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Lachman test

Bodyexamination

Written by manual therapists Thomas T. Ødegaard and Roar Syltebø

Dr John W. Lachman introduced his own test for the anterior cruciate ligament (ACL) of the knee in the late 1950s and early 1960s. Lachman was both an orthopaedic surgeon and a teacher of medical students, and he had examined countless knees. Early in his career he had noticed that some patients with an ACL injury had an anterior subluxation of the proximal tibia relative to the femur when lying supine. On the basis of this observation, he demonstrated how easily this knee instability could be detected by stressing the knee close to extension, instead of using the classic drawer test. One of his former students, the orthopaedic surgeon Joseph Torg, was the first to describe the Lachman test in the literature, in 1976 (Torg et al., 1976).

Indication

The Lachman test is indicated in all knee examinations after trauma, when an ACL injury (partial or complete tear) is suspected and the main symptom is that the knee gives way. ACL injuries are usually associated with a rotational trauma that causes severe pain and rapid swelling (Bahr & Mæhlum, 2002).

Procedure

Torg, who was the first to describe the Lachman test, described the procedure as follows in his original article (Torg et al., 1976). The patient lies supine. The clinician stands on the same side of the examination table as the knee being examined. The patient’s knee is flexed to approximately 0–15°, and the clinician stabilises the patient’s distal femur with one hand while the other hand grasps the proximal tibia. The clinician pulls the tibia anteriorly, producing an anterior translation of the tibia.

Solberg and Kirkesola describe a modified version of the Lachman test in which the clinician supports the patient’s femur on their own knee (Solberg & Kirkesola, 2007). Body Examination has good experience with this modification when the clinician has small hands relative to the size of the patient’s leg.

Interpretation

The grading of a Lachman test depends on the amount of anterior translation of the tibia relative to the femur. The test is considered positive when the translation can be seen and/or felt. The end-feel is also a very important indicator of a positive test. A “mushy” and/or soft end-feel is regarded as a positive test, in contrast to a firm, hard end-feel, which according to Torg and colleagues indicates an intact ACL (Torg et al., 1976).

The Lachman test was developed because the widely used drawer test was not considered good enough. Three main differences make the Lachman test more accurate. First, the starting position, with slight flexion, is more comfortable and natural for an acutely injured knee. Second, acutely injured knees develop reflex tension or spasm in the hamstrings, and this force is more easily overcome with the knee close to full extension, which makes it possible to achieve an anterior translation of the tibia. Third, with the knee extended, the contact surface of the tibial plateau and menisci is slightly convex towards the femur. This minimises the risk of obstruction in the joint during anterior movement of the tibia, which may occur at 90° of flexion.

In his original material, Torg (1976) reported a sensitivity of 95% and a specificity of 100% for chronic ACL tears, many of which were combined meniscal and ACL injuries. Cook and Hegedus (2012) give this study a QUADAS score of 7. Five false-negative tests were reported, caused by a bucket-handle meniscal tear blocking the translation of the tibia (Torg et al., 1976).

In 1988, Lee and colleagues published a study comparing MRI findings with arthroscopy and clinical tests in patients with ACL injuries. In this study, the Lachman test had a sensitivity of 89% and a specificity of 100%. The Lachman test was better than the drawer test, but not as good as MRI, which had a sensitivity of 94% and a specificity of 100% (Lee et al., 1988).

In 1990, Cooperman and colleagues studied the reliability and validity of the Lachman test. They refer to earlier studies, mostly carried out by experienced clinicians, mainly orthopaedic surgeons (DeHaven, 1980). Earlier studies had also shown that it can be difficult to test and retest the knee at the same angle of flexion, and that this may affect the results (Donaldson et al., 1985). The aim of the study was therefore to examine the inter- and intra-examiner reliability and the validity of the test among physiotherapists and orthopaedic surgeons. Two orthopaedic surgeons, two physiotherapists and 32 patients took part. The orthopaedic surgeons had at least 15 years of clinical experience, and the physiotherapists at least five years. For the judgement of whether the Lachman test was positive or negative, intra-examiner kappa was 0.44 for the physiotherapists and 0.60 for the orthopaedic surgeons, with an overall kappa of 0.51 and an overall agreement of 76%. Inter-examiner kappa was 0.69 for the physiotherapists, 0.61 for the orthopaedic surgeons and 0.42 for all examiners, with an overall agreement of 60–71%. The positive predictive value was 47% for all examiners, and the negative predictive value 70%. Cooperman and colleagues conclude that the Lachman test has limitations with regard to reliability, and that it may be more useful for predicting that the patient does not have an ACL injury than that they do (Cooperman et al., 1990).

In a review from 2001, Solomon and colleagues analysed the accuracy of clinical tests compared with arthroscopy, MRI and arthrotomy. They reviewed the English-language literature in Medline and HealthSTAR from 1966 to 2000. Of 88 articles identified, 23 (26%) were included. A rheumatologist and an orthopaedic surgeon independently rated the studies using a standardised rating scale. The sensitivity of the Lachman test varied from 60% to 100%, with a mean of 84%. The summary likelihood ratio was 25.0 (95% CI 2.7–651.0) for a positive test and 0.1 (95% CI 0.0–0.4) for a negative test (Solomon et al., 2001).

In a large review from 2003, Malanga and colleagues systematically searched the Medline database from 1970 to 2000. Their aim was to trace the original descriptions of clinical tests and then assess their scientific validity and accuracy. They concluded that the Lachman test appears to be a very sensitive and specific test for detecting ACL injuries. At the same time, modified versions of the Lachman test have been introduced that have not been studied to the same extent. Clinicians must therefore be aware of their responsibility, and there is a need for better standardisation of how tests are performed and how test results are compared (Malanga et al., 2003).

In a meta-analysis from 2006, Benjaminse and colleagues assessed the accuracy of clinical tests for detecting an ACL injury. They searched three large databases (Medline, Embase and CINAHL) from 1966 to 2005, limited to articles in English, German and Dutch. After screening, 28 heterogeneous studies were included. They concluded that the Lachman test was the most valid clinical test for detecting ACL tears. The results were:

Sensitivity 85%
Specificity 94%
Negative likelihood ratio 0.2
Positive likelihood ratio 10.2
Diagnostic odds ratio 70

The meta-analysis therefore concluded that the Lachman test is the best clinical test to recommend when an ACL injury is suspected (Benjaminse et al., 2006).

In a meta-analysis of acute, complete ACL tears, van Eck et al. (2013) found that, in the clinic without anaesthesia, the Lachman test had a sensitivity of 81% and a specificity of 81%. Under anaesthesia, the sensitivity increased to 91% and the specificity was 78%. Without anaesthesia, the Lachman test had the highest sensitivity of the three tests studied, while the Lachman test, the anterior drawer test and the pivot shift test had comparable specificity (van Eck et al., 2013).

A more recent systematic review with meta-analysis by Sokal et al. (2022) included 24 studies. Using a statistical method that takes account of the relationship between sensitivity and specificity (bivariate analysis), they found a sensitivity of 81% (95% CI 73–87%) and a specificity of 85% (95% CI 73–92%) for the Lachman test, corresponding to a positive likelihood ratio of 5.7 and a negative likelihood ratio of 0.24. More than three weeks after injury, the sensitivity was 70% and the specificity 77%. The authors conclude that the accuracy of the Lachman test has previously been overestimated, partly because earlier reviews included patients with additional ligament injuries. The Lachman test, the anterior drawer test and the lever sign had comparable overall accuracy, while the pivot shift test was best for confirming an ACL tear (Sokal et al., 2022).

In a meta-analysis of patients with a suspected acute ACL injury, Tanaka et al. (2022) found a sensitivity of 79% and a specificity of 91% for the Lachman test (Tanaka et al., 2022).

Décary et al. (2018) studied 279 patients with knee complaints from orthopaedic and family medicine clinics. The Lachman test had a positive likelihood ratio of 38.4 and a negative likelihood ratio of 0.19. A combination of a pivoting injury mechanism, immediate swelling and a positive Lachman test gave a positive likelihood ratio of 17.5. If the patient reported neither a pivoting injury nor a “popping” sensation, and both the Lachman test and the pivot shift test were negative, the negative likelihood ratio was 0.08. The authors conclude that combinations of history and physical examination findings can support the diagnosis of an ACL tear (Décary et al., 2018).

As already mentioned, the Lachman test has been modified over time. In their book from 2007, Solberg and Kirkesola describe the Lachman test performed at 20–30° of flexion, with the clinician’s knee placed under the patient’s femur. They also describe how a quick jerk of the tibia can be used to test the ACL (Solberg & Kirkesola, 2007).

In their book, Cook and Hegedus (2012) give the Lachman test a utility score of 1, meaning that the evidence strongly supports its use in the diagnosis of ACL injuries (on a scale from 1, strong support, to 3, minimal or no support). This assessment reflects the literature up to 2012, when the Lachman test was regarded as the most accurate clinical ACL test. The more recent reviews described above call this score into question. They found that the accuracy of the Lachman test has previously been overestimated, and that it is comparable to that of the anterior drawer test and the lever sign (Sokal et al., 2022; Tanaka et al., 2022).

Body Examination suggests the following interpretation of the Lachman test:

Literature search, updating and translation were carried out with the assistance of AI (Claude, Anthropic). The professional content has been reviewed and quality-assured by the editor-in-chief, Roar Syltebø.

References

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