Lachman test

The Lachman Test is a passive clinical test for the knee designed to evaluate the integrity of the anterior cruciate ligament (ACL). It is considered one of the most sensitive and specific physical examination tools for detecting ACL ruptures and is especially valuable for assessing sagittal plane instability.

Anatomical background

The ACL is a central stabilizing ligament of the knee that prevents anterior translation of the tibia relative to the femur. Damage or rupture of the ACL leads to loss of knee stability, functional instability, and an increased risk of secondary meniscal injuries and degenerative changes over time.

Before performing the Lachman Test, the integrity of the posterior cruciate ligament (PCL) should be assessed, since a PCL rupture may affect the accuracy of the test.

Test procedure

Patient position

• The patient lies supine on the examination table.

• The knee is flexed 20–30°, supported either by the examiner’s knee or a small bolster.

• The leg is slightly externally rotated for optimal positioning.

Examiner grip

• One hand stabilizes the femur.

• The other hand grasps the tibia just below the tibial tuberosity, with the thumb placed on the anterior aspect of the knee.

Execution

• A quick, controlled anterior translation of the tibia relative to the femur is applied.

• The examiner observes the amount of anterior movement and evaluates the end-feel.

Interpretation of results

• Negative test:

  • Minimal anterior translation.

  • Firm, distinct end-feel → Indicates intact ACL.

• Positive test:

  • Increased anterior translation (>2 mm compared with the contralateral side).

  • Soft or absent end-feel (“soft end-feel”).

  • Translation >10 mm strongly suggests ACL rupture.

  • Instrumented devices such as the KT-1000 arthrometer can provide objective confirmation.

Modifications of the Lachman Test

1. Stable Lachman Test

   • Used when the examiner has small hands.

   • Patient supine, knee rests on examiner’s thigh while femur is stabilized and anterior translation applied.

2. Drop Leg Lachman Test

   • Increases sensitivity.

   • Patient supine with the tested leg abducted over the edge of the table.

   • Knee flexed to 25°, femur stabilized against the table, tibia pulled anteriorly.

3. Modified rotational technique

   • As described by Frank, tibia is slightly laterally rotated and anterior translation applied from a posteromedial direction to improve sensitivity.

Scientific evidence

• Systematic reviews confirm that the Lachman Test is the most sensitive ACL test, with excellent intra- and inter-rater reliability [5][6].

• A comprehensive review found the Lachman Test to be the only clinical test that can confirm or exclude ACL rupture on its own [7].

Reported diagnostic values:

• Acute ACL ruptures (<2 weeks): Sensitivity ≈ 77.7%.

• Chronic ACL ruptures (>2 weeks): Sensitivity ≈ 84.6%.

• Specificity: >95% in both cases [8].

• Studies under anesthesia show even higher accuracy, but results may be slightly lower in routine clinical practice.

Clinical considerations

• Acute injuries:

  • Swelling can limit accuracy.

  • Best performed immediately post-injury before swelling develops, or in the chronic phase once swelling subsides.

• False results:

  • False positive: PCL rupture causing posterior sag.

  • False negative: Strong hamstring contraction or high muscle tone masking anterior laxity.

• Comparison with other ACL tests:

  • Pivot Shift Test: More specific for functional instability.

  • Anterior Drawer Test: Less sensitive, but more reliable in chronic ACL ruptures.

Conclusion

The Lachman Test is the most reliable and sensitive clinical examination for detecting ACL rupture, especially in acute injuries. It provides more accurate assessment than the anterior drawer test and should be the primary manual test used when ACL injury is suspected. A positive result should always be confirmed with imaging (MRI) and functional assessment to guide treatment and rehabilitation planning.

References

1. Mulligan EP, Anderson A, Watson S, Dimeff RJ. THE DIAGNOSTIC ACCURACY OF THE LEVER SIGN FOR DETECTING ANTERIOR CRUCIATE LIGAMENT INJURY. Int J Sports Phys Ther. 2017 Dec;12(7):1057-1067.

2. Scott Holmes and Eric Sorenson, Lachmans Test, http://www.youtube.com/watch?v=bHytLhg-1vM, online video, last accessed 30 November 2009

3. Adler GG, Hoekman RA, Beach DM. Drop leg Lachman test: a new test of anterior knee laxity. The American journal of sports medicine. 1995 May;23(3):320-3.

4. CRTechnologies.Drop Leg Lachman Test (CR) . Available from:https://www.youtube.com/watch?v=cHgtxuoKNrE

5. Prins M. The Lachman test is the most sensitive and the pivot shift the most specific test for the diagnosis of ACL rupture. Australian journal of physiotherapy. 2006;52(1):66–66.

6. Lange T, Freiberg A, Dröge P, Lützner J, Schmitt J, Kopkow C. The reliability of physical examination tests for the diagnosis of anterior cruciate ligament rupture – A systematic review. Manual therapy. 2015;20(3):402–11.

7. Décary S, Ouellet P, Vendittoli PA, Roy JS, Desmeules F. Diagnostic validity of physical examination tests for common knee disorders: An overview of systematic reviews and meta-analysis. Physical therapy in sport. 2017;23:143–55.

8. Katz JW, Fingeroth RJ. The diagnostic accuracy of ruptures of the anterior cruciate ligament comparing the Lachman test, the anterior drawer sign, and the pivot shift test in acute and chronic knee injuries. The American Journal of Sports Medicine 1986;14:88-91. http://ajs.sagepub.com/content/14/1/88.short (accessed 18 July 2013)

9. Frank C. Accurate interpretation of the Lachman test. Clinical orthopaedics and related research. 1986 Dec(213):163-6.