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KneeSchool/Imaging Academy/Posteromedial Corner Injuries

Posteromedial Corner Injuries

Page 5.9.5 · Medial Knee MRI · imaging page

The combination that decides, and the point at which the medial side stops healing reliably.

Pipeline status. Editorial draft. Evidence verification did not run. Not consultant reviewed. Not for clinical use.

The same topic at 4 depths

Each tier deepens the one below it and never repeats it. Choose the level you want.

Posteromedial Corner Injuries

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For Medical Students

What It Shows

A posteromedial corner injury involves the posterior oblique ligament, the capsule, the semimembranosus attachments and the meniscocapsular junction together. 2.9.4 covers the posteromedial corner.

Magnetic resonance imaging shows them on posterior coronal and axial images. 5.5.2 covers the sports knee protocol.

It matters because the medial side heals reliably until this corner is involved. 5.9.2 covers MCL sprains.

How It Is Acquired

Use thin posterior coronal and axial images. 5.5.2 covers the sports knee protocol.

Assess each component and report it as intact, injured or not assessable. 5.20.4 covers reporting MCL injuries.

Assess the meniscocapsular junction specifically. 5.6.10 covers ramp lesions.

Assess the semimembranosus and its tibial attachments. 2.9.5 covers the semimembranosus.

Assess the cruciates, since this corner rarely fails alone. 3.9.10 covers the combined ACL and MCL injury.

What Normal Looks Like

Each posteromedial component identifiable and continuous. 2.9.4 covers the posteromedial corner.

An intact meniscocapsular junction. 5.6.10 covers ramp lesions.

Normal semimembranosus attachments. 2.9.5 covers the semimembranosus.

No posteromedial soft tissue oedema. 5.5.9 covers the ligaments.

What Abnormal Looks Like

Injury of two or more components, which is the pattern. 2.9.4 covers the posteromedial corner.

Posteromedial oedema with the components hard to separate. 5.5.9 covers the ligaments.

Meniscocapsular separation. 5.6.10 covers ramp lesions.

Avulsion at the semimembranosus attachment. 2.9.5 covers the semimembranosus.

An anterior cruciate tear alongside, which is the usual combination. 5.7.3 covers complete tears.

Key Learning Points

  • The injury is a combination of components.
  • The medial side heals reliably until this corner is involved.
  • Each component is reported separately.
  • The meniscocapsular junction is part of the corner.
  • The corner rarely fails alone.

MRCS Level

How It Is Acquired

In a viva the expected answer lists the components.

The expected points are the posterior images, each component, the meniscocapsular junction, the semimembranosus, and the cruciates.

Say that the grading is clinical and the imaging is structural. 4.12.1 covers the valgus stress testing.

Say that this corner carries rotation. 3.9.6 covers the posteromedial corner function.

Say that a missed corner injury is a recognised cause of cruciate graft failure. 5.7.11 covers the graft failure.

What Abnormal Looks Like

The reasoning expected is that these structures act together to resist valgus and internal rotation, so the deficit follows the combination rather than any single component. 3.9.6 covers the posteromedial corner function.

That is the same argument the lateral corner makes, and the two chapters reach it from opposite directions: laterally the structures are hard to see, medially they are easy to see and get merged. 5.10.3 covers PLC injuries.

Acute oedema establishes the pattern and obscures the parts. 5.5.9 covers the ligaments.

The meniscocapsular separation is the component with its own operation. 5.6.10 covers ramp lesions.

How Good It Is

Magnetic resonance imaging is the best available structural assessment of this corner and does not grade the laxity.

Its best contribution is the combination of components and the meniscocapsular junction. 5.6.10 covers ramp lesions.

It is limited because acute oedema merges the components, because chronic injury leaves nothing to see, and because the deficit is rotational and clinical. 4.12.6 covers the AMRI assessment.

No figures appear for accuracy on this page, under decision 028, and no laxity values or grading thresholds appear either: those are clinical grades with published definitions and this environment cannot check them.

Key Learning Points

  • The deficit follows the combination of components.
  • The lateral chapter reaches the same point from the other side.
  • Medially the structures are easy to see and get merged.
  • Acute oedema establishes the pattern and hides the parts.
  • The meniscocapsular separation has its own operation.

FRCS Level

How Good It Is

At decision level the imaging decides whether the corner is addressed alongside a cruciate reconstruction. 3.9.10 covers the combined ACL and MCL injury.

A posterior oblique injury with a meniscocapsular separation is the pattern that gets operated. 5.9.4 covers POL injuries.

Left untreated this corner loads the graft. 5.7.11 covers the graft failure.

A chronic corner injury with valgus alignment raises an osteotomy. 5.17.4 covers the osteotomy.

An examination under anaesthesia records what the imaging cannot. 4.12.6 covers the AMRI assessment.

Where It Misleads

The commonest error is reporting the superficial ligament and calling the medial side done. 5.9.2 covers MCL sprains.

Absence of a component from the report is read as that component being intact. 5.20.4 covers reporting MCL injuries.

A chronic injury with no oedema is read as normal. 5.5.9 covers the ligaments.

A semimembranosus avulsion is reported as a hamstring injury. 2.9.5 covers the semimembranosus.

Rotational laxity is inferred from the appearance. 4.12.6 covers the AMRI assessment.

Key Learning Points

  • Reporting the superficial ligament is not reporting the corner.
  • Absence from the report is not evidence of integrity.
  • A chronic injury with no oedema reads as normal.
  • A semimembranosus avulsion is misattributed.
  • Rotational laxity cannot be inferred.

Fellowship Level

Where It Misleads

At fellowship level the corner injury was missed and the reconstruction has stretched. 5.7.11 covers the graft failure.

The original study usually shows it, so obtaining and re-reading that study is the productive step. 5.20.1 covers structured reporting.

Chronic injury has no oedema and may have no identifiable components, so the diagnosis becomes clinical and the imaging supports the plan. 4.12.6 covers the AMRI assessment.

A reconstruction here carries no published expected appearance. 5.9.7 covers the post-operative medial reconstructions.

Valgus alignment in a chronic medial injury is part of the problem and part of the operation. 5.3.6 covers the long leg alignment films.

The useful report lists each component with its state, the meniscocapsular junction, the cruciates and the alignment. 5.20.4 covers reporting MCL injuries.

Key Learning Points

  • The original study usually shows what was missed.
  • Chronic injury may have no identifiable components.
  • A reconstruction has no published expected appearance.
  • Valgus alignment is part of the problem and the operation.
  • The report lists components with their state.

Explore Further

Where this topic came from and where it goes next in the spiral.

References

No reference list is attached to this draft. Evidence verification has not run, because source retrieval was unavailable at generation time. Under the Operations Handbook a missing reference is acceptable and an invented one is a critical failure, so nothing has been cited and no citation marker appears in the text. This page carries no diagnostic accuracy figure, which is decision 028 rather than an omission: the comparative standing of the modalities is standard teaching and a specific sensitivity written from memory is the same class of claim as an invented citation, so ACC-001 refuses the number and the page states the comparison. A reviewer with the literature can add the figures into How Good It Is without restructuring the page. Any measurement here, including a sequence parameter, an angle or a millimetre, is written from standard teaching, has not been checked, and is registered under decision 006 in pipeline/config/figures with a verification state of UNVERIFIED_FROM_MEMORY.

Safety. KneeSchool is educational and does not give individual medical advice. Seek urgent assessment for a knee that cannot bear weight after an injury, a hot swollen knee with a fever, or new numbness, weakness or coldness in the leg or foot.