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Complete Tears

Page 5.7.3 · ACL MRI · imaging page

The completely torn cruciate ligament, read with the secondary signs rather than from the ligament alone.

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The same topic at 4 depths

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Complete Tears

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For Medical Students

What It Shows

A complete tear is a cruciate ligament with no intact fibres bridging from femur to tibia, so the restraint is gone. 3.7.8 covers anterior stability.

The ligament is usually visible as retracted or wavy fibres with fluid in the gap rather than as nothing at all. 5.7.1 covers the normal cruciate.

It matters because this is the one state of the ligament that imaging and examination agree about, which makes the secondary signs useful rather than necessary. 4.10.4 covers the Lachman test.

How It Is Acquired

Look for discontinuity on the sagittal images through the notch, then confirm on the coronal and axial planes. 5.5.9 covers the ligaments.

Assess the line of any remaining fibres, because a flat ligament lying below the notch roof is the line sign. 2.7.12 covers the surgical anatomy.

Measure anterior tibial translation against the femoral condyles, which is a mechanical consequence rather than a ligament appearance. 3.7.8 covers anterior stability.

Look at the lateral femoral condyle and the posterolateral tibia for marrow signal, which records the impaction of the injury. 5.11.7 covers bone marrow lesions.

Look for the associated injuries deliberately: the posteromedial meniscocapsular junction, the meniscal roots, the anterolateral structures and the collaterals. 5.6.10 covers ramp lesions.

What Abnormal Looks Like

An absent or discontinuous ligament with fluid signal filling the expected course.

Retracted wavy fibres, which is the torn ligament rather than an empty notch.

Anterior translation of the tibia relative to the femur, with a buckled posterior cruciate as its companion sign. 5.8.1 covers the normal posterior cruciate.

Marrow signal in the lateral femoral condyle and the posterolateral tibia, and a deepened lateral femoral notch. 5.11.7 covers bone marrow lesions.

Key Learning Points

  • A complete tear has no fibres bridging femur to tibia.
  • The torn ligament is usually visible as retracted wavy fibres.
  • The line sign is a mechanical observation rather than a signal one.
  • Anterior translation and a buckled posterior cruciate are companion signs.
  • The associated injuries are looked for deliberately rather than noticed.

MRCS Level

How It Is Acquired

In a viva this is the study where the expected answer moves quickly past the ligament to the rest of the knee.

The expected points are the discontinuity, the line, the translation, the marrow signal, and the deliberate search for associated injuries.

Say that you would report the meniscal roots, the posteromedial corner and the anterolateral structures as part of the same study. 5.6.9 covers root tears.

Say that the marrow signal records the mechanism as well as the injury. 3.7.14 covers the injury mechanisms.

Say that the secondary signs let you call a tear when the ligament itself is equivocal. 5.7.2 covers the partial tears.

What Abnormal Looks Like

The reasoning expected is that losing the ligament lets the tibia translate forwards, so the translation and the buckled posterior cruciate are measurements of the mechanical state rather than appearances of the lesion. 3.7.8 covers anterior stability.

The lateral femoral condyle impacts the posterolateral tibia during the pivoting injury, which is why the marrow signal sits in that pair of locations. 3.7.14 covers the injury mechanisms.

A deepened lateral femoral notch is the bony record of the same impaction and persists after the oedema has gone, which makes it useful late. 5.3.14 covers avulsion injuries.

The associated injuries matter more than the cruciate for the operation, because the cruciate will be reconstructed either way and the meniscus and corners change the plan. 5.6.10 covers ramp lesions.

How Good It Is

The complete cruciate tear is the finding magnetic resonance imaging calls most reliably in this chapter.

Its best contribution is the associated injuries, which are the part of the study that changes an operation. 5.6.9 covers root tears.

It is limited by the equivocal acute knee full of blood, where oedema obscures the ligament and the secondary signs carry the reading. 6.2.5 covers the acute haemarthrosis.

No figures appear for accuracy on this page, under decision 028, and the comparison is the claim: the complete tear is read more reliably than the partial tear, which is a comparison rather than a number.

Key Learning Points

  • Losing the ligament lets the tibia translate, which the image measures.
  • The marrow signal pair records the pivoting impaction.
  • A deepened lateral femoral notch persists after the oedema resolves.
  • The associated injuries change the operation more than the cruciate does.
  • The secondary signs carry the equivocal acute study.

FRCS Level

How Good It Is

At decision level the cruciate tear is rarely the decision, and the study is read for everything around it.

A root tear or a ramp lesion alongside the cruciate tear changes the operation and is the reason the study is worth reading carefully. 5.6.9 covers root tears.

Anterolateral injury alongside the cruciate tear is part of the argument for an extra-articular procedure, which makes it a planning finding. 2.11.3 covers the anterolateral ligament.

A collateral or corner injury changes the timing as well as the operation. 5.9.2 covers medial collateral sprains.

A deepened lateral femoral notch in a knee presenting late is evidence of the original injury when the oedema has gone. 5.7.5 covers chronic cruciate injury.

Where It Misleads

The commonest error is stopping at the cruciate, so the findings that change the operation go unreported. 5.20.3 covers reporting cruciate injuries.

The posteromedial meniscocapsular junction is not inspected, and a ramp lesion is missed. 5.6.10 covers ramp lesions.

Marrow signal is reported as a bruise without the mechanism being read from it. 5.11.7 covers bone marrow lesions.

The acute haemarthrosis obscures the ligament and a tear is called indeterminate when the secondary signs settle it. 6.2.5 covers the acute haemarthrosis.

An empty notch is reported without the retracted fibres being sought, which loses the chance to describe the tear's level. 5.7.1 covers the normal cruciate.

Key Learning Points

  • Stopping at the cruciate loses the findings that change the operation.
  • The posteromedial corner goes uninspected and a ramp lesion is missed.
  • Marrow signal is reported without reading the mechanism from it.
  • The secondary signs settle a study the haemarthrosis obscures.
  • The level of the tear is lost when the retracted fibres are not sought.

Fellowship Level

Where It Misleads

At fellowship level the complete cruciate tear is the easy part of the study, and treating it as the finding is the error the whole chapter turns on.

The reconstruction happens on the examination and the patient, so the cruciate's appearance adds little to a decision already made. 4.10.6 covers the pivot shift test.

What the study can add is the associated injuries, and the ones that matter most are the ones detected worst: ramp lesions, root tears and anterolateral injury are all under-reported. 5.6.10 covers ramp lesions.

The tear's level matters for a repair or an augmentation approach and is often not described, because the report answers whether rather than where. 5.7.8 covers cruciate healing.

Anterior translation is measured on an unloaded supine study, so the mechanical quantity reported is not the one the patient experiences. 5.18.5 covers weight bearing imaging.

Reporting conventions here were set when the cruciate was the question, and the question has moved to everything around it without the report following. 5.20.1 covers structured reporting.

Key Learning Points

  • The reconstruction decision is made on examination, not appearance.
  • The associated injuries that matter most are detected worst.
  • The level of the tear is often not described.
  • Translation is measured unloaded and supine.
  • The reporting convention has not followed the question.

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.

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