Pivot Shift

For Medical Students

What It Tests

The pivot shift reproduces the movement a patient with an anterior cruciate rupture describes: the tibia rotating and subluxing forwards on the femur, then reducing.

The technique belongs to the anterior cruciate chapter, where the test is first met. 4.10.6 covers it.

What this chapter adds is the test's place among the rotational assessments. Rotation rather than translation is the complaint, and this is the test that reads rotation. 3.11.4 covers pivot shift control.

How It Is Performed

Lay the patient supine and fully relaxed, with the knee extended.

Apply a valgus force and internal rotation to the tibia, and flex the knee from extension.

Feel for the lateral tibial plateau reducing from a subluxed position as the knee passes about twenty to thirty degrees of flexion.

Compare with the other knee using the same grip and the same forces, and grade the glide, the clunk and whether it is reproducible. 4.10.6 covers the grading.

Note that relaxation is the whole difficulty. A patient who guards prevents the subluxation, so the test fails in the direction of a false negative. 4.14.6 covers the setting that removes the guarding.

What a Positive Means

A reduction felt as the knee flexes indicates a deficient anterior cruciate.

The size of the shift reflects more than the cruciate. The anterolateral structures, the lateral meniscus and the posterior horn all contribute to rotational control, and their loss makes the shift larger. 3.11.3 covers the anterolateral ligament.

A large shift in a knee with an isolated cruciate rupture suggests additional rotational deficiency rather than a worse cruciate injury, and that distinction changes the operation. 4.14.3 covers the pattern.

A shift in a knee with an intact Lachman test should be distrusted, since the cruciate resists the translation the shift depends on. 4.10.4 covers the Lachman test.

MRCS Level

How It Is Performed

In a viva the pivot shift is the test to name when asked what correlates with the patient's symptoms, and knowing that is more useful than knowing the grip.

The expected points are the relaxed patient, the valgus and internal rotation, flexion from extension, the angle of reduction, the grading, and the comparison.

Say that the test is graded as a glide, a clunk and a gross shift, and that the grade is recorded rather than the word positive. 4.1.8 covers the record.

Say that you would perform the Lachman test first, because a pivot shift in a knee with no translation is not a pivot shift. 4.10.4 covers it.

Say that the test is unreliable awake and reliable under anaesthesia, and that the difference is relaxation rather than technique. 4.14.6 covers it.

What a Positive Means

The reasoning expected is that the anterior cruciate resists anterior translation and internal rotation, and that the pivot shift loads both at once. 3.11.5 covers internal rotation control.

The iliotibial band supplies the reducing force as its line of pull crosses the axis of rotation during flexion, which is why the reduction happens at a particular angle rather than gradually. 3.11.1 covers its function.

The Kaplan fibres and the anterolateral ligament contribute to the restraint, which is the anatomical basis for the larger shift in some knees and for the lateral extra-articular procedures that address it. 3.11.2 covers the Kaplan fibres.

The lateral meniscus posterior horn acts as a bony block to the subluxation, so its loss increases the shift and its repair reduces it. 4.9.9 covers meniscal root tears.

How Good It Is

The pivot shift is the examination finding that correlates best with the patient's complaint and worst with reproducibility, and both halves of that matter.

It is specific rather than sensitive awake. A positive result is close to diagnostic and a negative one excludes little, because guarding produces the negative.

It is considerably more reliable under anaesthesia, which is why it appears in operation notes more than in clinic letters. 4.14.6 covers that setting.

Instrumented measurement of the shift exists and has not displaced the manual grading in practice, which is worth knowing when a number appears in a letter from a research unit.

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 the pivot shift grade is one of the few examination findings that changes the operation rather than the diagnosis.

A large shift in a knee having an anterior cruciate reconstruction is the main clinical argument for adding a lateral extra-articular procedure, and that decision rests on this test. 3.11.7 covers the procedure.

The grade also contributes to the return to sport decision after reconstruction, where a persisting shift in an athlete is a different problem from a stable knee with a confidence complaint. 4.22.6 covers the score built for that question.

It contributes little to whether to reconstruct at all, which is a functional decision, and this chapter's argument is that the test which measures the complaint still does not make that decision. 4.10.3 covers the chronic knee.

Where the awake grade and the patient's account disagree, examination under anaesthesia settles it, and in a revision setting that is worth arranging deliberately. 4.14.6 covers it.

Where It Misleads

The commonest error is recording positive or negative rather than the grade, which discards the information the test carries.

The second is reading a negative result in a guarding patient as a normal knee.

The third is attributing a large shift to a severe cruciate tear rather than to additional rotational deficiency.

The fourth is performing it without the Lachman test, which leaves nothing to corroborate it.

The fifth is comparing with the other knee only when the result is abnormal, which removes the baseline in exactly the cases that need it.

Fellowship Level

Where It Misleads

In revision practice the pivot shift is the finding that separates a graft that has failed from a knee that was never rotationally controlled.

A patient with a reconstructed cruciate, a firm Lachman and a persisting pivot shift has rotational instability over a competent graft, and that is an anterolateral problem rather than a graft problem. 4.14.3 covers it.

That knee is the main indication for a lateral extra-articular procedure at revision, and the examination is what identifies it rather than the imaging. 3.11.8 covers the combination.

A persisting shift with a loose Lachman is a failed graft, and the two are distinguished by the translation rather than by the rotation. 4.10.4 covers the Lachman test.

In a knee with a previous tenodesis the shift may be abolished mechanically while the graft is incompetent, so a negative pivot shift no longer excludes a failed reconstruction. 3.11.7 covers the procedure.

A knee with a posterolateral corner injury gives a larger shift for the same cruciate injury, and attributing all of it to the cruciate leads to a revision that does not hold. 4.13.4 covers the corner.

In medicolegal work an awake pivot shift is weak evidence in either direction, and an operative note recording it under anaesthesia is strong. 4.23.7 covers that setting.