the semimembranosus posterior reflection.
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And it has a course,
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posterior and somewhat superior, sweeping in a wide sheet across the back.
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Now look how far back it goes, the OPL.
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It goes so far laterally that it actually
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attaches to the osseous or cartilaginous fabella on the lateral side of the knee.
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It also attaches to the menisco-femoral,
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posterolateral joint capsule and to the plantaris muscle.
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So this structure, which starts on the medial side,
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has a contribution to posterior and posterolateral stability.
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And this is somewhat counterintuitive.
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The OPL also has a fibrous attachment
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to the lateral aspect of the PCL and it has a supporting role in the
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posteromedial, as well as the posterolateral corner.
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As stated previously, it's a very thin structure,
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so you'll see a sheet going across, but you're not going to be able
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to separate out the capsule from the OPL, so you're not going to see it very often.
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Now, the function of the OPL.
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Well, let's go back to the POL for a minute.
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The posterior oblique ligament,
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that is a secondary stabilizer of tibial translation.
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It also participates in internal and external rotation.
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But the OPL is a primary restraint,
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here's the OPL, it's a primary restraint to knee hyperextension.
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So if you lose this and your
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knee is going to overextend and the knee
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is going to look somewhat like this, it's going to be bowed in the middle.
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This is known as genu recurvatum.
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So don't confuse the OPL in the back with the POL in the front.
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These are two important structures that help support the posteral medial corner.
Stephen J Pomeranz, MD
Chief Medical Officer, ProScan Imaging. Founder, MRI Online
ProScan Imaging
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