Anterior Drawer Test

For Medical Students

What It Tests

The anterior drawer measures anterior translation of the tibia on the femur with the knee flexed to about ninety degrees.

It is testing the same thing as the Lachman test, in a worse position, and the comparison between them is the most instructive thing in this chapter. 4.10.4 covers the Lachman.

At ninety degrees the hamstrings are lengthened and well placed to resist the translation the test is trying to produce, so a tense patient resists easily and the test under-reports.

How It Is Performed

With the patient supine, flex the knee to about ninety degrees with the foot flat on the couch.

Sit lightly on the foot to stabilise it, or ask an assistant to hold it.

Check that the hamstrings are relaxed by palpating them with your fingers behind the proximal tibia, which is part of the technique rather than an optional refinement.

Grasp the proximal tibia with both hands and apply a firm anterior force, feeling the translation and the endpoint.

Compare with the other knee, and note the starting position, because a posteriorly sagged tibia gives a falsely large anterior excursion. 4.11.1 covers the posterior sag sign.

What a Positive Means

Increased anterior translation with a soft endpoint, compared with the other side, is a positive and indicates a ruptured anterior cruciate.

A negative test is weak, much weaker than a negative Lachman, and should not be recorded as excluding the injury.

A falsely positive result occurs when the tibia starts posteriorly because the posterior cruciate is torn, and the tibia is being reduced rather than translated forwards. 4.11.2 covers the posterior drawer.

A positive test with the hamstrings tense is uninterpretable, which is why palpating them is part of the method.

The test also assesses the secondary restraints, which contribute more at ninety degrees than at thirty. 3.7.3 covers secondary restraints.

MRCS Level

How It Is Performed

In a viva the expected points are the flexion angle, the stabilised foot, the hamstring check, the starting position, and the comparison.

The candidate is likely to be asked why the Lachman is better, and the answer is the hamstring length at the test position, not examiner skill.

Say that you would check for a posterior sag before interpreting an anterior drawer, because a torn posterior cruciate makes this test misleading. 4.11.1 covers the sag.

Say that the test adds information about the secondary restraints and about rotation if performed with the tibia internally and externally rotated, which is the Slocum modification. 4.14.2 covers it.

What a Positive Means

The reasoning expected is flexion-dependent restraint. The anterior cruciate restrains anterior translation throughout the range and the secondary restraints contribute more in flexion. 3.7.2 covers primary restraints.

So the anterior drawer tests a composite rather than the ligament alone, which is a second reason it is less specific than the Lachman.

Adding rotation makes the test assess the anteromedial and anterolateral structures, which is the useful extension of it and is why it survives in practice. 4.12.6 covers anteromedial rotatory assessment.

A gross anterior drawer with the tibia in external rotation raises a medial side injury alongside the cruciate. 4.12.7 covers the separation.

How Good It Is

The anterior drawer is substantially less sensitive than the Lachman test and that comparison is the best established in the knee examination literature. 3.17.1 covers the studies.

It is particularly poor acutely, where guarding and hamstring tension are at their worst. 4.10.2 covers the acute knee.

It performs better in a chronic knee and still does not reach the Lachman.

Its enduring value is in the rotational modifications and in assessing the posterior cruciate in the same position, rather than as a primary anterior cruciate test.

No figures appear, under decision 023, and the ranking is the claim.

FRCS Level

How Good It Is

At decision level the anterior drawer earns its place as part of a sequence rather than as a test of the anterior cruciate.

The ninety degree position is where the posterior drawer, the posterior sag and the rotational modifications are all performed, so the position is efficient even if the anterior test within it is weak. 4.11.2 covers the posterior drawer.

Where it adds unique information is in a knee with a suspected combined injury, because rotation at this angle separates medial and lateral rotatory instability. 4.14.4 covers anteromedial rotatory instability.

It should not be used as the basis for a reconstruction decision, and a letter reporting only an anterior drawer has not assessed the ligament adequately.

Where It Misleads

The commonest error is using it as the primary anterior cruciate test, which the evidence does not support.

The second is not excluding a posterior sag, which produces a false positive and is a recognised trap.

The third is performing it on a tense patient and recording the result, when the finding is about the hamstrings.

And interpreting a negative drawer in an acute knee as reassuring, which is the error this chapter names most often.

Fellowship Level

Where It Misleads

At this level the anterior drawer is mainly a vehicle for the rotational modifications, and that is how it should be taught.

In a multiligament knee the ninety degree position allows anterior and posterior translation and rotation in both directions to be assessed in one setup, which is efficient in a knee that will not tolerate much. 4.23.6 covers the assessment.

In a revision assessment a gross anterior drawer with rotation suggests a medial or lateral component that was not addressed, which is the recurring finding of this chapter. 4.10.12 covers it.

The honest teaching point is that a test can survive in practice for reasons unrelated to its accuracy, in this case because its position is useful, and recognising that is better than either defending or discarding it.

No figure here supports these claims, under decision 023.