Lachman Literature

For Medical Students

What the Question Was

The question was how to detect a torn anterior cruciate by hand, and the first answer was the anterior drawer, performed with the knee at a right angle.

The drawer turned out to be unreliable in the injured knee, because the hamstrings resist it and a torn meniscus can block the translation it is trying to produce. 4.10.5 covers the drawer.

The question became how to test the same restraint in a position where the muscles cannot defeat it, which is the question the Lachman answers. 4.10.4 covers the test.

What It Showed

The work established that a near extended knee gives a more reliable anterior test than a flexed one, and that is the finding behind current practice.

It also established that the quality of the end point matters as much as the distance, which is why the test is described in those terms. 4.7.5 covers the end feel.

It did not produce a single agreed way of grading the result, which is why grading remains a judgement by hand. 4.23.7 covers what that costs in a report.

MRCS Level

What Was Done

Torg described the test now in use, in a near extended knee, and the name attached to it is Lachman's after the surgeon who taught it. 4.10.4 covers the technique.

Comparative studies of the physical tests followed, setting the anterior drawer, the Lachman and the pivot shift against arthroscopic or operative findings.

Instrumented arthrometry was developed to replace the examiner's hand with a measured displacement, which allowed the tests themselves to be assessed against a number.

Examination under anaesthesia was used to separate the restraint from the patient's guarding, which is also how the awake tests' limits were quantified. 4.23.1 covers that examination.

What It Showed

The comparative work established a stable ranking. The Lachman outperforms the anterior drawer for detecting a torn cruciate, and the pivot shift is the more specific and the less sensitive of the rotational tests. 4.10.6 covers the pivot shift test.

It established that examiner experience changes the result, which is why the test is taught by hand rather than from a description.

It established that guarding is the dominant cause of a false negative, which is the argument for the near extended position and for examination under anaesthesia. 4.23.1 covers that examination.

No sensitivity, specificity or likelihood ratio appears on this page, under decision 023 and decision 022 together. The ranking is what is recalled reliably; a specific percentage written from memory would look exactly like a correct one.

FRCS Level

What It Showed

At decision level the literature's useful product is the ranking plus the reasons for it, because the reasons tell you when the ranking does not hold.

The Lachman's advantage comes from the position, so it shrinks in a knee that cannot be held near extension. 4.5.4 covers the flexion deformity.

The end point's value comes from the restraint being intact or not, so it is preserved in a hypermobile patient where the excursion is not. 4.23.3 covers that patient.

Instrumented measurement reduced examiner variability and did not replace the examination, because the number it produces is a displacement and the clinical question is a restraint. 4.2.2 covers instability.

A negative Lachman in a knee with a convincing history is the case the literature explains rather than resolves, and guarding, a partial tear and a secondary restraint each account for some of them. 3.7.3 covers the secondary restraints.

What It Changed

It changed the first test performed on a knee suspected of a cruciate injury, which is the clearest example in the section of evidence changing an examination.

It changed the description of a positive result from a distance to a distance and an end point. 4.7.5 covers the end feel.

It made examination under anaesthesia a defensible step rather than an indulgence, by quantifying what guarding costs. 4.23.1 covers that examination.

It left grading unstandardised, so a grade in one clinic is not a grade in another. 4.1.8 covers examination documentation.

Fellowship Level

What It Changed

At fellowship level the literature's effect is visible in what is no longer argued about and in what still is.

The position of the anterior test is settled, and the grading of its result is not, which is why operative notes record a description rather than a grade. 4.1.8 covers examination documentation.

The relationship between measured anterior laxity and symptomatic instability remains loose, which is why a reconstruction is judged on function rather than on laxity alone. 4.20.1 covers the reconstruction assessment.

The partial tear remains clinically indistinguishable from a complete one with a competent secondary restraint, and nothing in this literature resolved it. 3.7.3 covers the secondary restraints.

Revision decisions rest on serial examinations of the same knee, which is a use the comparative literature did not study. 4.10.12 covers the revision assessment.

What to Read Now

Chapter 3.17 lists the biomechanical studies that explain why the position matters, which is the underlying literature for this page.

The comparative diagnostic accuracy work is where the figures this page omits belong, and a reviewer with access can add them into 4.10.4 rather than here. 4.10.4 covers the test.

The instrumented arthrometry literature is where the measurement question sits, and it is the reading for anyone considering whether a number helps.

The examination under anaesthesia literature is the reading for the guarding question. 4.23.1 covers that examination.

No reference list appears on this page. No source was retrieved, and under decision 022 a named author with a described finding is the most this process can honestly supply, with no year, journal or citation attached.