Partial Tears

For Medical Students

What It Shows

A partial tear is a cruciate ligament with some fibres torn and some intact, so the ligament is neither normal nor absent. 5.7.1 covers the normal cruciate.

The two bundles tear separately, and a tear of one with the other intact is the usual anatomical basis for the term. 2.7.8 covers the anteromedial bundle.

It matters because the appearance overlaps with normal striation at one end and with a complete tear at the other, so the diagnosis sits in the gap between two things read reliably. 5.7.3 covers the complete tears.

How It Is Acquired

Assess continuity bundle by bundle rather than for the ligament as a whole, which needs the oblique and axial images. 5.5.9 covers the ligaments.

Check the line of the remaining fibres against the notch roof, because partially torn fibres often keep a normal line. 2.7.12 covers the surgical anatomy.

Look at the secondary signs, since they are what separates an injured ligament from a degenerate one. 5.11.7 covers bone marrow lesions.

Use a fluid sensitive sequence for the oedema and an intermediate weighted one for the fibres, because the two questions need different contrast. 5.2.16 covers fat suppression.

Compare with the posterior cruciate for buckling, which is a translation sign rather than a ligament sign. 5.8.1 covers the normal posterior cruciate.

What Abnormal Looks Like

Fibres that are continuous in part of the ligament and absent in another part, best seen where the bundles separate.

Increased signal within the ligament with some dark fibres preserved through it.

A ligament of normal line and abnormal substance, which is the appearance that makes the call difficult. 5.7.1 covers the normal cruciate.

Secondary signs of injury that are present but less marked than in a complete tear. 5.11.7 covers bone marrow lesions.

MRCS Level

How It Is Acquired

In a viva the expected answer says this is the least reproducible call in cruciate imaging and gives the reason before the technique.

The expected points are the bundle by bundle assessment, the oblique and axial images, the line, the secondary signs, and the comparison with examination.

Say that you would correlate with the examination rather than treating the report as the answer. 4.10.4 covers the Lachman test.

Say that the term covers a spectrum rather than a single lesion. 5.21.2 covers the cruciate imaging literature.

Say that the functional question is whether the knee is stable, which the image does not answer. 3.7.8 covers anterior stability.

What Abnormal Looks Like

The reasoning expected is that the bundles have different lengths and tighten at different angles, so one can fail at a load the other survives. 3.7.4 covers the bundle function.

The anteromedial bundle is the one tested by a Lachman examination, so an isolated posterolateral tear can leave a near normal anterior examination with a rotational complaint. 3.7.7 covers rotational stability.

Intact fibres under tension keep the ligament's line, which is why a partial tear loses the line sign that makes a complete tear easy. 5.7.3 covers the complete tears.

Partial tears can progress, and the imaging cannot say which will, so the decision rests on the examination and the activity rather than the appearance. 6.1.4 covers the natural history.

How Good It Is

This is the diagnosis magnetic resonance imaging makes least consistently in the cruciate ligament.

Its best contribution is the bundle level description, which tells a surgeon which part of the ligament is involved when it tells them nothing else. 2.7.9 covers the posterolateral bundle.

It is limited by the overlap with normal striation, by the absence of a definition, and by the fact that function rather than fibre count is the question. 5.7.1 covers the normal cruciate.

No figures appear for accuracy on this page, under decision 028, and the comparison is the claim: partial tears are called less consistently than either normal or complete ligaments, which is a comparison rather than a number.

FRCS Level

How Good It Is

At decision level a reported partial tear is a prompt to examine rather than a diagnosis to treat.

A partial tear with a negative pivot shift and no functional instability is managed on the examination, and the report changes nothing. 4.10.6 covers the pivot shift test.

A partial tear with a positive pivot shift is a functionally complete ligament whatever the fibres look like, and the examination wins. 3.7.9 covers the pivot shift mechanics.

A partial tear in a skeletally immature patient is a different decision because the alternative carries a physeal risk. 5.15.5 covers paediatric cruciate injury.

An examination under anaesthesia resolves the disagreement that imaging created, and is the appropriate next step rather than a repeat scan. 4.10.10 covers the examination under anaesthesia.

Where It Misleads

The commonest error is reporting normal bundle striation as a partial tear. 5.7.1 covers the normal cruciate.

Mucoid degeneration is reported as a partial tear, which sends a patient with no instability towards a reconstruction. 5.7.6 covers mucoid degeneration.

A partial tear is read as a reason to operate, when the examination is the indication. 4.10.3 covers chronic cruciate deficiency.

A near complete tear with a preserved line is reported as partial, understating it. 5.7.3 covers the complete tears.

The term is used without saying which bundle, which removes the only useful content. 5.20.3 covers reporting cruciate injuries.

Fellowship Level

Where It Misleads

At fellowship level the partial cruciate tear is the clearest instance in this chapter of a diagnosis that exists in reports and barely exists as an entity.

There is no agreed definition of how much fibre loss makes a tear partial, so two readers describing the same ligament use different words for it. 5.21.2 covers the cruciate imaging literature.

The published series disagree on whether partial tears progress, in part because they are not describing the same lesion. 6.1.4 covers the natural history.

Function is the question and fibre continuity is the measurement, and the relationship between the two is weak in exactly the middle range where the term is used. 3.7.8 covers anterior stability.

Oblique sequences improve bundle level assessment and are not in most standard protocols, so the information that would make the term useful is usually not acquired. 5.5.2 covers the sports knee protocol.

A partial tear reported in a knee that is clinically stable starts a pathway of further imaging and review that the finding does not support, which is a harm rather than an inconvenience. 5.1.6 covers imaging pitfalls.