Pivot Shift Test

For Medical Students

What It Tests

The pivot shift reproduces the rotational subluxation and reduction that a patient with a deficient anterior cruciate feels when the knee gives way.

That makes it the test most closely related to the symptom, which is different from being the test most likely to be positive. 3.7.9 covers the mechanics.

It tests the anterior cruciate and the anterolateral structures together, because both resist the motion being provoked.

How It Is Performed

With the patient supine and as relaxed as possible, hold the foot and ankle with one hand and the lateral proximal tibia with the other.

Start with the knee extended, apply internal rotation and a valgus force, and flex the knee smoothly.

Feel for the lateral tibial plateau reducing from a subluxed position as the knee flexes, which is the shift.

Grade it by whether a glide, a clunk or a gross subluxation is felt, and compare with the other side.

Expect to fail in an awake, apprehensive or acutely injured patient, and do not force it. 4.10.2 covers the acute knee.

What a Positive Means

A felt reduction of the lateral plateau during flexion is a positive and indicates rotational instability.

A positive pivot shift corresponds more closely to the patient's complaint of giving way than any other finding in this chapter. 4.2.6 covers giving way.

A negative test in an awake patient excludes very little, because guarding abolishes it.

A gross pivot shift raises an anterolateral or lateral side injury alongside the cruciate. 4.13.8 covers combined lateral injuries.

A positive test in the absence of a positive Lachman is unusual and should prompt review of both.

MRCS Level

How It Is Performed

In a viva the expected points are the starting position, the internal rotation and valgus, the smooth flexion, the felt reduction, the grading and the comparison.

The candidate should say that patient relaxation is the limiting factor and that the test is frequently not obtainable awake.

Say that the grading is a glide, a clunk or gross, and that you would record the grade with the side comparison.

Say that the test is transformed by anaesthesia, which is why it is the main reason to perform an examination under anaesthetic. 4.10.10 covers it.

What a Positive Means

The reasoning expected is that the shift is a rotational subluxation, not an anterior translation, and the two are separate findings.

In extension with valgus and internal rotation the lateral plateau subluxes anteriorly because the cruciate is not resisting it. As the knee flexes the iliotibial band becomes a flexor and reduces it, which is the clunk. 3.7.9 covers the mechanics.

That dependence on the iliotibial band explains why the test varies with soft tissue tension and with the anterolateral structures' integrity.

It also explains why a gross shift suggests an additional lateral injury rather than a worse cruciate injury. 4.14.3 covers anterolateral rotatory instability.

How Good It Is

The pivot shift is specific and insensitive awake, which is the opposite of the Lachman test, and the two therefore complement each other.

Its specificity is high enough that a positive result awake is strong evidence.

Its sensitivity awake is low, because guarding abolishes it, and a negative result therefore means little.

Under anaesthesia its sensitivity rises substantially, which is the single clearest example in this section of a test's performance depending on the conditions rather than the technique.

No figures appear, under decision 023, and the comparison with the Lachman and the anaesthetic effect are the claims being made.

FRCS Level

How Good It Is

At decision level the pivot shift is the test that most closely relates to the indication, because the indication is instability and this is the instability.

A high grade pivot shift in a patient with rotational symptoms supports both reconstruction and consideration of an additional lateral procedure, which 3.17.5 treats as the least settled balance in that chapter.

A persisting pivot shift after reconstruction is the clinical definition of a functionally failed graft even when the Lachman is satisfactory. 4.10.11 covers post-reconstruction assessment.

Its awake unavailability is the practical problem: the test that matters most is the one you are least likely to obtain in clinic, which is why an examination under anaesthetic is worth the anaesthetic in selected cases.

Where It Misleads

The commonest error is recording a negative pivot shift from an awake examination as evidence of rotational stability.

The second is forcing the test in an apprehensive patient, which produces a guarded knee, no finding and a loss of trust.

The third is grading it without a side comparison, since physiological laxity can produce a glide bilaterally.

And attributing a high grade shift to a worse cruciate injury rather than to an additional lateral injury, which changes the operation. 4.13.4 covers posterolateral assessment.

Fellowship Level

Where It Misleads

At this level the pivot shift is the chapter's central problem in a single test: it measures what the patient complains about and it is the least obtainable finding in the chapter.

That gap is why rotational instability is the commonest thing missed before a reconstruction and the commonest residual complaint after one. 4.10.9 covers it.

In a revision assessment the pre-operative pivot shift grade is frequently absent from the record, which makes it impossible to say whether the current rotational complaint is new. 4.1.8 covers the record.

Quantified pivot shift measurement exists, using accelerometers or image analysis, and has not entered routine practice, so the clinical grading remains the available instrument.

The practical conclusion is that an examination under anaesthetic should be performed and recorded whenever a knee is being operated on and the rotational state is relevant, which is most of them. 4.10.10 covers it.

No figure here supports these claims, under decision 023.