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Lachman test

The Lachman test is a clinical maneuver designed to evaluate the integrity of the (ACL) in the , assessing for excessive anterior translation of the relative to the . Performed with the patient and the flexed to 20–30 degrees, the examiner stabilizes the distal with one hand while applying an anteriorly directed force to the proximal with the other, detecting a positive result if there is more than 5 mm of translation or a soft (absent) compared to the contralateral . The test, attributed to American orthopedic surgeon John W. Lachman, was first described and popularized in the medical literature in 1976 by Joseph S. Torg and colleagues as a reliable preoperative assessment for instability in athletes. It emerged as a refinement of earlier anterior stability tests, such as the , to better isolate function by minimizing the influence of secondary restraints like the posterior horn of the , which are more taut at higher flexion angles. In performing the test, the patient lies with the slightly externally rotated for comfort, and the examiner ensures the is relaxed to avoid muscle guarding that could obscure findings; a variation, the prone Lachman test, positions the patient face down to further reduce guarding in acute injuries. Results are graded by the degree of tibial translation and the quality of the : Grade I (mild) involves 0–5 mm displacement with a firm ; Grade II (moderate) features 6–10 mm with a soft ; and Grade III (severe) shows 11–15 mm with no discernible , correlating with partial or complete rupture, respectively. These grades help clinicians differentiate injury severity and guide decisions on or surgical intervention. The Lachman test is widely regarded as the most sensitive and specific physical exam for detecting acute tears, with reported sensitivity of 87% and specificity of 93% across multiple studies, outperforming alternatives like the anterior drawer test (sensitivity 48%) and (sensitivity ~24% in acute settings). It is particularly valuable in the initial evaluation of non-contact injuries, such as those from sudden pivoting or deceleration in sports, where a "pop" sensation and immediate often accompany disruption, necessitating confirmation with MRI or . No contraindications or complications are associated with proper technique, making it a safe, non-invasive first-line diagnostic tool in orthopedic practice.

Overview

Definition and Purpose

The Lachman test is a manual clinical examination maneuver designed to evaluate the integrity of the () in the . It specifically assesses the degree of anterior translation of the proximal relative to the distal under controlled stress, which can indicate ACL deficiency if excessive laxity is present. The primary purpose of the Lachman test is to provide a non-invasive method for detecting both acute and chronic ACL injuries during physical assessments in clinical settings, such as emergency departments or orthopedic outpatient evaluations. By identifying potential ACL tears early, it supports clinical decision-making for subsequent diagnostic steps, including (MRI) confirmation or referral for surgical reconstruction, thereby aiding in the prevention of long-term instability and associated complications. The test was originally described in 1976 by Joseph S. Torg and colleagues, who named it in honor of their mentor, orthopedic surgeon John Lachman, as a refined approach to ACL assessment. It was developed to address limitations of prior maneuvers, such as the anterior drawer test, by performing the evaluation at a knee flexion angle that minimizes muscle guarding and enhances detection of partial ligament tears.

Indications and Contraindications

The Lachman test is indicated in clinical scenarios involving suspected anterior cruciate ligament (ACL) injury, particularly following traumatic events such as non-contact pivoting or twisting mechanisms common in sports like soccer, basketball, or skiing, where patients report a sudden "pop," immediate pain, effusion, or giving-way sensation. It is also appropriate for assessing chronic knee instability suggestive of ACL deficiency and for pre-operative evaluation to confirm ligament integrity prior to surgical planning. The test is suitable for both acute presentations (within 2 weeks of injury) and chronic cases, with higher sensitivity in acute settings when performed early to minimize confounding factors like muscle spasm. The Lachman test has no absolute contraindications and is generally safe when performed with proper technique. However, caution is advised in cases of acute fractures of the or tibia-fibula, as may cause discomfort or exacerbate injury. Severe swelling or hemarthrosis that restricts flexion to less than 20-30 degrees or causes significant guarding due to pain may impair accurate assessment of anterior translation and end-point stability, potentially leading to false negatives; in such cases, the test may be deferred until subsides or performed with care to account for reduced reliability. Factors like extreme apprehension or inability to relax musculature can also affect results by promoting guarding. Results are most reliable when compared to the contralateral to establish a for normal laxity, accounting for individual variations in play.

Procedure

Patient Positioning and Preparation

The patient is positioned on the examination table with the affected flexed to 20-30 degrees, achieved by placing a or the examiner's thigh under the distal if needed. The is placed in slight external rotation (and sometimes mild ) to relax the iliotibial band and facilitate the test. To establish a baseline for comparison, the contralateral uninjured is typically examined first. The examiner is positioned seated at the foot of the table, facing the patient, with one hand stabilizing the distal femur against the table to prevent rotation or posterior movement, while the other hand grasps the proximal tibia just below the joint line, with the thumb on the tibial tuberosity for leverage. In cases where additional stability is required, a modified approach places the examiner's knee beneath the patient's posterior thigh to anchor the leg. Preparation begins with ensuring patient comfort and relaxation, as muscle guarding can compromise ; this involves a clear explanation of the procedure to the patient beforehand. obstructing access to the and should be removed or adjusted, such as and no shoes or socks. The is inspected for acute swelling or , which may necessitate to reduce pain and guarding prior to testing, ideally performed soon after injury when such effects are minimal.

Examination Technique

The Lachman test is performed with the patient in a and the flexed to 20 to 30 degrees, which minimizes tension and allows optimal assessment of anterior tibial translation relative to the . The examiner stands or sits on the side of the affected , using one hand to stabilize the distal against the examination table to prevent pelvic rotation, while the other hand grasps the proximal just below the line, with the thumb on the tibial tuberosity (anteriorly) for leverage. To execute the , the examiner applies a gentle anteriorly directed force to the posterior aspect of the proximal using approximately 20 to 30 pounds (about 89 to 134 N) of pull, aiming to subluxate the forward while maintaining femoral stabilization. During this application, the examiner observes the degree of anterior tibial and palpates the quality of the feel—typically a firm, abrupt stop in intact ligaments versus a soft or absent stop in compromised cases. The test is then repeated on the contralateral for comparison, ensuring symmetry in force application and patient relaxation. A modified Lachman test enhances stability by positioning the examiner's beneath the patient's distal to anchor the leg more securely, particularly useful in patients with larger body habitus or when additional is needed. Another variation, the prone Lachman test, positions the patient face down with the flexed 30 degrees over the table edge; the examiner stabilizes the distal and applies an anterior force to the proximal , which can reduce guarding in acute injuries. In pediatric patients, the technique employs gentler force to avoid discomfort or iatrogenic injury, often performed under to achieve muscle relaxation and accurate endpoint evaluation.

Interpretation

Assessing Results

The assessment of the Lachman test focuses on two primary factors: the degree of anterior tibial translation relative to the contralateral knee and the quality of the feel during the maneuver. Translation is typically measured in millimeters by the examiner's tactile sensation, with a side-to-side difference providing a key comparative metric. A positive result is indicated by greater than 2 mm anterior translation compared to the contralateral knee, accompanied by a soft or absent , which suggests () laxity or rupture. In contrast, a negative result shows 2 mm or less of translation with a firm , implying an intact that provides normal restraint to anterior movement. The is crucial for interpretation, as it reflects the of the . A firm occurs when there is an abrupt stop to further tibial , typically due to the ACL's , whereas a soft involves gradual yielding without a clear halt, and an empty or absent signifies a complete lack of restraint, often from a full ACL tear. These distinctions help differentiate between intact, partially injured, or fully ruptured ligaments based on the mechanical feedback during the test. Equivocal findings arise when translation is approximately equal bilaterally but a soft is present, potentially indicating partial injury, or when patient factors such as pain, muscle guarding, or swelling limit a reliable . In such cases, the test is inconclusive, and adjunct diagnostic methods, including or additional clinical maneuvers, are recommended to clarify status.

Grading the Test

The Lachman test is graded according to the side-to-side difference in anterior tibial relative to the contralateral and the integrity of the encountered during the . Grade 1 laxity involves 0-5 mm of , characterized by mild with a firm or abrupt . Grade 2 indicates 5-10 mm of , reflecting moderate with a soft or absent . Grade 3 signifies greater than 10 mm of , denoting severe with no discernible . These grades carry important clinical implications for ACL injury management. A Grade 1 result often correlates with a partial tear, which may respond to conservative treatments such as bracing and without immediate . In contrast, Grades 2 and 3 typically suggest a complete rupture, prompting consideration of surgical reconstruction to restore stability and prevent long-term complications like . Grading the test relies on subjective clinical judgment, which can pose challenges to inter-rater consistency due to variations in examiner experience and technique. Studies have shown moderate inter-rater agreement for grading (65% agreement, weighted = 0.52), though reliability improves with specialized training and standardized protocols, achieving good levels ( = 0.77).

Diagnostic Accuracy

Sensitivity, Specificity, and Evidence

The Lachman test demonstrates a pooled of 85% (95% CI 81-89%) for detecting () tears when compared to as the gold standard, making it a reliable clinical tool for identifying true positives in suspected cases. This sensitivity increases in acute injuries, reaching up to 92-93.5% when performed under , due to reduced muscle guarding and pain interference. In contrast, sensitivity drops to 70-80% in chronic presentations, where secondary stabilizers may compensate for deficiency. Specificity for the Lachman test is generally high, reported as 97% in the without ; under , specificity is approximately 78%, contributing to a positive likelihood ratio of approximately 4.1. remains the definitive reference standard for validation, while (MRI) serves as a non-invasive adjunct to support clinical findings without replacing the test's role in initial assessment. A 2022 systematic review and meta-analysis in Knee Surgery, Sports Traumatology, Arthroscopy (KSSTA) highlighted that prior reports had overestimated the Lachman test's diagnostic accuracy, with pooled at 81% (95% 73-87%) and specificity at 85% (95% 73-92%) across studies, and notably lower performance ( 70%, 95% 57-80%) in post-acute cases. Complementing this, a 2024 review in affirmed the test's high accuracy against , reporting of 90% and specificity of 87.5% in a of 86 patients. Recent studies as of 2025, including one reporting 81.8% and 95.2% specificity in 150 patients, continue to support its value despite variations in timing. These findings emphasize the test's robustness for diagnosis, though integration with enhances overall diagnostic confidence.

Factors Influencing Reliability

The reliability of the Lachman test can be significantly influenced by various patient-related factors, which may lead to altered test outcomes and reduced diagnostic accuracy. In acute injuries, swelling or hemarthrosis often induces pain, muscle guarding, and spasms, thereby limiting tibial translation and increasing the likelihood of false-negative results by masking (ACL) laxity. Aspiration of prior to testing can mitigate these effects and improve . Obesity, characterized by higher (BMI >25 kg/m²), further complicates in awake patients by impeding proper hand placement and endpoint palpation, resulting in reduced (87% vs. 94% in non-obese) and lower interobserver reliability. In ACL injuries, compensatory mechanisms such as secondary stabilizer adaptations may produce a firmer feel, potentially leading to underestimation of laxity and false negatives, though overall test accuracy tends to be higher in this phase due to reduced guarding. Muscle guarding, particularly in anxious or painful patients, similarly obscures the endpoint , emphasizing the need for patient relaxation techniques during the procedure. Examiner-related variables also play a critical role in the test's reproducibility. varies with experience levels, with values typically ranging from 0.6 to 0.8 across studies, indicating moderate to substantial agreement; less experienced examiners exhibit lower (e.g., 57% vs. higher rates among experts) due to challenges in detecting subtle endpoint differences. Performing the test under substantially enhances accuracy by eliminating muscle guarding and pain inhibition, with studies showing improvements in of up to 20-30% relative to non-anesthetized conditions (e.g., from approximately 70% to 91%). Timing of the examination relative to injury onset affects reliability, with the test being less dependable in the hyperacute phase (<24 hours) owing to pronounced spasms and guarding that restrict motion. Reliability improves beyond 2 weeks post-injury, where kappa values rise to substantial levels (e.g., 0.72 vs. 0.51 in acute settings), allowing clearer endpoint evaluation as acute inflammation subsides. Concurrent injuries, such as , can mask or mimic by altering knee biomechanics; for instance, an intact may provide secondary anterior restraint, reducing detectable laxity and leading to false negatives, while combined laxity might exaggerate translation and cause false positives. Other concomitant pathologies, like , are associated with false-positive findings due to altered joint dynamics.

Comparison to Other Tests

Anterior Drawer Test

The anterior drawer test is a clinical maneuver used to evaluate anterior translational instability of the knee, primarily assessing the integrity of the anterior cruciate ligament (ACL). It is performed with the patient in a supine position, the hip flexed to 45 degrees, and the knee flexed to 90 degrees, allowing the foot to rest flat on the examination table. The examiner stabilizes the patient's foot with their own body weight if necessary, places both hands posterior to the proximal tibia just below the joint line, and applies an anteriorly directed force to the tibia while observing and palpating for excessive anterior translation relative to the femur, typically graded as normal (0-5 mm), mild (6-10 mm), moderate (11-15 mm), or severe (>15 mm). This test measures anterior tibial translation at full knee flexion, where the hamstrings are relaxed, reducing guarding effects, but secondary stabilizers such as the posterolateral and posteromedial corners are more engaged, potentially masking isolated deficiency. In contrast to tests performed at lower flexion angles, the 90-degree position places the under greater tension but may allow compensatory contributions from other structures, leading to reported sensitivities ranging from 40% to 62% and specificity of 91% for detecting tears. The anterior drawer test demonstrates poorer detection of partial ACL tears compared to complete ruptures, as residual ligament fibers and secondary restraints can limit observable translation, resulting in lower sensitivity for incomplete injuries. Additionally, it yields more false negatives in acute settings due to joint effusion and hamstring spasm, which inhibit full relaxation and obscure laxity. Due to its lower sensitivity relative to the Lachman test, the anterior drawer test is typically employed as a supplementary rather than a primary diagnostic tool for injury.

Pivot Shift Test

The is a dynamic clinical used to evaluate anterolateral rotatory of the , particularly in the context of anterior cruciate ligament () deficiency. The patient is positioned with the hip flexed to approximately 30 degrees and the in full extension. The examiner applies a valgus force to the while internally rotating the and gradually flexing the from 0 to 30-40 degrees; in a positive test, the lateral tibial plateau subluxates anteriorly relative to the lateral femoral condyle during initial flexion, then reduces with a palpable or audible "clunk" as the flexes further, reproducing the symptomatic experienced by patients during pivoting activities. This subluxation-reduction phenomenon arises from the unopposed action of the iliotibial band and secondary restraints when the is compromised. Unlike the static anterior translation assessed by the Lachman test, the pivot shift specifically detects dynamic anterolateral rotatory laxity, which involves not only the but also secondary stabilizers such as the anterolateral ligament, lateral collateral ligament, and posterolateral corner structures. It is considered the most specific clinical test for injury, with specificity ranging from 92% to 99% across studies, making a positive result highly indicative of disruption. Sensitivity varies widely, typically lower in awake patients (18-59%) due to muscle guarding but increasing to 73-95% under , where patient relaxation allows better reproduction of the instability. The test's limitations include significant patient discomfort and guarding, which reduce its reliability in awake individuals, particularly in acute settings with swelling or that hampers flexion and application. It is often less feasible immediately post-injury and may require for accurate assessment. As a complementary tool to the Lachman test, a positive pivot shift with a negative or equivocal Lachman result can suggest combined injuries, such as rupture with concomitant anterolateral ligament or posterolateral corner involvement, guiding further imaging or surgical planning.

History and Development

Origin and Evolution

The Lachman test, a maneuver attributed to orthopedic surgeon John W. Lachman, was first formally described and eponymously named in 1976, then Chairman of the Department of Orthopaedic Surgery at in , as part of clinical studies evaluating instability in athletes. Although similar anterior translation tests at low flexion angles were described earlier (e.g., by Slocum and Larson in 1950 and Fried in 1971), the Lachman test as eponymously defined gained widespread recognition in 1976 through a seminal paper by Torg et al., who highlighted its utility in preoperative assessment of () integrity, distinguishing it from earlier drawer tests by emphasizing flexion at 20-30 degrees to better isolate laxity. This development stemmed from ongoing research into anterior instability, building on prior observations of ligamentous deficiencies in sports-related injuries. The test gained prominence during the 1980s as clinical evidence demonstrated its superiority over the traditional , particularly in awake patients with acute injuries, due to reduced guarding and improved detection of subtle laxity. By the , studies further validated its application under , where it achieved near-perfect sensitivity (up to 98%) for confirming tears in cases of acute hemarthrosis, enhancing diagnostic confidence prior to . Key milestones in its evolution include precursor work in 1972 by Galway et al., who described the pivot shift phenomenon as a dynamic sign of insufficiency, laying groundwork for combined testing protocols that later incorporated the Lachman . In recent years, meta-analyses from the have refined its role in , affirming high sensitivity (pooled estimates of 81%) while emphasizing its integration with other exams for comprehensive evaluation. The American Academy of Orthopaedic Surgeons (AAOS) incorporated the Lachman test into its ACL management guidelines in 2022, recommending it as a core component of in suspected injuries to guide treatment decisions.

Etymology

The Lachman test is an eponymous clinical examination maneuver named after John W. Lachman, MD (1919–2007), an American orthopedic surgeon who was a of and served as chairman of the Department of Orthopedics at in until his retirement in 1998. The name "Lachman" derives directly from his surname, adhering to the longstanding tradition in of bestowing eponymous honors on pioneering clinicians and researchers for diagnostic techniques. The test was first formally described and eponymized in 1976 by Joseph S. Torg, MD, and colleagues in their seminal paper on instability, where they explicitly named it after Lachman, their mentor, to recognize his contributions to . In orthopedic literature, it is occasionally referred to as the "Lachman drawer test" to differentiate it from the related , emphasizing its assessment of anterior tibial translation. While no widely adopted alternative names exist, research has introduced variants such as the "active Lachman test," in which the patient actively contracts the to elicit , enhancing diagnostic utility in certain scenarios. This reflects the prevalent 20th-century practice in orthopedics of immortalizing influential figures through named tests, as seen with the for meniscal pathology developed by Thomas Porter McMurray in the 1940s.