Lachman test and anterior drawer !

Maneuver

Pulling the shin forward with the knee bent shows whether the anterior cruciate ligament is torn: the tibia slides too far and without a firm stop.

Updated 2026-11-01

See it in 3D: ACL · Tibia · Femur · PCL

What it is

The Lachman test and the anterior drawer measure how far the tibia slides forward on the femur. The anterior cruciate ligament (ACL) is the main restraint; when it tears, the tibia moves further and without a firm end point. The Lachman, done with the knee almost straight, is the most useful bedside test for ACL tear, a common injury in pivoting sports.

The anatomy it tests

The ACL runs from the inner side of the lateral femoral condyle to the front of the tibial plateau and stops the tibia sliding forward on the femur.
At 20-30 degrees of flexion the ACL is almost the only restraint to forward translation, which is why the Lachman is more reliable.
At 90 degrees the menisci and tense hamstrings also hold the tibia and can hide a tear on the drawer test.
The posterior cruciate ligament stops the tibia moving backward.

How to do it

Patient supine and relaxed; examine the healthy knee first to learn its normal laxity.
Lachman: knee at 20 to 30 degrees of flexion; one hand holds the thigh just above the knee and the other grips the proximal tibia from behind.
Pull the tibia forward with a firm, brief movement, without rotating it, and feel the translation and the end point.
Positive Lachman: the tibia moves further forward than on the healthy side and the end point is soft or absent.
Anterior drawer: hip at 45 degrees and knee at 90 degrees with the foot flat; the examiner sits on the foot to fix it.
Before pulling, look at the knee from the side: if the tibia sags backward, the posterior cruciate ligament is injured.
Wrap both hands around the proximal tibia, thumbs on the joint line, check that the hamstrings are relaxed and pull forward.
Positive anterior drawer: increased forward translation without a firm stop; pushing backward in the same position tests the posterior cruciate.

What a positive result means

Positive Lachman: ACL tear very likely.
Typical mechanism: a twist or sudden stop on a planted foot, an audible pop, swelling within hours (hemarthrosis) and a knee that gives way.
Posterior drawer or posterior sag of the tibia: posterior cruciate ligament injury.
A negative Lachman makes ACL tear unlikely; a negative anterior drawer does not rule it out.
In the acute knee, pain, effusion and hamstring guarding can cause false negatives.

Usefulness and limits

The Lachman is the most useful bedside test for ACL tear; the anterior drawer is the least useful.
The pivot shift test is very specific but hard to do in an awake patient in pain.
MRI confirms the tear and shows associated meniscal and ligament injuries.

Test yourself

Think of the answer, then tap the question to see it.

At what knee flexion angle is the Lachman test done?

Between 20 and 30 degrees of flexion.

Why is the Lachman more reliable than the anterior drawer?

Because at 20-30 degrees the ACL is the main restraint and the menisci and hamstrings interfere less than at 90 degrees.

What should be checked before reading an anterior drawer?

Whether the tibia sags backward: it means a posterior cruciate injury and can mimic a positive anterior drawer.

What does a knee effusion that appears within a few hours of a twist suggest?

Hemarthrosis, whose most common cause is an anterior cruciate ligament tear.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

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Educational content on the clinical exam; it is learned and practised under supervision. It does not replace assessment by a health professional and is not for self-diagnosis.

Sources: Evaluating the Patient with a Knee Injury (American Family Physician (American Academy of Family Physicians), 2005); Musculo-Skeletal Examination – Knee Exam (UC San Diego School of Medicine, Practical Guide to Clinical Medicine, 2026).

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