The Lachman Test is performed by the clinician to assess laxity of the anterior cruciate ligament when there is a suspected tear.

Page updated February 2024 by Dr Sheila Strover (Clinical Editor)

Lachman Test
Showing the position of the examiner's hands for performing the Lachman test.

 

What does the Lachman test measure?

The Lachman test assesses three things:

  • how far in millimetres the tibia moves forward in relation to the femur

  • how this compares with the same test in the unaffected knee. Five mm or more is highly suggestive of a complete ACL tear.

  • how abrupt the endpoint feels, ie a hard endpoint ('A') or a soft endpoint ('B')

 

 

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How is the Lachman test performed?

With the patient lying on their back and the head supported, the knee is flexed to 20-30 degrees, and the patient encouraged to totally relax. One hand grasps the femur, while the other grasps the upper tibia with the fingers at the back of the tibia and the thumb in front. Attempt is made to displace the tibia in relation to the femur, feeling both for the degree of displacement and the firmness of the end point.

  • Quote from peer-reviewed paper:

    "Grading of ACL laxity is described as 1 through 3, which correlates to mild, moderate, and severe ACL injuries. Mild (grade I) is 0 to 5 mm, moderate is 6 to 10 mm (grade II), and severe is 11 to 15 mm (grade III) of anterior tibial translation compared to the uninjured side."

    Citation: Coffey R, Bordoni B. Lachman Test. [Updated 2023 Jul 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK554415/

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How accurate is the Lachman test?

The Lachman test is not the most accurate of the manual tests for an anterior cruciate ligament tear. If there is blood in the knee, the test may be painful and trigger hamstrings spasm.

Other tests include -

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Forum discussions

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Dr Sheila Strover (Editor)
BSc (Hons), MB BCh, MBA

See biography...

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