Reverse Pivot Shift

For Medical Students

What It Tests

The reverse pivot shift looks for the lateral side of the tibia sliding forward from a posteriorly subluxed position as the knee is brought out of flexion.

It is the mirror image of the pivot shift. There, the tibia subluxes forward in extension and reduces in flexion. Here, it subluxes backwards in flexion and reduces as the knee extends. 4.10.6 covers the forward version.

The combination it detects is a deficient posterior cruciate with a deficient posterolateral corner, because the corner is what resists the external rotation the test applies. 3.8.2 covers posterior stability.

How It Is Performed

Position the patient supine and relaxed, with the knee flexed to about seventy degrees or more and the foot held in your hand.

Apply a valgus force at the knee and hold the tibia in external rotation.

Extend the knee slowly while keeping both forces applied, and feel for a shift rather than looking for one.

The shift occurs as the knee passes about twenty to thirty degrees of flexion, where the iliotibial band changes from a flexor to an extensor of the knee and pulls the lateral plateau forward.

Compare with the other knee in exactly the same hands and the same forces, which matters more on this test than on any other in the chapter.

What a Positive Means

A palpable shift or clunk as the lateral plateau reduces during extension is a positive test.

It indicates that the lateral side of the tibia was subluxed posteriorly in flexion, which requires both the posterior cruciate and the posterolateral structures to be deficient. 4.11.7 covers the combined injury.

A positive test is therefore a statement about two structures rather than one, and it is one of the few examination findings that cannot be produced by an isolated cruciate tear.

A positive result occurs in a proportion of normal knees, particularly relaxed or hypermobile ones, so an uncompared positive is close to meaningless. 4.23.3 covers hypermobile patients.

MRCS Level

How It Is Performed

In a viva the expected points are the starting flexion, the valgus force, the external rotation, the slow extension, and the comparison.

Say that the test needs the patient relaxed, because a tense hamstring prevents the subluxation the test is trying to reduce.

Say which way round the shift goes, because the commonest error in a viva is describing the pivot shift and calling it the reverse. 4.10.6 covers the forward version.

Say that you would perform it after the sag sign and the posterior drawer rather than before, because a rotational test on an unreduced knee is hard to interpret. 4.11.2 covers the drawer.

Say that you would compare sides and record both, since a positive on one side alone is the finding.

What a Positive Means

The reasoning expected is that the iliotibial band lies behind the axis of rotation in flexion and in front of it near extension, so its line of pull reverses as the knee extends and supplies the reducing force.

The posterolateral structures resist external rotation of the tibia, so when they are deficient the plateau can rotate and translate backwards under a valgus load. 3.8.2 covers that restraint.

The posterior cruciate is required as well, because it resists the posterior component of the same movement, which is why this test is a two structure finding rather than a corner test alone. 4.13.4 covers the corner.

An increase in external rotation at thirty degrees of flexion and at ninety degrees in the same knee points the same way and is easier to grade, which is why the dial test is usually the test that settles it. 4.13.5 covers the dial test.

How Good It Is

The reverse pivot shift is specific for a combined posterior and posterolateral injury when it is clearly positive on one side only, and it is unreliable in every other circumstance.

Its central problem is a positive result in relaxed normal knees, which is well described and is the reason the test is never read in isolation.

Under anaesthesia the rate of positive results in uninjured knees rises further, because the relaxation the test needs is the same relaxation that produces a false positive. 4.23.1 covers examination under anaesthesia.

It is less reproducible between examiners than the dial test and less reproducible than either the sag sign or the drawer, because it depends on the examiner applying two forces at once while moving the joint.

No figures appear for any of these comparisons, under decision 023, and the comparison is the claim being made.

FRCS Level

How Good It Is

At decision level this test is not a diagnostic test so much as a warning that the plan under consideration is the wrong one.

A clearly positive reverse pivot shift in a knee listed for an isolated posterior cruciate reconstruction means the corner has not been assessed properly, and that is the one decision this finding genuinely changes.

It contributes nothing to grading and nothing to timing. The dial test, the varus stress test and the stress radiographs carry those. 4.13.1 covers varus stress testing.

Where it earns its place is in the examination under anaesthesia of a multiligament knee, performed on both sides, where an asymmetric shift is worth more than a positive one. 4.23.6 covers those injuries.

Where It Misleads

The commonest error is reading an isolated positive result as pathology without examining the other knee.

The second is performing it on a guarding patient, where a negative result means the hamstrings worked rather than that the ligaments are intact.

The third is describing it in the direction of the pivot shift, which turns up in operation notes and correspondence often enough to be worth distrusting.

The fourth is treating a positive result as a corner test. It needs both structures, so a positive result does not localise the injury on its own.

Fellowship Level

Where It Misleads

In revision practice the reverse pivot shift is usually the test that was not done, and the consequence is sitting in front of you.

The classic case is a stretched posterior cruciate graft in a knee whose corner was never addressed, where this test and the dial test would both have been positive before the first operation. 4.13.5 covers the dial test.

A positive test after a corner reconstruction suggests the reconstruction has failed to control rotation, which is a different problem from a cruciate graft that has stretched and is distinguished by the dial test at two angles rather than by this one.

A persistent positive result in a knee that is clinically stable and symptom free is common enough that it is not on its own a reason to reoperate, and chasing it has produced more revisions than it has solved.

The test is also unhelpful in the chronically deficient knee with a fixed posterior subluxation, because a plateau that cannot reduce cannot shift, and the examination reads as negative in the worst knee in the clinic. 4.11.6 covers that knee.

In a knee with a previous lateral soft tissue procedure the iliotibial band may no longer behave as the test assumes, so the mechanism the test depends on is not present and a negative result says nothing.