Key words
Posterior Knee, Lachman Test, Pivot Shift Test, POSTERIOR CRUCIATE TESTING, Posterior Drawer Test, Quadriceps Active Test, Collateral Ligament Tests, Valgus and Varus Stress Tests, Patellofemoral Pain Examination, Patellofemoral Grinding Test, Clarke’s Sign, Patellar Apprehension Test, Passive Patellar Tilt Test, Tilt Test is as follows, Patellar Glide Test, Lateral Step Down Test, Meniscal Tears
Introduction
The knee is particularly susceptible to traumatic injury because of its vulnerable location midway between the hip and the ankle, where it is exposed to the considerable forces transmitted from the ground through the knee to the hip. Thorough examination of all of the knee structures, including the ligaments and menisci, should be included in every knee evaluation. The examiner must rely on numerous physical exam maneuvers to evaluate these structures. It is crucial not only that these maneuvers are performed correctly but also that the examiner is aware of the sensitivity and specificity of the various tests, as well as the limitations of the tests, to make the most accurate diagnosis possible. In this chapter, we provide a review of the physical examination of the knee followed by a literature-based review of the diagnostic accuracy of the major provocative tests used to diagnose knee injuries.
Inspection
Assessment of the knee should begin with an overall evaluation of lower extremity alignment. Varus–valgus alignment of the lower extremity while weight bearing with the knee in full extension should be noted. Normally, the tibia has a slight valgus angulation compared with the femur, and this angle is usually more pronounced in females. From the side, the knee should be fully extended when the patient is standing. Slight hyperextension of the knee is a normal finding, provided that it is present in both lower extremities. The position of the patella should be noted. When viewing the patella, the examiner should note whether the patella points straight ahead, tilts inward or outward, or is rotated in any way. Rotation and tilt may be caused by tight structures in the lower extremities that alter the position of the patella.
The skin around the knee joint should be inspected for any bruising, abrasions, lacerations, or surgical scars. External signs of injury can give a clue as to the mechanism of injury and internal structures damaged. Signs of swelling in the knee should be observed and may be suggested by the loss of the peripatellar groove on either side of the patella. Generalized swelling may be due to an effusion in the joint, whereas localized swelling may be due to a distended bursa or cyst.
The quadriceps muscle atrophies quickly when there is any type of knee joint pathology. Signs of muscular atrophy should therefore be observed and quantified with circumferential measurements that compare the affected and unaffected sides for differences in muscle girth.
Assessment of gait is an integral component of the comprehensive knee examination. In the traditional, heel-striker gait cycle, the knee comes to full extension only at heel strike. During stance phase, slight flexion occurs, and it is the contraction of the quadriceps at this point that prevents giving way. At toe-off, the knee flexes to about 40 degrees and continues to flex through midswing to approximately 65 degrees. At this point, the quadriceps contract to begin acceleration of the leg, with the knee returning to full extension again at heel strike. At heel strike, the hamstrings must contract in order to decelerate the leg. Abnormalities in gait pattern can occur from various causes. Weak hamstrings may not decelerate the knee properly and result in hyperextension at heel strike. Weakness in the quadriceps can cause a hard heel strike to occur, with excessive hip extension to force the knee into a hyperextended position to prevent buckling. Ligament injuries may result in a varus or valgus thrust or even a buckling of the joint, depending on the extent of the ligament compromise. Finally, pain within the knee joint may cause the patient to walk with an antalgic gait.
Range of Motion
Active and passive range of motions (ROMs) of the knee should be measured. The neutral position (0 degrees) for the knee joint occurs when the femur and tibia are in a straight, fully extended position. Positive degrees of motion are measured for flexion, and negative degrees of motion are used to describe hyperextension of the knee. Normal ROMs are typically 135 degrees of flexion and as much as 5 to 10 degrees of hyperextension. Given the significant amount of normal individual variation, it is very important to compare the involved and uninvolved sides when determining normal motion for an injured individual.
As the examiner moves the knee through flexion and extension, the movements of the patella as it tracks along the femoral trochlea should be observed. The patella does not follow a straight path as the knee moves but instead follows a curved pattern. The examiner should note whether the patella tilts laterally, tilts anteroposteriorly, or rotates during dynamic knee extension. The examiner should also observe for signs of quadriceps lag, which results from weakness of the quadriceps muscle and causes the patient to have difficulty in completing the last 10 to 15 degrees of knee extension. Although the majority of motion occurs with extension and flexion, the knee does possess the ability to rotate both internally and externally and does so normally as part of the “screw-home” mechanism of full extension. Approximately 10 degrees of rotation in either direction is thought to represent a normal range; significant increases in internal or external rotation may indicate ligament compromise.
Passive ROM testing is particularly useful when the patient is not able to perform the full range of active movements. Flexion is tested with the patient lying prone. The leg is held just proximal to the ankle, and the knee is flexed. There are a number of causes for a decrease in ROM at the knee. The most common cause is an effusion within the knee joint. A large meniscus tear or other intra-articular loose body can act as a mechanical block, preventing full motion of the knee. Osteoarthritic changes can also reduce knee motion, typically with flexion being less affected than extension. On the other hand, significant ligamentous injuries can undermine the normal knee restraints and allow an abnormally increased range of knee motion.
Palpation
The entire knee should be palpated in a sequential manner and compared with the uninjured side. The presence of an increase in temperature of the skin overlying the joint should be determined before other tests are performed. The skin over the noninflamed knee is typically cooler than the skin overlying surrounding musculature because of the relatively avascular nature of the knee joint. Palpation is the best way to determine the presence of swelling in and around the knee joint. A large joint effusion will be obvious to the examiner, whereas a small effusion can be identified by placing gentle thumb pressure over the lateral aspect of the patellofemoral joint and detecting a fluid wave with the index finger. In the ballottement test, one hand milks fluid from the suprapatellar pouch while the other hand presses down on the patella. The patella’s springing back indicates the presence of a larger effusion.
Localized tenderness is helpful in pinpointing the site of injury or pathology in the knee joint. A detailed knowledge of the bony and soft tissue surface anatomy is therefore of critical importance when trying to make a specific diagnosis in the knee. Palpation of the bony and soft tissue structures of the knee can be divided into four quadrants: medial, lateral, anterior, and posterior.
Medial Knee
Bony Structures
The bony structures of interest in the medial aspect of the knee include the medial tibial plateau, tibial tubercle, medial femoral condyle, medial femoral epicondyle, and the adductor tubercle. The examiner’s thumbs are placed on the anterior portion of the knee and pressed into the soft tissue depressions on each side of the infrapatellar tendon. Pushing a thumb slightly inferiorly into the soft tissue depression, the examiner palpates the distinct upper edge of the medial tibial plateau. The medial tibial plateau represents one site of attachment for the medial meniscus. Next, the infrapatellar tendon may be followed distally to its insertion into the tibial tubercle. Moving the thumb superior from the starting position in the depressions on each side of the infrapatellar tendon, the medial femoral condyle will become palpable. The femoral condyle is more easily palpated if the knee is flexed to greater than 90 degrees. The adductor tubercle is located on the posterior medial aspect of the medial femoral condyle. It can be located by moving the thumbs posteriorly from the medial surface of the medial femoral condyle.
Soft Tissue Structures
Palpation of the medial meniscus is performed along the medial joint line. The medial edge of the medial meniscus becomes more prominent when the tibia is internally rotated. Tears of the posteromedial portion of the medial meniscus are the most common and are diagnosed clinically in part by the finding of tenderness at the posteromedial corner of the knee. The medial collateral ligament (MCL) is a broad ligament that spans from the medial femoral epicondyle to the tibia. Historically believed to be a relatively straightforward stabilizer against valgus stress, recent anatomic dissections show that the MCL has a deep and superficial layer that performs distinct functions. The superficial MCL attaches to the medial femoral epicondyle proximally and the medial aspect of the tibia distally, approximately 4 cm below the level of the joint line. The superficial MCL is the primary restraint against valgus forces at all angles of knee flexion. The deep fibers of the MCL represent a thickening of the middle third of the joint capsule. The deep MCL is a primary stabilizer of the medial meniscus and functions as a rotational constraint for the tibiofemoral joint. It consists of two subligaments, the meniscofemoral ligament (attaching the medial meniscus to the femur) and the meniscotibial ligament (attaching the medial meniscus to the tibia). Given the complex substructure of the MCL complex, the entire region of the MCL ligament should be palpated from origin to insertion for tenderness.
On the posteromedial side of the knee, the tendons of the sartorius, gracilis, and semitendinosus muscles cross the knee joint and insert into the lower portion of the medial tibial plateau. The pes anserine bursa lies at the common insertion of these muscles and may become a source of pain when the bursa is inflamed ( Fig. 9.1 ).
Lateral Knee
Bony Structures
The bony structures of interest in the lateral aspect of the knee include the lateral tibial plateau, lateral tubercle (Gerdy tubercle), lateral femoral condyle, lateral femoral epicondyle, and head of the fibula. Starting with your thumb in the soft tissue depression just lateral to the infrapatellar tendon, the edge of the lateral tibial plateau can be palpated inferiorly. The lateral tubercle is the large prominence of bone palpable just below the lateral tibial plateau. Moving upward and laterally from the starting point of the depression, the lateral femoral condyle becomes palpable. More of the lateral femoral condyle is palpable when the knee is flexed to greater than 90 degrees. Finally, the fibular head is easily palpable along the lateral aspect of the knee, inferior to the joint line, at about the level of the tibial tubercle.
Soft Tissue Structures
Palpation of the lateral meniscus is performed along the lateral joint line, with the knee in a slightly flexed position ( Fig. 9.2 ). The lateral meniscus is attached to the popliteus muscle and not the lateral collateral ligament (LCL). The LCL is a palpable cord that runs between the lateral femoral condyle and the fibular head ( Fig. 9.3 ). Also inserting on the fibular head is the biceps femoris tendon. The major portion of the biceps femoris inserts deep to the LCL on the lateral fibular head, while a smaller slip of the biceps femoris inserts superficial to the LCL. Thus, at the fibula, the LCL can be palpated as it is “sandwiched” between fibers of the biceps femoris tendon. Additionally, the iliotibial band can be assessed for tenderness at its insertion point on the Gerdy tubercle of the tibia and as it crosses the lateral condyle of the femur. Complaints of “snapping” over the lateral femoral condyle are often associated with a tight iliotibial band. The common peroneal nerve can be palpated as it wraps around the fibula, and the nerve may be assessed for a positive Tinel’s sign, indicative of nerve irritation or damage.
Anterior Knee
Bony Structures
The bony structures of interest in the anterior knee are the patella and the trochlear groove of the femur. The trochlear groove can be palpated by placing your thumbs over the medial and lateral joint lines and moving upward along the two femoral condyles. The depression of the trochlear groove is palpated in the midline, above the level of the patella. In flexion, the patella is fixed in the trochlear groove and therefore the undersurface of the patella is not easily palpated. In extension, the patella is more mobile, and palpation of the medial and lateral undersurfaces (facets) of the patella is possible in this position.
Soft Tissue Structures
In the anterior aspect of the knee, an assessment of the tone and bulk of the quadriceps muscle should be made because this is the main stabilizing muscle for the knee. Quadriceps strength along with gluteal and core muscular function are important areas along the kinetic chain that are important to evaluate as part of the assessment of the patellofemoral joint. The prepatellar bursa overlies the anterior aspect of the patella ( Fig. 9.4 ). Thickening or swelling of the prepatellar bursa is commonly seen in people who frequently kneel. The patellar tendon is the continuation of the quadriceps tendon from the lower pole of the patella to the tibial tubercle. The superficial infrapatellar bursa lies between the skin and the patellar tendon and is easily palpable on exam. The deep infrapatellar bursa lies beneath the patellar tendon.
Posterior Knee
The posterior fossa is bounded by the hamstring tendons proximally and the two heads of the gastrocnemius muscle distally. Passing through the posterior fossa are the tibial nerve, the popliteal artery, and the popliteal vein. Examination of the popliteal pulse is best performed with the knee in 90 degrees of flexion, so that the hamstring and calf muscles are relaxed. The popliteal artery is the deepest structure in the posterior fossa and travels against the joint capsule. The posterior tibial nerve is the most superficial structure in the popliteal area, with the popliteal vein running directly beneath it. A cystic swelling within the fossa, called a Baker cyst, can present as a usually painless, mobile swelling on the medial side of the fossa. Many Baker cysts directly communicate with the joint. The cyst is an enlargement of the normal gastrocnemius–semimembranosus bursa.
The quadriceps muscle is the primary extensor of the knee and is innervated by the femoral nerve, with primarily L3 and L4 nerve root innervation. Manual testing of the quadriceps muscle can be performed with the patient in the sitting position. The patient should be asked to extend the knee actively. The examiner can use one hand to resist the extension of the leg, while using the other hand to palpate the tone and bulk of the muscle as it is contracting. The primary flexors of the knee are the hamstring muscles, which include the semimembranosus, semitendinosus, and biceps femoris. All of the hamstring muscles are innervated by the tibial portion of the sciatic nerve. The semimembranosus and semitendinosus receive the majority of their innervation from the L5 nerve root, while the biceps femoris receives most of its innervation from the S1 nerve root.
Manual testing of the hamstrings as a group can be performed by having the patient lie prone on the examination table. The patient is instructed to flex his or her knee while you resist this motion by holding the leg just proximal to the ankle joint. The patellar tendon reflex is a deep tendon reflex involving the L2, L3, and L4 neurologic levels, but for clinical application, it is primarily considered an L4 reflex. Sensation should also be assessed in the area of the knee and surrounding areas. Peripheral pulses should be tested in the femoral, popliteal, dorsalis pedis, and posterior tibial arteries. Historically, the incidence of popliteal artery injury following knee dislocation was reported as high as 25%. More recent and more carefully controlled studies place the rate of arterial injury following knee dislocation between 1.3 and 18% ; however, unrecognized vascular injury may result in catastrophic outcomes. Hence, assessment of vascular system integrity is crucial with all acute knee injuries.
The ligaments of the knee joint are the primary structures responsible for maintaining stability of the joint ( Fig. 9.5 ). The knee should be checked for stability in the anteroposterior, medial–lateral, and rotatory directions. It is important to compare tests for stability with the normal contralateral knee, since there can be individual variation in the laxity of the ligaments tested. It can be helpful to evaluate the uninjured knee first, so that the patient has an understanding of what manipulations are going to be performed. In the acute situation, when the mechanism of injury is observed and the patient can be evaluated immediately before pain, guarding, and secondary muscle spasm occur, the assessment of the ligaments can be much easier. Specific tests to assess the anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), LCL, and MCL are described in the following sections, along with a literature review of the sensitivity and specificity of the individual tests.
Tests for the Anterior Cruciate Ligament
The ACL is one of the main stabilizers of the knee with injury often resulting in significant disability. Three of the most commonly applied tests are the anterior drawer test the Lachman test, and the pivot shift test ( Table 9.1 ). The lever sign test or Lelli test is a new test proposed to evaluate ACL injury.
| Test | Review | Reliability/Validity Tests | Comments |
|---|---|---|---|
| Anterior drawer test | The subject is supine, hip flexed to 45 degrees and knee flexed to 90 degrees. The examiner sits on the subject’s foot, with hands behind the proximal tibia and thumbs on the tibial plateau. Anterior force is applied to the proximal tibia. Hamstring tendons are palpated with index fingers to ensure relaxation. Increased tibial displacement compared with the opposite side is indicative of an ACL tear. | Harilainen 1987 Sensitivity: 41% Sensitivity (under anesthesia): 86% | Prospective study of 350 acute knees evaluated with 79 arthroscopically confirmed acute ACL injuries. |
| Katz and Fingeroth 1986 Sensitivity: 22.2% (acute) Sensitivity: 53.8% (chronic) Specificity: >95% (acute + chronic) | Testing performed only under anesthesia. Retrospective study of limited sample size: 9 acute ACL injuries and 12 chronic. | ||
| Jonsson et al. 1982 Sensitivity: 33% (acute) Sensitivity: 95% (chronic) | All 107 patients had documented acute or chronic ACL ruptures. Specificity was not assessed since only positive ACL ruptures were included. | ||
| Donaldson et al. 1985 Sensitivity: 70% (acute) Sensitivity: 91% (under anesthesia) Specificity: Not reported | A retrospective study that was not designed to evaluate specificity since it was a review of only positive cases. | ||
| Mitsou and Vallianatos 1988 Sensitivity: 40% (acute) Sensitivity: 95.2% (chronic) Specificity: Not reported | Of 144 knees, 60 had acute injuries all assessed within 3 days of injury. In the group of 80 chronic injuries, the 4 false-negative drawer tests were associated with bucket-handle tears. | ||
| Kim and Kim 1995 Sensitivity (under anesthesia): 79.6% Specificity: Not reported | Testing performed only under anesthesia . Retrospective study. All ACL injuries were chronic. | ||
| Lachman test | The patient lies supine. The knee is held between full extension and 15 degrees of flexion. The femur is stabilized with one hand while firm pressure is applied to the posterior aspect of the proximal tibia in an attempt to translate it anteriorly. | Torg et al. 1976 Sensitivity: 95% Specificity: Not reported | A study of 93 knees with combined tears of the ACL and median meniscus. All 5 false negatives were associated with bucket-handle tears of the meniscus. |
| Donaldson et al. 1985 Sensitivity: 99% Specificity: Not reported | A retrospective study that was not designed to evaluate specificity since it was a review of only positive cases. | ||
| Katz and Fingeroth 1986 Sensitivity (under anesthesia): 84.6% Specificity (under anesthesia): 95% | Testing performed only under anesthesia. A retrospective study of limited sample size: 9 acute and 12 chronic ACL injuries. | ||
| Kim and Kim 1995 Sensitivity (under anesthesia): 98.6% Specificity: Not reported | Testing performed only under anesthesia. Retrospective review study of ACL injuries all of which were chronic. | ||
| Mitsou and Vallianatos 1988 Sensitivity: 80% (acute) Sensitivity: 98.8% (chronic) | Of 144 knees, 60 had acute injuries all assessed within 3 days of injury. | ||
| Jonsson et al. 1982 Sensitivity: 87% (acute) Sensitivity: 94% (chronic) | All 107 patients had acute or chronic ACL injuries. Specificity was not assessed since only positive ACL ruptures were included. | ||
| Pivot shift test | The leg is picked up at the ankle. The knee is flexed by placing the heel of the hand behind the fibula. As the knee is extended, the tibia is supported on the lateral side with a slight valgus strain. A strong valgus force is placed on the knee by the upper hand. At approximately 30 degrees of flexion, the displaced tibia will suddenly reduce, indicating a positive pivot shift test result. | Lucie et al. 1984 Sensitivity: 95% Specificity: 100%* | Fifty knees were tested. *There was not an adequate sample of intact ACLs to determine specificity. |
| Katz and Fingeroth 1986 Sensitivity: 98.4% Specificity >98% | Testing performed only under anesthesia. A retrospective study of limited sample size: 9 acute and 12 chronic ACL injuries. | ||
| Donaldson et al. 1985 Sensitivity: 35% Sensitivity (under anesthesia): 98% Specificity: not reported | A retrospective study that was not designed to evaluate specificity since it was a review of positive cases. | ||
| Lever Sign test | The patient is placed supine with the knees fully extended. The examiner places a closed fist under the proximal third of the calf. Moderate downward force to the distal third of the quadriceps is applied with the other hand. In the intact ACL, the heel rises up off of the table. With a partially or completely ruptured ACL, the heel is pulled down to the exam table. | Lelli et al. 2014 Reported 100% agreement with MRI findings of complete or partial rupture. | A single case series of 400 knees. |
Anterior Drawer Test ( 
)
Although the anterior drawer test has been widely used in the diagnoses of ACL ruptures, the origin of this maneuver remains obscure ( Fig. 9.6 ). According to Paessler and Michel, as early as 1879, Paul Segund described the “abnormal anterior–posterior mobility” of the knee associated with ACL ruptures. George Noulis, whom Paessler and Michel credited with the earliest description of what we now call the Lachman test, also elucidated the drawer tests in large degrees of flexion. In a translation of Noulis’s 1875 French thesis that appears in the textbook Diagnostic Evaluation of the Knee by Strobel and Stedtfeld, Noulis describes the following test:
[With] the patient’s leg flexed, the thigh can be grasped with one hand at the lower leg with the other hand keeping the thumbs to the front and fingers to the back. If the lower leg is held in this grip and then moved backwards and forwards, it will be seen that the tibia can be moved directly backwards and forwards.
Noulis observed a great deal of tibia displacement when both cruciate ligaments were severed. The assumption that a positive anterior drawer test indicates a tear of the ACL was not commonly accepted until much later. Increased anterior tibial displacement compared with the uninvolved side is now supported as indicative of a tear of the ACL.
There remain some limitations of this test with sensitivities reported between 18% to 92% and specificities between 78% to 98%. A recent meta-analysis illustrates the difference in test characteristics when performed on patients under anesthesia. In an analysis of 20 available studies, the mean sensitivity and specificity of the anterior drawer test were 38% to 81% in awake patients and 63% to 91% in anesthetized patients, respectively. Differences in accuracy of the test are also noted in those with acute versus chronic injury, with the anterior drawer test being more accurate in chronic injury. Anterior drawer results may also be affected by the presence of concomitant injury. Injuries to other secondary stabilizers that typically limit anterior tibial translation (ie, MCL, anterolateral ligament, and medial meniscus) are known to increase the degree of anterior knee displacement caused by the anterior drawer maneuver. These combined observations suggest that the anterior drawer test may become increasingly sensitive as the secondary restraints of anterior stability are lost. As with other tests of anterior stability, the real-world accuracy of the anterior drawer test depends on the expertise of the examiner. The anterior drawer test exhibited only moderate interrater reliability among providers (x = 0.57).
Falsely negative anterior drawer tests in instances of isolated ACL tears may occur secondary to protective spasm of the hamstring muscles and the anatomic configuration of the femoral condyle. Clinical practice shows that false-positive results may occur in the setting of PCL insufficiency in which posterior sagging of the tibia may result in a false sense of its neutral position, resulting in a false sense of excessive anterior translation, when in fact the tibia is moving from a posterior translated position into its normal neutral position.
Given the wide variation in reported sensitivities of the anterior drawer test, especially because performing examinations under general anesthesia is of somewhat limited utility in the clinical setting, examiners should be cautious to not rule out an acute ACL injury based solely on a negative anterior drawer test result. Conversely, because the specificity of the test is quite high, a positive anterior drawer test result would more strongly suggest the presence of ACL pathology.
Lachman Test ( 
)
The Lachman test was described by Joseph Torg, who trained under Dr. Lachman at Temple University. Interestingly, Hans Paessler traced descriptions of what we now call the Lachman test as far back as 1875, when it was described in a thesis by George Noulis in Paris. Despite these very early descriptions, the test was not widely recognized or used until Torg’s classic description in 1976 ( Fig. 9.7 ) :
The examination is performed with the patient lying supine on the table with involved extremity on the side of the examiner. With the patient’s knee held between full extension and 15 degrees of flexion, the femur is stabilized with one hand while firm pressure is applied to the posterior aspect of the proximal tibia in an attempt to translate it anteriorly. A positive test indicating disruption of the anterior cruciate ligament is one in which there is proprioceptive and/or visual anterior translation of the tibia in relation to the femur with a characteristic “mushy” or “soft” end point. This is in contrast to a definite “hard” end point elicited when the anterior cruciate ligament is intact.
Numerous studies have looked at the sensitivity and specificity of the Lachman test, and other studies have compared the accuracy of this test with the original anterior drawer. Torg originally reported that in 88 of 93 (95%) individuals with combined lesions involving the ACL and medial meniscus, the Lachman test result was positive. The false-negative test results were attributed to incarcerated bucket-handle tears blocking forward translation of the tibia. Donaldson and associates noted a sensitivity of greater than 99% for this test and found it to be relatively unaffected by associated ligamentous or meniscal injuries. This was in contrast to the significant variability with the anterior drawer test when tested in those with injury to the secondary restraints of the knee. In a meta-analysis of nine high-quality studies, the sensitivity of the Lachman test ranged from 63% to 93% with a mean value of 86% and a specificity range of 55% to 99% with a mean of 91%. In experienced hands, the Lachman’s test characteristics are relatively unchanged by anesthesia with a sensitivity and specificity of 86% to 91% without and 85% to 95%, respectively, with general anesthesia.
Lachman testing exhibits impressive clinical predictive value. Compared with anterior drawer testing and composite testing, a positive Lachman test result showed a likelihood ratio (LR) of 25.0 (25-fold increased likelihood of ACL injury), while a negative Lachman test result yielded a negative likelihood ratio (−LR) of 0.1. Composite testing (Lachman plus anterior drawer) yielded virtually identical characteristics (+LR 25.0, −LR 0.04), again illustrating the superiority of the Lachman to the anterior drawer. While the pivot shift test (see subsequent section) has a higher composite specificity than the Lachman for ACL injury, these high sensitivities have only been demonstrated in anesthetized patients. In addition, the Lachman test yields consistently higher sensitivity than pivot shift testing in both awake and anesthetized patients. Hence, the Lachman test is the most clinically sensitive and specific test for diagnosis of ACL tear; however, there are certain limitations to the test. Draper and colleagues noted that the Lachman test is not easily performed when the patient has a large thigh girth or the examiner has small hands. Various modifications of the Lachman have been propose including “prone,” “drop leg,” and “stabilized” Lachman tests. Of these modified Lachman maneuvers, only the prone Lachman test has been described in more than a single publication. A handful of publications suggest that the prone Lachman test, originally described by Feagin in 1989, has favorable test characteristics similar to that of the original supine test. The prone Lachman has a reported sensitivity of 71% and a specificity of 97%, with a +LR of 20 and a −LR of 0. A single publication examining reliability of anterior instability tests suggests that the traditional Lachman has the highest intrarater reliability (Cohen’s κ = 1.00), while the prone Lachman has the highest interrater reliability (Cohen’s κ = 0.81).
Pivot Shift Test ( 
)
The pivot shift is both a clinical phenomenon that gives rise to the complaint of giving way of the knee and a physical sign that can be elicited upon examination of the injured knee ( Fig. 9.8 ). Hey Groves in 1920 and Palmer in 1938 both published photographs demonstrating patients voluntarily producing what is called the pivot shift phenomenon. The pivot shift phenomenon was characterized as an anterior subluxation of the lateral tibial plateau in relation to the femoral condyle when the knee approaches extension with reduction produced with knee flexion. The pivot shift phenomenon is enhanced by the convexity of the tibial plateau in the sagittal plane. The pivot shift test was initially described as follows :
The leg is picked up at the ankle with one of the examiner’s hands, and if the patient is holding the leg in extension, the knee is flexed by placing the heel of the other hand behind the fibula over the lateral head of the gastrocnemius. As the knee is extended, the tibia is supported on the lateral side with a slight valgus strain applied to it. In fact, this subluxation can be slightly increased by subtly internally rotating the tibia, with the hand that is cradling the foot and ankle. A strong valgus force is placed on the knee by the upper hand. This impinges the subluxed tibial plateau against the lateral femoral condyle, jamming the two joint surfaces together, preventing easy reduction as the tibia is flexed on the femur. At approximately 30 degrees of flexion, and occasionally more, the displaced tibial plateau will suddenly reduce in a dramatic fashion. At this point, the patient will jump and exclaim, “That’s it!”
Recent meta-analysis of six available studies showed sensitivity ranging from 18% to 48% and an extremely high specificity of 97% to 99%. However, the meta-analysis notes that because of relatively low study numbers and heterogeneous methods (anesthesia vs awake), these studies were not appropriate for pooled meta-analysis. A more recent meta-analysis examining pivot shift testing in awake versus anesthetized patients found wide variations in sensitivity (38% awake, 63% anesthesia) and specificity (81% awake, 98% anesthesia).
The pivot shift is a technically complicated test. Many authors have recommended various modifications on the classic pivot shift test for producing the pivot shift phenomenon, including the addition of hip abduction, knee flexion, and external tibial rotation. Even mechanized pivot shift testing has been proposed in an effort to improve sensitivity and test mechanics. In a recent review of 48 pivot shift testing articles, Arilla and colleagues recommended that a 30-degree knee flexion angle be used along with a 10-Nm valgus torque and a 5-Nm internal rotation torque. Interestingly, Arilla and associates also found that robotic systems were used to interpret the pivot shift test in nearly one in four reported studies and that robotic systems were superior to human examiners in controlling forces during pivot shift testing and interpreting test results. In summary, the bottom line remains the same: the pivot shift is marginally sensitive, especially in awake patients, but highly specific, especially when wielded by an experienced examiner.
Because the specificity is high, the presence of the pivot shift will usually be indicative of an ACL tear. Moreover, the presence of a positive pivot shift test result in a conscious patient may reflect an inability of the patient to protect the knee, which may suggest that these patients are less likely to succeed with nonoperative treatment. Additionally, following ACL reconstructive surgery, the pivot shift test has also been shown to be an excellent indicator of recurrent instability and postoperative outcomes. In a recent systematic review by Ayeni and coworkers, the pivot shift test correlated with final functional outcomes in 85% of the included studies, demonstrating the pivot shift test to be a reliable evaluation of the success of a reconstructive surgery.
Lever Sign Test
A newer test for either full or partial ACL tears is the lever sign or Lelli test. Developed in 2005 by Dr. Alessandro Lelli, the lever sign test is intended to be diagnostic of both partial and complete tears, as well as acute injuries. The lever sign test was originally described as follows :
The patient is placed supine with the knees fully extended on a hard surface such as the examining table. The examiner stands at the side of the patient and places a closed fist under the proximal third of the calf. This causes the knee to flex slightly. With his other hand, he applies moderate downward force to the distal third of the quadriceps. With this configuration, the patient’s leg acts as a lever over a fulcrum—the clinician’s fist. In an intact knee, the creation of a complete lever by the ACL allows the downward force on the quadriceps to more than offset the force of gravity, the knee joint rotates into full extension, and the heel rises up off of the examination table. With a partially or completely ruptured ACL, the ability to offset the force of gravity on the lower leg is compromised and the tibial plateau slides anteriorly with respect to the femoral condyles. In this case, the gravity pulls the heel down to the examination table.
In a single case-series of 400 patients with ACL tears, the Lever Sign test was shown to agree with magnetic resonance imaging (MRI) findings. The lever test result was negative for all uninjured, contralateral knees and positive for all injured knees. This is the only published study on the Lever sign to date. No formal study has investigated the sensitivity and specificity of the test, and no studies have examined its predictive value in an undifferentiated primary care population. Thus, further work clearly is needed, but the lever sign test is quite simple and appears safe to perform on injured and uninjured patients.
Posterior Cruciate Testing
Three commonly used tests for the diagnosis of PCL injuries are the posterior sag sign, the posterior drawer test, and the quadriceps active test. Unlike the ACL, the PCL rupture does not have a definitive test, and the most accurate method of physical examination is still a matter of debate ( Table 9.2 ).
| Test | Review | Reliability/Validity Tests | Comments |
|---|---|---|---|
| Posterior sag sign | The patient lies supine with the hip flexed to 45 degrees and the knee flexed to 90 degrees. In this position, the tibia rocks back, or sags back, on the femur if the PCL is torn. Normally, the tibial plateau extends 1 cm beyond the femoral condyle when the knee is flexed to 90 degrees. If this step off is lost, this step-off test result is considered positive. | Rubinstein et al. 1994 Sensitivity: 79% Specificity: 100% | Double-blinded, randomized, controlled study of 39 subjects (75 knees for analysis). Only included patients with chronic PCL tears. Examiners all fellowship trained in sports medicine with at least 5 years’ experience. |
| Posterior drawer test | The subject is supine with the test hip flexed to 45 degrees, knee flexed to 90 degrees, and foot in neutral position. The examiner sits on the subject’s foot with both hands behind the subject’s proximal tibia and thumbs on the tibial plateau. A posterior force is applied to the proximal tibia. Increased posterior tibial displacement as compared with the uninvolved side is indicative of a partial or complete PCL tear. | Rubinstein et al. 1994 Sensitivity: 90% Specificity: 99% | See text discussion of drawer test |
| Loos et al. 1981 Sensitivity: 51% Specificity: Not reported | Compilation study from registry of knee surgeries in the US and Australia; it included 102 PCL injuries. Multiple examiners at different sites, without indication that study was randomized or controlled. | ||
| Moore and Larson 1980 Sensitivity: 67% Specificity: Not reported | Retrospective study of 20 patients. All false negatives were found to have both ACL and PCL injuries at surgery. | ||
| Hughston et al. 1976 Sensitivity: 55.5% Specificity: Not reported | Review of 54 acute PCL tears studied over a 10-year period. Posterior drawer test was performed under anesthesia. | ||
| Clendenin et al. 1980 Sensitivity 100% Specificity: Not reported | Retrospective study of only 10 patients | ||
| Harilainen 1987 Sensitivity: 90% Specificity: Not reported | Prospective study that included only 9 patients with arthroscopically confirmed PCL tears. | ||
| Quadriceps active test | The subject is supine with the knee flexed to 90 degrees in the drawer test position. The foot is stabilized by the examiner, and the subject is asked to slide the foot gently down the table. Contraction of the quadriceps muscle in the PCL deficient knee results in an anterior shift of the tibia of 2 mm or more. The test is qualitative. | Daniel et al. 1988 Sensitivity: 98% Specificity: 100% | Study included 92 subjects, 25 with no history of knee injury. Study was not blinded or randomized because the examiners were told which knee was the index knee |
| Rubinstein et al. 1994 Sensitivity: 54% Specificity: 97% | Double-blinded, randomized, controlled study of 39 subjects (75 knees for analysis). Examiners all fellowship trained in sports medicine with at least 5 years’ experience. Only included patients with chronic PCL tears. |
Posterior Sag Sign ( 
)
Although it is unclear who coined the term posterior sag sign, Mayo Robson described this phenomenon in 1903. A detailed description of the test as it is performed today follows ( Fig. 9.9 ):
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