Due to the extreme amount of stresses applied on the knee during sports participation, it is one of the most frequently injured
joints in the body.
For this reason, it is of utmost importance for the clinician to be able to properly evaluate and diagnose injuries related
to the knee.
It is imperative for the clinician’s evaluation and diagnosis to be based on examination of the patient in several different
positions, including standing (anterior, posterior, and lateral), sitting (anterior and lateral), lying (supine, prone, and
lateral decubitus), as well as dynamically (squatting, jumping, walking, and cutting).
In traditional clinical practice, the most common position in which the knee is examined is supine, while many other positions,
specifically the prone position, are often neglected. A number of relevant clinical findings that might otherwise be incompletely
assessed—Baker’s cysts, distal hamstring and proximal calf muscle strains, meniscal injuries, quadriceps flexibility, and
anterior cruciate ligament (ACL) injuries—may be best evaluated through the prone physical examination.
For many years, the best clinical test to evaluate the ACL nonoperatively was considered to be the anterior drawer test. In
later years, it became apparent that false negative anterior drawer signs were extremely common.
In 1976, Torg et al
described the Lachman test, which is more reliable than the anterior drawer and is the standard test for diagnosing ACL-deficient
In a research study of 85 patients, Katz and Fingeroth
concluded that the anterior drawer was 40.9% sensitive and the Lachman test was 81.8% sensitive in determining ACL tears.
Other research shows that the anterior drawer test missed >50% of ACL injuries.
These and other research studies
have led to the general acceptance that the Lachman test is the most accurate test for determining the integrity of the ACL.
Although usually accurate, this test, in certain instances, presents the clinician with some difficulties in both performance
This article provides clinicians with a detailed discussion of a modified clinical test to enhance the evaluation of patients
with suspected ACL injuries. We will expand on the feasibility, technique, and efficiency of performing the Lachman test in
the prone position. Draper and Schulthies
have referred to this specific test as the “alternate” Lachman as compared to the traditional supine position.
Several other alternate variations have been reported for performing the traditional Lachman in the supine or modified supine
position, such as thigh-assisted, support-assisted, tableside, table end, drop leg and axillary cradling.
Due to these and possible other alternate Lachman tests, for clarification, we will refer to the Lachman test performed in
the prone position as the prone Lachman. The Lachman performed in the supine position will be referred to as the traditional
Examination of the uninjured knee is essential to establish a standard to which the contralateral knee can be compared. The
uninjured knee is considered the baseline for the endpoint and anterior tibial translation. This practice allows the clinician
to gain the patient’s confidence by demonstrating the examination components.
The traditional Lachman requires that the patient lie completely relaxed and supine on a firm examination table, with hands
resting across the chest. The knee is passively flexed 10° to 30°, and the quadriceps and hamstring muscles must remain relaxed.
Due to normal anatomical variances among patients, the Lachman may be more or less revealing at a variety of angles between
10° and 30° of flexion. Therefore, it is prudent to repeatedly perform the Lachman at varying degrees of flexion.
has discussed the importance of the clinician standing on the side of the knee to be assessed. While facing the knee, the
clinician places the hand closest to the patient’s pelvis (proximal hand) on the lateral aspect of the distal femur with fingertips
on the posterior femoral shaft and the thumb on the anterior femoral shaft just above the patella (Figure ). The hand closest to the foot (distal hand) is then placed medially on the proximal tibia. The thumb should be placed on
the anteromedial shaft of the tibia, just medial to the tibial tubercle, with the fingers centered posteriorly behind the
tibia. While stabilizing the femur with the proximal hand, the clinician applies an anterior force with the distal hand in
an attempt to translate the tibia anteriorly on the femur.
Figure 1:. The Traditional Lachman Requires the Examiner to Lift the Distal Thigh, Stabilize It, and Simultaneously Apply an Anteriorly
Directed Force to the Proximal Tibia.
With attention directed to the joint line, the amount of anterior tibial translation as compared to the contralateral knee
is noted. More importantly, the presence or absence of a firm endpoint or end-feel is assessed as the point of maximal anterior
tibial translation is reached. The lack of a firm endpoint, regardless of the degree of anterior tibial translation, is usually
indicative of an ACL injury. Specifically, a less-than-firm, solid endpoint (but not completely soft, boggy, or mushy) might
indicate a partial tear, whereas a complete absence of firmness (ie soft, boggy, or mushy) indicates complete ACL disruption.
A firm endpoint is caused by an intact ACL restricting this anterior translation.
As with the traditional Lachman, the uninvolved knee should be evaluated first to establish a guideline by which the contralateral
knee may be judged.
The prone Lachman requires the patient to lie on a firm examination table in the prone position with the lower extremity
fully relaxed. Standing on the involved side and facing the knee, the clinician then places the hand closest to the foot (distal
hand) on the anterior proximal tibia with the index and long finger placed on both sides of the patella tendon resting on
the anterior joint line (Figure ). Using the same arm, the clinician cradles the lower leg in a relaxed position of 10° to 30° of knee flexion (Figure ). An alternative method with the same effect involves the clinician placing his or her distal thigh with knee flexed under
the patient’s shin to support the patient’s lower leg (Figure ). Again, it is important to assess the knee at varying degrees of knee flexion due to the normal anatomical variances in
the patient population. If the clinician’s thigh is supporting the patient’s lower leg, the clinician may move his or her
thigh closer or farther away from the patient’s knee to increase or decrease the angle of knee flexion, respectively. The
heel of the clinician’s other hand (proximal hand) is placed over the posterocentral aspect of the proximal tibia with the
fingers lightly resting on the medial gastrocnemius.
Figure 2:. For the Prone Lachman, the Index and Long Fingers Should Be Placed on Both Sides of the Patella Tendon with the Fingertips
Resting on the Anterior Joint Line..
Figure 3:. The Examiner’s Forearm May Be Used to Provide the Appropriate Knee Flexion Angle While Cradling the Patient’s Relaxed Leg.
Both Hands Are Used to Provide and Guide the Anterior Force and to Interpret the Amount of Translation and the Firmness of
Figure 4:. The Examiner’s Thigh Is a Practical Alternative to Support the Patient’s Relaxed Leg During the Prone Lachman Test. The Examiner
May Adjust the Patient’s Knee Flexion Angle by Varying the Position of the Supporting Thigh.
The heel of the proximal hand is used to direct an anterior force on the posterior tibia, while the fingers of the distal
hand apply a slight back-pressure and simultaneously palpate the amount of anterior tibial translation relative to the femur.
Again, it is important for the clinician to note the presence or absence of an endpoint with maximal anterior tibial translation
as compared to the unaffected leg.
The traditional Lachman presents the clinician with some difficulties in performance and interpretation, whereas the prone
Lachman assists in reducing these difficulties and aids in an enhanced clinical examination (). In performing the Lachman examination, three general challenges must be overcome by the clinician: patient relaxation,
which includes comfort and lower extremity relaxation; psychomotor performance, which includes hand placement, knee position,
knee stabilization, and application of force; and interpretation of the physical examination.
Table. Advantages of the Prone Lachman Versus the Traditional Lachman
To minimize patient apprehension and subsequent muscular tension, the patient should be in the most comfortable position that
minimizes muscular activity while maintaining the appropriate degree of knee flexion. We have noted through clinical practice
that generally patients are more relaxed in the prone rather than the supine position, perhaps due in part to the decreased
visual input that occurs during the prone examination.
With the traditional Lachman, the hip is flexed 20° to 30°, lengthening the hamstrings and inadvertently causing more active
and/or passive tension—resulting in less relaxation. Conversely, the prone Lachman allows the hip to remain in neutral, resulting
in decreased passive hamstring muscular tension.
As mentioned previously, it is desirable to repeat the Lachman at varying knee flexion angles and increased overall relaxation.
Performing the traditional Lachman at varying degrees of flexion results in the hip and knee angles changing each time, whereas
the prone Lachman allows for knee angle changes with the hip being maintained in the neutral position. Avoiding hip angle
changes allows greater control and reproducibility of specific knee angles to be tested and may enhance patient comfort and
With the traditional Lachman, the clinician must stabilize the distal femur in an elevated position against gravity with the
hip slightly flexed. As a result, the patient may subconsciously, through muscular activation in the lower extremity, attempt
to assist the clinician in the maintenance of this position, which is counterproductive. In the prone Lachman, the patient’s
thigh is relaxed and secure on a firm examination table, which decreases the potential for subconscious muscular activation.
It is the clinician’s responsibility to assess and subsequently ensure that the lower extremity musculature, particularly
the hamstrings, are as relaxed as possible. This can be done both manually and visually in either the supine or prone position,
but the prone position allows the clinician better visualization of the entire hamstring group and easier access for manual
assessment of hamstring muscular tension.
Additionally, the traditional Lachman is difficult to perform if the clinician has small hands and/or if the patient has a
relatively large lower extremity.
To adequately stabilize the femur, the clinician’s hands must be able to maintain the thumb over the anterocentral aspect
of the distal femur while reaching around the soft tissue of the thigh far enough with the index and long finger to maintain
position over the posterocentral aspect of the distal femur. Likewise, the thumb of the other hand must be able to maintain
stability over the flat part of the anteromedial tibia while the fingers line up behind the index finger located on the posterocentral
aspect of the tibia. In essence, the clinician is attempting to reach through the soft tissue and grasp the bones for stability
and translation purposes. This must be accomplished without causing a reactive muscular contraction from soft tissue discomfort.
The size of the clinician’s hand and patient’s lower extremity is irrelevant with the prone Lachman. The clinician is only
required to place the heel of his or her hand on the posterior tibia while the other hand is on the anterior tibia with the
index and middle fingers straddling the patella tendon. Additionally, the traditional Lachman, due to its supine position,
requires the clinician to gather up the suspended soft tissue of the posterior calf musculature before being able to apply
an anterior translatory force on the posterior tibia. With the prone Lachman, the calf musculature is already flattened to
some extent due to gravity pulling the soft tissue medially and laterally, thereby reducing the amount of soft tissue the
clinician has to manage in applying an anterior translatory force to the posterior tibia.
In terms of patient relaxation, the prone Lachman allows the hand pressure required for stabilization and force application
to be dispersed over a wider surface area, potentially decreasing reactive muscular contraction.
The traditional Lachman requires that the clinician actively maintain the knee in the desired flexion angle by lifting up
the distal femur. When performing the prone Lachman, the clinician only has to support the patient’s lower leg with his or
her forearm (or thigh) to maintain the desired knee flexion angle, which is significantly less demanding on the clinician.
During the traditional Lachman, the clinician must apply two forces. The first force must be a stabilizing force directed
at the distal femur to prevent upward movement. The second force is a distracting force on the proximal tibia directed against
gravity. These multidirectional components of the procedure can cause psychomotor confusion for the clinician. This confusion
leads to forces other than those of a pure anterior/posterior nature being applied to the knee. The clinician must be capable
of generating enough force to both lift the proximal lower leg against gravity and translate it anteriorly when performing
the traditional Lachman.
With the prone Lachman, the clinician applies an anterior translatory force, which is assisted by gravity. More significantly,
if meniscal tears are present, anterior translation can be blocked, leading to a false negative test. The clinician has the
advantage of overcoming all of these force application challenges with the prone Lachman, which generates a greater amount
of anterior translatory force. The prone Lachman allows the examination table to be used to support and stabilize the thigh;
therefore, the clinician is free to use both hands in a concerted effort to apply one gravity-assisted force to the posterior
Interpretation of the traditional Lachman is accomplished through visualization of the amount of anterior translation in combination
with the proprioceptive feel of the end-point through the hands on the distal femur and proximal tibia. By using hands on
both the anterior and posterior tibia, the clinician performing the prone Lachman can, perhaps, better appreciate the proprioceptive
end feel while still being able to visualize the amount of anterior translation. The fingertips of the index and long fingers
on the anteromedial joint line add the dimension of direct palpation of the anterior translation.
Draper and Schulthies
suggest that when performing the traditional Lachman on a patient with a damaged posterior cruciate ligament, the clinician
can get a false positive test. A torn posterior cruciate ligament (PCL) allows the tibia to sag posteriorly on the femur;
therefore, when the clinician performs the traditional Lachman, the tibia moves forward an excessive amount as compared to
the uninvolved knee, giving the false impression of an ACL tear. Excessive posterior sag in the presence of a PCL tear is
eliminated with the prone Lachman due to gravity pulling the tibia anteriorly.
Conversely, it can be postulated that an ACL tear would result in an anterior sag while being positioned prone and possibly
lead to misinterpretations of the prone Lachman. We have not encountered this problem in our clinical experience, nor has
this been revealed through a search of the literature. In either case, the quantity of true abnormal anterior translation
is an important determinant of injury to the ACL, but the most critical factor is the true quality of the endpoint.
In cases of severe medial instability, positioning of the hand on the medial tibia combined with translatory forces may result
in tibial external rotation on the femur,
giving a false positive translation and lack of a firm endpoint. This problem is easily corrected in the prone Lachman. While
applying an anterior force, the clinician may use both hands to maintain the tibia in the neutral position,
reducing the likelihood of a false positive test caused by external tibial rotation.
A detailed discussion of a modified clinical test to enhance the evaluation of patients with suspected ACL injuries has been
provided. Certainly, the traditional Lachman, when performed correctly, is a reliable and accurate test for determining the
status of the ACL in many patients.
This article presents the prone Lachman in precise detail with its many clinical advantages as compared to the traditional
Lachman. In cases that otherwise may be difficult to appreciate ACL integrity with traditional Lachman testing, the prone
Lachman is a useful adjunct to clinicians for obtaining a more accurate and complete assessment of the ACL. With practice
on both normal and ACL-injured knees, this technique is easily mastered and will enhance any healthcare professional’s examination
of the knee.
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Advantages of the Prone Lachman Versus the Traditional Lachman
||1. Hip flexed 20°–30°.
||Hip is maintained in neutral position.
||Hamstrings more relaxed, less active/passive restraints to anterior translation.
|2. Patient supine.
||Patient generally more relaxed/decreased visual input to patient.
|3. Hamstring relaxation/tension assessed primarily through palpatory means.
||Hamstring relaxation/tension can be more easily assessed through both palpatory and visual means.
||Adds another dimension to ensure patient relaxation.
|4. Patient may subconsciously activate hip flexors to assist clinician in maintaining the hip-flexed/femur elevated position.
||Patient’s thigh is fully supported on a firm table, thereby decreasing potential for muscular activity.
||Further enhances or ensures patient relaxation.
|5. Knee and hip angles both have to be adjusted to assess the endpoint at several angles between 10° and 30°.
||Only knee angles have to be adjusted.
||Less patient movement and resultant discomfort, which reduces potential apprehension.
||6. Clinician pulling against gravity.
||Clinician pushing with gravity.
||Clinician can use gravity to assist in application of anterior force.
|7. Clinician holding/stabilizing femur with one hand.
||Table supporting/stabilizing femur.
||Table can provide more desirable stabilization than the clinician.
|8. Clinician pulling with one hand.
||Clinician uses both hands in concert to provide force application.
||Greater generation of force may be used for less psychomotor confusion for the clinician.
|9. Requires the clinician to apply a stabilizing force and an anterior translatory force.
||Requires clinician to apply only a translatory force.
||Less psychomotor confusion for the clinician.
|10. Difficult with large patients.
||Patient size not a substantial factor.
||Can be used universally on essentially all patients.
|11. Difficult with small hands.
||Hand size not a substantial factor.
||Can be used by all clinicians regardless of hand size.
|12. Undesired tibial movement and lifting off of the table may occur.
||Entire tibia may be stabilized more through cradling in the forearm or on the clinician’s thigh.
||Greater precision of desired translation can be accomplished with fewer extraneous movements.
|13. Soft tissue of calf musculature has to be gathered before actual anterior translation of tibia can occur.
||Soft tissue of calf musculature is already flattened and translated medially and laterally due to gravity.
||Less soft tissue to manage in process of generating anterior tibial translation.
||14. May be difficult to generate enough force to anteriorly translate the tibia past a meniscal tear.
||More anterior force may be generated.
||Potential meniscal blocking may be over-come with additional force.
|15. Anterior displacement is assessed visually. Endpoint is assessed proprioceptively through the clinician’s hands.
||Anterior displacement may be assessed through both visual and palpatory means. Endpoint may be better appreciated proprioceptively
through both hands.
||Enhances one dimension and adds another assessment dimension for the clinician.
|16. PCL-deficient knees may be interpreted falsely as positive for ACL injury due to excessive anterior translation from posterior
||Gravity does not pull the tibia posteriorly.
||Effectively reduces the likelihood of a false positive test by testing only pathological anterior translation.
|17. In cases of severe medial instability, positioning of the hands on the tibia and the translatory forces may result in
tibial external rotation.
||Both hands may be used to maintain the tibia in neutral rotation.
||Effectively reduces the likelihood of a false positive test by testing only anterior translation instead of anteromedial translation.
Clinical examination of the knee to determine the presence of ACL injury presents a challenge to many clinicians. The prone
Lachman test offers many advantages in enhancing patient relaxation, improving psychomotor proficiency, and improving the
clinician’s interpretation of the results.