From the Guidelines
The Lachman test is a crucial physical examination technique used to assess the integrity of the anterior cruciate ligament (ACL) in the knee, and it is considered a key criterion for evaluating knee stability, as highlighted in the recent 2023 clinical practice guideline on rehabilitation after anterior cruciate ligament reconstruction 1. To perform the test, the patient lies supine with the knee flexed at approximately 20-30 degrees. The examiner places one hand behind the proximal tibia and the other on the distal femur, then pulls the tibia forward while stabilizing the femur.
- A positive test is indicated by excessive anterior translation of the tibia relative to the femur and/or a soft or absent endpoint, suggesting ACL damage.
- The test is considered more accurate than the anterior drawer test because the knee position during Lachman's test reduces hamstring tension, which can otherwise mask ACL instability.
- Sensitivity for detecting ACL tears is approximately 85-95%, as supported by the latest research 1. When performing this test, it's essential to compare findings with the uninjured knee to establish a baseline for normal laxity, as some individuals naturally have greater joint laxity than others.
- If a positive Lachman's test is found, further imaging such as MRI is typically recommended to confirm the diagnosis and assess for associated injuries. The Lachman test is a vital component of the evaluation process, as emphasized in the 2023 guideline, which proposes minimum criteria for clearing professional athletes to return to sport, including a stable knee as assessed by the Lachman test, among other factors 1.
From the Research
Definition and Purpose of the Lachman Test
- The Lachman test is a clinical test used to assess the integrity of the anterior cruciate ligament (ACL) in the knee 2, 3, 4, 5, 6.
- It is used to evaluate the stability of the knee joint and to diagnose ACL injuries or ruptures.
Procedure and Interpretation
- The Lachman test involves the examiner applying an anterior force to the tibia while the knee is in a slightly flexed position 2, 6.
- The test is considered positive if there is excessive anterior translation of the tibia relative to the femur, indicating a potential ACL injury 2, 4, 5.
- The Lachman test can be used in conjunction with other clinical tests, such as the pivot shift test, to assess ACL function and diagnose ACL injuries 3, 4, 5, 6.
Reliability and Validity
- Studies have shown that the Lachman test has limited reliability, with variable results depending on the examiner and the patient's condition 2.
- However, the Lachman test has been found to be a valid test for assessing ACL integrity, with high sensitivity and specificity values reported in several studies 4, 5.
- The Lachman test is considered a useful tool for ruling out ACL injuries, with a negative test result having a high predictive value for the absence of an ACL rupture 4, 5.
Comparison with Other Tests
- The Lachman test has been compared to other clinical tests, such as the pivot shift test and the anterior drawer test, in terms of its accuracy and reliability 3, 4, 5.
- The pivot shift test is considered a more specific test for assessing ACL function, but it has a lower sensitivity than the Lachman test 3, 4, 5.
- The anterior drawer test has been found to have variable results and is not considered as reliable as the Lachman test for assessing ACL integrity 4, 5.