Anterolateral Rotatory Instability

For Medical Students

What It Tests

Anterolateral rotatory instability is the lateral tibia rotating and subluxing forwards under load, which is the movement a patient describes as the knee giving way on a turn.

It requires the anterior cruciate to be deficient, and its size depends on the anterolateral structures: the iliotibial band's deep fibres, the Kaplan fibres and the anterolateral ligament. 3.11.3 covers the last of those.

Assessing it means grading the pivot shift rather than performing a separate test, because the pivot shift is the pattern made visible. 4.14.1 covers it.

How It Is Performed

Perform the Lachman test first, to establish that the anterior cruciate is deficient. 4.10.4 covers it.

Perform the pivot shift with the patient fully relaxed, grading the glide, the clunk and whether it is reproducible. 4.14.1 covers the grading.

Perform the Slocum test with the tibia internally rotated, which reads the same restraint at ninety degrees. 4.14.2 covers it.

Perform the dial test, because a posterolateral corner injury enlarges the pattern and changes the operation. 4.13.5 covers it.

Ask the patient to describe the movement that fails, since a rotational complaint is more specific than any of the tests. 4.2.6 covers giving way.

What a Positive Means

A large pivot shift in a knee with a deficient anterior cruciate indicates that the anterolateral structures are contributing little, which is what makes this a pattern rather than a single tear.

A small pivot shift in the same knee indicates the anterolateral structures are intact, and the instability is translational rather than rotational. 4.10.4 covers that reading.

A large pivot shift with an increased dial difference indicates a posterolateral corner injury as well, which is a different and larger problem. 4.13.4 covers it.

A lateral meniscal posterior horn tear enlarges the pattern mechanically, so a large shift should prompt a search for one. 4.9.9 covers root tears.

MRCS Level

How It Is Performed

In a viva this is the pattern to name when asked why some anterior cruciate reconstructions are augmented laterally, and that is almost always the question behind it.

The expected points are the Lachman test, the graded pivot shift, the Slocum test in internal rotation, the dial test, and the patient's description.

Say that the pivot shift grade is the assessment, and that there is no separate anterolateral test, because candidates invent one.

Say that the anterolateral structures are a complex rather than a single ligament, and that whether the anterolateral ligament is a discrete structure is contested. 3.11.9 covers the controversy.

Say that you would examine for a Segond fracture on the radiograph, since a lateral capsular avulsion is radiographic evidence of this injury. 3.11.6 covers the mechanics.

What a Positive Means

The reasoning expected is that internal rotation of the tibia is restrained by the anterior cruciate and by the anterolateral structures together, so the pattern's size depends on both. 3.11.5 covers internal rotation control.

The Kaplan fibres anchor the iliotibial band to the femur and contribute to that restraint, which is the anatomical basis for the deep lateral procedures. 3.11.2 covers their function.

The anterolateral ligament, where it is accepted as a structure, contributes to the same restraint, and the disagreement is about anatomy rather than about the mechanics. 3.11.3 covers its function.

The lateral meniscus posterior horn provides a bony block to the subluxation, so meniscal and ligamentous contributions add together. 4.9.10 covers meniscal deficiency.

How Good It Is

The assessment of this pattern is the pivot shift, so its reliability is the pivot shift's reliability, which is poor awake and good under anaesthesia. 4.14.6 covers that setting.

Nothing else reads the pattern. The Slocum test reads the same structures less sensitively and the dial test reads a different corner. 4.14.2 covers the Slocum test.

Imaging contributes a Segond fracture and an anterolateral ligament appearance, and neither tells you whether the knee is rotationally unstable. 4.1.6 covers that relationship.

The patient's history is the most sensitive assessment available, which is unusual and is the honest position. 4.2.2 covers instability as a symptom.

No figures appear for any accuracy comparison on this page, under decision 023, and the comparison is the claim being made.

FRCS Level

How Good It Is

At decision level this pattern decides whether a lateral extra-articular procedure is added to a cruciate reconstruction, and that is a live decision in current practice. 3.11.7 covers the procedure.

A high grade pivot shift is the main clinical argument for adding one, and it is strongest in a young pivoting athlete, in a revision, and in a knee with generalised hypermobility. 4.23.2 covers athletes.

The pattern also determines whether a lateral meniscal repair is part of the operation, since the posterior horn's contribution is mechanical and restorable. 4.9.9 covers root tears.

It does not decide whether to reconstruct, which remains a functional decision, and this chapter's argument is that the test which best matches the complaint still does not make that call. 4.10.3 covers the chronic knee.

Where the awake assessment is equivocal and the decision is real, examination under anaesthesia is how it is settled, and it should be arranged before the operating list rather than discovered on it. 4.14.6 covers it.

Where It Misleads

The commonest error is treating the pattern as a diagnosis of a named ligament rather than as a description of a movement.

The second is grading the pivot shift awake and treating the grade as reliable.

The third is attributing a large shift to the cruciate alone and missing a corner injury or a meniscal tear.

The fourth is adding a lateral procedure on a small shift, which adds stiffness and lateral pain the patient did not need. 4.2.4 covers stiffness.

The fifth is relying on an anterolateral ligament appearance on imaging as the indication, which the examination rather than the image should supply.

Fellowship Level

Where It Misleads

In revision practice this pattern is the explanation for the commonest referral in the whole of Section 4: a reconstructed knee with a firm Lachman and a patient who does not trust it.

That knee has rotational instability over a competent graft, and the pattern is established by the pivot shift under anaesthesia rather than in clinic. 4.14.6 covers that setting.

Adding a lateral procedure at revision is the usual answer, and establishing that the graft itself is competent before doing so is what the Lachman test contributes. 4.10.12 covers revision assessment.

A patient with the same complaint, a firm Lachman and a normal pivot shift under anaesthesia has a confidence problem rather than a mechanical one, and operating on that knee makes it worse. 4.22.6 covers the score built for the question.

In a knee with a previous tenodesis the shift can be mechanically abolished over an incompetent graft, so the pattern is unreadable and the translation carries the assessment. 3.11.7 covers the procedure.

A knee with a deficient lateral meniscus will show a large shift after a technically sound reconstruction, and that is a meniscal problem presenting as a ligament one. 4.9.10 covers meniscal deficiency.

In medicolegal work the distinction between a graded shift under anaesthesia and an awake impression is the distinction that carries the opinion. 4.23.7 covers that setting.