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Current Concepts Review : Comprehensive Physical Examination for Instability of the Knee James H. Lubowitz, Brad J. Bernardini and John B. Reid III Am J Sports Med 2008 36: 577 originally published online January 24, 2008 DOI: 10.1177/0363546507312641

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Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 Clinical Sports Medicine Update

Current Concepts Review

Comprehensive Physical Examination for Instability of the Knee

James H. Lubowitz,*† MD, Brad J. Bernardini,†‡ MD, and John B. Reid III,† MD From the †Taos Orthopaedic Institute Research Foundation, Taos, New Mexico, and the ‡South Jersey Center for Orthopedics and Sports Medicine, Vineland, New Jersey

A careful history and physical examination are the cornerstones of orthopaedic sports medicine. When evaluating a patient for ligamentous instability of the knee joint, an understanding of the contribution of anatomic structures to stability enhances a prac- titioner’s ability to achieve an accurate clinical diagnosis. This article reviews the various types of knee instability and the associated anatomic structures. Ultimately, information must be obtained from multiple tests to reach the final diagnosis. We describe in detail the pathologic and biomechanical basis of the tests for both tibiofemoral and patellofemoral instability of the knee joint and provide recommendations for performance and interpretation of these physical examinations. Keywords: knee; instability; examination; diagnosis; anatomy; biomechanics

Effective physical examination is a cornerstone of success- in an age of advanced diagnostic imaging, a careful history ful diagnosis and subsequent treatment of complex knee and effective physical examination continue to serve as the injuries. As a matter of course, all clinical knee examina- foundation of orthopaedic sports medicine. tions should include assessment of range of motion, limb When approaching the patient with a knee injury, attention alignment, and neurovascular status, as well as compari- to the perceived direction of joint instability, mechanism of son with the uninjured knee. Various physical examination injury if known, and symptomatology may offer clues to the tests have been developed that can assist in accurately underlying structure or structures that have been damaged. diagnosing ligamentous and patellofemoral instabilities, although difficulty in performing or interpreting many of these tests merits their thorough description and discus- ANTERIOR INSTABILITY sion. Often, the information obtained from multiple tests The well-recognized primary function of the anterior cruci- may contribute to a final diagnosis. ate ligament (ACL) is to prevent excessive anterior trans- This article reviews the various types of knee instability lation of the tibia relative to the femur. Anterior cruciate and the associated anatomic structures. Because injuries to ligament rupture is epidemic, and as such, a brief consid- more than one structure are common, it is important to con- eration of ACL injury biomechanics is merited. duct a thorough survey of the knee. We also describe physi- The mechanism of injury of the majority of ACL rup- cal examination tests that are based on both biomechanical tures is not related to contact but typically involves abrupt analyses and clinical observations and useful accessory tests deceleration, hyperextension, or pivot on a fixed foot.5,93 that may help confirm a diagnosis. One must also bear in For contact injuries, the typical mechanism of injury is a mind the potential limitations of clinical testing, including blow to the lateral aspect of the knee when the foot is the inability to produce sufficient magnitude of force to sim- planted and is often associated with medial instability or ulate physical activity; reflex resistance on the part of the anteromedial rotatory instability. Patients sometimes patient because of anxiety, pain, or the recruitment of report feeling or hearing a “pop,” are generally unable to dynamic secondary knee stabilizers; and the presence or 83,92 continue sporting activity, and often develop an acute absence of static secondary stabilizers. Although we live hemarthrosis.18 With chronic ACL insufficiency, the knee is frequently perceived to be unstable, and patients may have activity-related pain or swelling, difficulty walking down- *Address correspondence to James H. Lubowitz, MD, Taos 75,93 Orthopaedic Institute Research Foundation, 1219-A Gusdorf Road, Taos, hill or on ice, and trouble coming to a quick stop. NM 87571 (e-mail: [email protected]). Abnormal anterior tibial translation is the basis for clin- No potential conflict of interest declared. ical diagnosis of an ACL-deficient knee using the Lachman and anterior drawer tests and KT-1000 or KT-2000 The American Journal of Sports Medicine, Vol. 36, No. 3 8 DOI: 10.1177/0363546507312641 arthrometer (MEDmetric, San Diego, Calif). Butler et al © 2008 American Orthopaedic Society for Sports Medicine used cadaveric specimens to demonstrate that the ACL is

Downloaded from ajs.sagepub.com at Aarhus Universitets577 Biblioteker / Aarhus University Libraries on December 30, 2010 578 Lubowitz et al The American Journal of Sports Medicine the primary restraint to anterior translation of the tibia, and the ligament’s greatest contribution occurs at 30° of knee flexion. Specifically, the ACL was shown to provide an average restraint of 87.2% to an applied anterior load at 30° flexion and 85.1% at 90°. In addition, Beynnon et al4 established in vivo that the ACL experiences greater strain in response to an anterior load at 30° than at 90°. When the ACL is sectioned, the greatest anterior translation (mean value, 8.4 ± 1.9 mm) occurs at 30°. Secondary sectioning of the medial collateral ligament (MCL) increases anterior translation at 90°, but not at 30°, suggesting that the Lachman test at 30° (described below) carries diagnostic specificity for ACL deficiency.42 In vitro and in vivo analyses thus indicate that the Lachman test is the clinical examination of choice for detec- Figure 1. Lachman test (for anterior instability). With the tion of ACL insufficiency and that the Lachman test places patient supine and the right knee flexed to 30°, an anterior more strain on the ACL than the anterior drawer test (also force is applied to the proximal tibia (arrow). Tibial anterior described). Note that both tests, especially the anterior translation and quality of the endpoint are evaluated. drawer, may be of less value in the acutely injured knee as a result of hemarthrosis and patient pain and guarding. After acute ACL rupture, DeHaven21 found that the Lachman test laxity, 6 mm to 10 mm as grade II, and >10 mm as grade result was positive (increased side-to-side laxity plus soft III. The quality of the endpoint is also graded as firm, soft, endpoint) in only 80% of patients examined without anes- or absent. Here, and below, this grading system and these thesia but in almost 100% of patients examined under anes- qualities are relative to a normal, contralateral knee. thesia. The anterior drawer test finding was positive in only Difficulty performing the test in situations where clini- 10% of patients without anesthesia and 50% of patients cian’s hands are small relative to the patient’s thigh girth under anesthesia. Both tests have a higher diagnostic value can be a limitation of the Lachman test.24-26 In such cases, (approaching 97%) in chronically injured patients.21 a variation on the Lachman test has been described in which the examiner cradles the patient’s leg in the axilla The Lachman Test and places his hands behind the tibia. While pushing the tibia anterior, the examiner attempts to discern excessive Named for his mentor, John W. Lachman, MD, chairman and anterior displacement of the tibia while observing any 71 professor of orthopedic surgery at Temple University, this reduction in the contour of the patella and its tendon. clinical test was originally described by Joseph S. Torg, The sensitivity of this alternative has not been well 79 MD.106 When the test was first discussed, the recommenda- described. The Lachman test is illustrated in Figure 1 tion was for the examiner to hold the knee “between full (all figures illustrate the right knee). extension and 15° of flexion.” Now, however, it is common to place the knee in 30° of flexion. One must ensure that the The Anterior Drawer Test tibia is not subluxated posteriorly to avoid a false-positive test result and misdiagnosis of ACL insufficiency in a poste- The origins of the anterior drawer test are obscure,106 rior cruciate ligament (PCL)–deficient knee. The tibia must although before the introduction of the Lachman test, the rest in neutral rotation because internal or external rotation anterior drawer was the usual clinical examination for will recruit secondary stabilizers, thereby confounding diagnosis of an ACL tear. Despite its historical importance, assessment of the ACL.80 The Lachman test offers high many authors have questioned its reliability and validity sensitivity and high specificity (approaching 95%).62 False- in the diagnosis of ACL injury.106 The posterior meniscal negative results have been attributed to concomitant horns or the bony contour of the joint may interfere with bucket-handle meniscal tears that interfere with anterior the test. Additional limitations of the anterior drawer test tibial translation106 or scarring of a torn ACL to the PCL, are the impracticality of requiring 90° of flexion in an although some data indicate that additional meniscal or lig- acutely injured or swollen knee, hamstring spasm that amentous injuries generally do not alter test sensitivity.23 may restrict anterior translation at 90°, and secondary sta- Recommended Technique. With the patient supine and bilization against anterior translation of the knee at 90° the knee positioned in 30° of flexion, the examiner stabi- flexion by the MCL.101 Whereas test accuracy may improve lizes the anterolateral distal femur with one hand and uses in patients with chronic injury or loss of secondary the other hand to exert firm pressure on the posterior aspect restraints to anterior displacement, sensitivity in an alert of the proximal tibia in an attempt to induce anterior dis- patient is variably reported from 22% to 95%, although it placement. Proprioceptive and/or visible anterior translation is reported to improve to between 50% and 95% in the of the tibia beyond the femur with a “mushy” or “soft” end- anesthetized patient.23,43,59,62,64,67,86,96 point represents a positive test result.106 Qualitative and Recommended Technique. The patient is placed in a quantitative measures describe the results of the test, gener- supine position with the knee flexed to 90° and the tibia in ally in comparison with the contralateral normal knee. neutral rotation. The femoral condyles should normally be Anterior translation of 1 mm to 5 mm is defined as grade I palpable 1 cm posterior relative to the anteromedial tibial

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Figure 2. Anterior drawer test (for anterior instability). With the patient supine and the right knee flexed to 90°, an ante- Figure 3. KT-1000 arthrometer test (for anterior instability). rior force is applied to the proximal tibia (arrow). Tibial ante- With the patient supine and the right knee supported at 30° of rior translation and quality of the endpoint are evaluated. flexion on the thigh support, the patient’s thighs and heels are placed against lateral thigh and foot rests. Arrows on the arthrometer are pointed at the joint line, and pads are secured ® plateau, and this relationship should be confirmed before against the tibial tubercle and patella using Velcro straps. The performing the anterior drawer test to avoid misdiagnosis in 34,79 examiner places the thumb of the hand not used to apply the a PCL-deficient knee. The patient must be encouraged to anterior force on the patellar pad and the remaining fingers of relax the hamstring muscles fully so as to minimize ham- this hand on the patient’s lateral thigh. The arthrometer is first string dynamic resistance to anterior tibial translation. calibrated. Next, an anterior force is applied to the proximal When the patient is sufficiently relaxed, the examiner tibia (arrow), and anterior tibial translation at 15 lb, 20 lb, and grasps the proximal tibia with both hands while placing manual maximum force is determined. both thumbs along the anterior joint line. A positive test result is indicated by increased anterior translation and a soft endpoint and graded similar to the Lachman test. The translation and inferior malposition resulting in a anterior drawer test is illustrated in Figure 2. decreased measurement.68 Before establishing the zero calibration point, the examiner places the thumb of the KT-1000 and KT-2000 Arthrometry hand not used to apply the anterior force on the patellar pad and the remaining fingers of this hand to the patient’s The KT-1000 and KT-2000 arthrometers (MEDmetric) are the lateral thigh. This stabilizes the measurement pad against devices most widely used to quantify anterior tibial transla- the patella, engages the patella in the trochlear grove, and tion. They provide an objective measure of anterior laxity and prevents rotation or changes in position of the patellar pad 20 have been shown to be both accurate and reliable.88 As with in relation to the joint line. the Lachman and particularly the anterior drawer test, Once the arthrometer is secured, alternating anterior patient relaxation, correct positioning, and application of an and posterior forces are applied a few times to the handle anteriorly directed force are required.7,20,22,68 At 30° of knee of the device to adjust the arthrometer to the zero point. flexion and application of 20 lb (89 N) force, a maximum side- After the reference point has been established, anterior to-side difference of >3 mm, a maximum manual translation of translation measurements are recorded as 3 different >10 mm, or a compliance index (difference in translation forces are applied through the arthrometer handle. First, between the 89- and 67-N tests) >2 mm were shown to corre- an anterior force of 15 lb (67 N) is applied, indicated by an late with ACL insufficiency.2 Others have reported that a side- initial audible tone. Second, a force of 20 lb (89 N) is to-side difference of <3 mm is a better indicator of an intact applied, indicated by a different audible tone. Finally a ACL than an absolute measurement.88 manual maximum force is applied to the posterior aspect Recommended Technique. KT arthrometer testing is per- of the proximal tibia, as in the Lachman test. The KT-1000 formed by first positioning the supine patient’s knees in arthrometer test is illustrated in Figure 3. 30° of flexion on the thigh support. With tall patients, it may be necessary to raise the thigh support to reach 30° of The Pivot-Shift Test flexion. The patient’s thighs and heels are then placed against the lateral thigh and foot rests to ensure neutral While the phenomenon was recognized by numerous authors, rotation and standard stance distance. The device is placed the term “pivot shift” was first coined and described by Galway against the knee to be tested (generally the normal knee is and MacIntosh.38 This term is used to both denote a specific tested first), with the arrows of the arthrometer pointing sign that may be elicited during physical examination and to directly at the joint line and the measurement pads characterize a patient’s subjective description of their knee secured against the tibial tubercle and patella using “going out” during an attempt to laterally pivot.71,78,79 The ® Velcro straps. Malposition of the arthrometer by as little pivot shift does not actually represent a knee instability event as 1 cm has been shown to influence results, with proximal itself but rather a reduction from a state of anterior tibial sub- malposition causing an increase in measured anterior luxation.28 Slocum et al103 and Losee et al76 have described

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 580 Lubowitz et al The American Journal of Sports Medicine important variations of the pivot-shift test. In the original A final and often overlooked factor is hip position. It has description of the pivot-shift maneuver, it was revealed been shown that both hip position and tibial rotation inde- that ACL sectioning alone caused the phenomenon in 89% pendently and collectively affect the grade of the pivot of cadaveric knees tested. In contrast, sectioning of the ili- shift. According to Bach et al,1 a combination of hip abduc- otibial band (ITB), biceps tendon, lateral collateral liga- tion and external tibial rotation produces statistically ment (LCL), and popliteus was insufficient to produce a higher pivot-shift grades, whereas hip adduction combined pivot shift.38 The pivot-shift test is particularly useful for with either internal or external tibial rotation lowers the confirming that anterior laxity is likely to be clinically sig- grade. It has been shown that internal rotation of the tibia nificant65 and may thus represent a relative indication for and adduction of the hip both tighten the ITB, causing ear- ACL reconstructive surgery. lier tibial reduction and a consequent decreased grade.20 To perform the pivot-shift maneuver successfully, the The potential effect of hip and tibial positioning on locking examiner must appreciate subtle motions of the knee. As and unlocking of the knee has been proposed as another stated succinctly by Cummings and Pedowitz, “The goal is to explanation for these observations.72 In summary, whether observe a sudden shift of the tibia relative to the femur as the by this mechanism or by the effect on the ITB or some com- knee goes from an extended to a slightly flexed position.”18 bination thereof, abduction and slight flexion of the hip Studies of the pivot-shift test have reported high sensitivities may be used to enhance the positive results of a pivot-shift for detecting ACL injury ranging from 84% to 98.4%. The test.1,56,89 It has been suggested that when performing the test’s specificity has been shown to vary more widely, with pivot-shift test, one should not rely on a “1 test, 1 position” reported values from as low as 35% in the alert patient to as evaluation of the pivot-shift phenomenon.72 high as 98.4% in the anesthetized patient.23,62,77 The examiner should be aware of the possibility of false The pivot-shift phenomenon may be explained as follows. findings from a pivot-shift test.34,46,58,74,96 In the ACL-deficient knee, anterior subluxation occurs in knee extension. When the PCL and posterior capsule are • Ligamentous laxity in the face of an intact ACL may relaxed by initiation of knee flexion, a valgus stress will allow a subluxation to occur that mimics a positive cause persistent anterior subluxation of the lateral tibial pivot-shift test result. Therefore, both knees must plateau due to tibial contact with the lesser curvature of the always be tested. lateral femoral condyle. As the posterolateral tibial plateau • Rupture of the ITB prohibits the telltale reduction phe- shifts anteriorly, it impinges against the lateral femoral nomenon. Losee74 reported that an insufficient ITB condyle at its greater curvature. This impingement prevents will permit continued subluxation through increased further anterolateral tibial subluxation and causes a hinging knee flexion (beyond 40°). effect at the site of impingement. Continued flexion levers • Medial instability can prevent the necessary valgus open the anterior aspect of the knee, generating a critical forces from being applied to elicit a positive pivot tension in the ITB acting at the anterior lateral tibial tuber- shift. cle (Gerdy tubercle). At 30° to 40° of knee flexion, the ITB • A locked bucket-handle tear of the meniscus may changes in relation to the axis of the knee, specifically chang- block a pivot-shift phenomenon from occurring. ing from a knee extensor to a knee flexor. Tension in the ITB • The posterior horn of the lateral meniscus may act as pulls the subluxated lateral tibial plateau posteriorly, the a buttress against anterior subluxation of the antero- tibia no longer impinges on the femoral condyle, and the lateral tibial plateau. Thus, in the absence of an examiner perceives a sudden clunk as the joint reduces. This intact posterior horn lateral meniscus, there may be reduction phenomenon allows the examiner to appreciate a a blunting of the clinical test because the tibia can positive pivot-shift sign.76 slip beneath the femur in a more subtle fashion, Critical maneuvers in the pivot-shift test, in addition to without the expected “sudden jump.” internal tibial rotation and valgus stress mentioned above, may also include ranging the tibia through external rota- Recommended Technique. In this test, the patient tion and positioning of the hip. Some authors have sug- assumes a supine position and attempts to relax the leg gested that external rotation of the tibia can produce an muscles as much as possible. The examiner holds the equal or greater pivot-shift sign on physical examina- affected leg in full extension and internal rotation while lift- tion.1,11,56,89 However, evaluation of the pivot shift using the ing the limb off of the table. The knee is flexed during appli- externally rotated tibia must be distinguished from cation of concomitant valgus stress. In an ACL-deficient demonstrations of posterolateral laxity. Gollehon et al39 knee, the lateral tibial plateau will be anteriorly subluxated showed that the posterolateral structures of the knee at the beginning of the test (knee flexion less than 30° plus resist external tibial rotation but can be differentiated valgus stress). As flexion increases to 30° to 40°, this antero- from the pivot shift in external rotation by 2 methods. lateral tibial subluxation will abruptly reduce (positive test First, the pivot shift will remain positive when tested in result). This is palpable and sometimes audible. internal rotation, whereas the laxity secondary to postero- The grading system for the pivot-shift test is based on lateral damage will not. Second, careful palpation of the the relocation event, specifically the difficulty and abrupt- lateral tibial plateau in relation to the femoral condyle will ness with which the tibia reduces. Grade 0 is considered allow the examiner to differentiate posterolateral versus normal, with no reduction or shift noted. Grade I repre- anteromedial subluxation.39 (This is reiterated in the dis- sents a smooth glide with a slight shift; grade II is when cussion of rotational instability below.) the tibia is felt to “jump” back into a reduced position and

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Multiple cutting studies have shown that isolated sectioning of the PCL results in increased posterior translation of 15 mm to 20 mm, occurring maximally at 90° of knee flexion.16,63 The tensile strength of the PCL is almost twice that of the ACL, and the load-bearing capacity, stiffness, and size of the anterolateral (AL) bundle of the PCL are greater than that of both the posteromedial (PM) PCL bundle and the meniscofemoral ligaments, suggesting that the AL bundle is primarily responsible for the biomechanical properties of the PCL.45,63 Without additional damage Figure 4. Pivot-shift test (for anterior instability). With the to the PLC, isolated sectioning of the PCL has no effect on patient supine and the right knee extended, the ACL-deficient internal or external rotation, nor is there any increase in knee demonstrates anterior tibial subluxation (A). As the varus or valgus opening.16,63 Consequently, the most appro- patient’s knee is flexed to 30° to 40° while valgus force is priate test for evaluating isolated PCL injury is a test that applied, anterolateral tibial subluxation will abruptly reduce (B). assesses posterior tibial translation alone. can be described as a moderate shift; and grade III is when Posterior Drawer Test the tibia is transiently locked anterior to the lateral femoral condyle just before a dramatic reduction with As with the anterior drawer test, the origins of this test are shift. Jakob et al56 elaborated on this grading system in obscure. The posterior drawer test has been reported to be the most sensitive test in the evaluation of isolated PCL terms of its clinical significance. In their description, grade I 12,17,22,97 occurred in internal rotation only and was appreciated as a injury with a double-blind, randomized controlled study documenting 90% sensitivity. This test has also been small and gentle sliding reduction correlating with a trace 98 shift. Grade II is positive in both internal and neutral tibial shown to have 99% specificity for PCL injuries. In addi- rotation, reducing with external rotation, and it is this grade tion, the accuracy of this test is enhanced when its findings are combined with information from other tests of poste- that was considered to be most consistent with isolated rup- 79 ture of the ACL. Grade III is positive in neutral tibial rotation, rior instability. even more pronounced in external rotation, and moderate in The examiner must also be aware of the potential for internal rotation. It is seen in acutely injured knees where false-negative results. both the posteromedial and posterolateral corners are dam- • aged.56 The pivot-shift test is illustrated in Figure 4. If tested in internal rotation, intact meniscotibial ligaments, especially that of Wrisberg, may allow for an improvement of 1 grade. Clancy et al12 reported that POSTERIOR INSTABILITY the meniscofemoral ligaments (MFLs) are rarely injured with an isolated PCL tear and that they can Excessive posterior translation of the tibia on the femur is actually eliminate the posterior drawer as they prevented primarily by the PCL and secondarily by the tighten in internal rotation. 12,15,16,27,39,105 posterolateral corner (PLC), LCL, and MCL. • Hughston48 believed that PCL rupture may be pres- Damage to the PCL may occur by several different mecha- ent when the posterior drawer is positive in internal nisms, including both low-energy and high-energy injuries rotation but that the test finding may be falsely neg- in which a posteriorly directed force is applied to the prox- ative in an acute injury if the mechanism does not imal tibia of a flexed knee. This may happen when an ath- involve the arcuate complex. In such cases, a positive lete falls with the foot in plantar flexion or as a result of a valgus stress test result at 0° (described below) may “dashboard injury” during a motor vehicle accident. then be diagnostic of an acute PCL tear.34 Hyperextension of the knee can also rupture the PCL, and this scenario is associated with a high likelihood of knee Recommended Technique. Before dynamic evaluation of dislocation and injury to other ligaments.12,18,30,31,33,57 the affected knee, it is important to establish the normal Symptoms of PCL deficiency include pain, stiffness, and relationship between the medial tibial plateau and the swelling in the knee. Instability is occasionally noted but medial femoral condyle with the knee flexed to 90°. with less frequency than in ACL deficiency.18 Although Pathologic posterior translation will be graded with this PCL injuries may occur in isolation, they are usually part relationship in mind. As mentioned, the tibial plateau of a complex injury, with PLC involvement occurring in should normally be 1 cm anterior to the medial femoral 60% or more cases of PCL tears.30 Clinical tests that reveal condyle. Comparison with the contralateral, uninjured excessive posterior tibial translation include the posterior knee provides an additional measure of “normal.” The drawer, posterior Lachman, and posterior sag tests. The patient is placed supine with the affected knee flexed to quadriceps active test demonstrates pathologic, dynamic 90° and the tibia in neutral rotation. The examiner then anterior tibial translation in the setting of a PCL tear with places both hands along the anterior aspect of the proxi- sag. Some research indicates that in patients with chronic mal tibia with the thumbs lying on the anterior joint line PCL injury, the sensitivity of these clinical tests increases of both the medial and lateral compartments. A posteriorly when the ligament sprain is at least grade II.98 directed force is applied equally with both hands and

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 582 Lubowitz et al The American Journal of Sports Medicine graded based on the amount of pathologic posterior tibial translation that occurs. Hughston et al51 suggested that a negative posterior drawer test finding with the tibia in neutral or internal rotation can help to rule out PCL injury and that performing the posterior drawer test with and without internal tibial rotation can be useful in distin- guishing a positive result for posterolateral rotatory subluxation from a positive result for a PCL tear, as rotatory instability may sometimes be appreciated in the internally rotated knee.51 As with many other tests, grade I PCL laxity is consistent with translation of 0 to 5 mm (and the tibial plateau remains anterior to the femoral condyle). Grade II is clas- sified by posterior translation of 6 mm to 10 mm (which correlates with the tibial plateau being flush with the Figure 5. Posterior drawer test (for posterior instability). With femoral condyle). Grade III injuries measure >10 mm of the patient supine and the right knee flexed to 90°, a normal posterior translation (and allow the tibial plateau to trans- anatomical relationship between the tibia and femur is estab- late posterior to the femoral condyle). The quality of the lished. Next, a posterior force is applied to the proximal tibia endpoint is also graded as “firm, soft, or absent.” (arrow). Tibial posterior translation and quality of the Shelbourne et al100 pointed out that the endpoint may endpoint are evaluated. return to firm within the first 2 weeks after a PCL tear as a result of intact supporting structures. In these circumstances, or when evaluating chronic injuries, translation can be considered more reliable than the endpoint in the assessment of PCL status. The posterior drawer test is illustrated in Figure 5.

The Posterior Lachman Test

Although the PCL has been shown to provide all of the resistance to posterior tibial translation when the knee is Figure 6. Posterior sag test (for posterior instability). Patient flexed to 90°, the posterior drawer test can be difficult to lays supine with the knees flexed to 90° and the feet flat on perform in the acutely injured knee because of patient dis- examination table. The patient relaxes, and in comparison comfort during knee flexion.34,107 In such situations, the with the normal anatomical relationship between the tibia posterior Lachman test may be useful in diagnosing sus- and femur (A), the PCL-deficient knee demonstrates a pos- pected PCL injury because the knee is only required to flex terior sag of the tibial tubercle relative to the femur (B). to 30°. At this angle, the PCL is still responsible for pro- viding 85% of the resistance to posterior translation.34 Recommended Technique. With the patient’s knee flexed to 30°, the examiner should place his or her hands as in the posterior drawer test so that any variation in the normal Recommended Technique. The patient is placed supine relationship of the tibia and the femur can be appreciated; with knees flexed to 90°. The patient’s feet are allowed to in the PCL-deficient knee, the tibia must be anatomically rest flat on the examination table, and the patient is reduced at the start of this test. A posteriorly directed force encouraged to relax completely, especially relaxing their is then exerted on the tibia. It is again important to main- quadriceps. The affected knee is then viewed from the side. tain neutral rotation to avoid recruitment of secondary sta- A positive result is when the anterior aspect of the proxi- bilizers. Grading is consistent with the systems used mal tibia is found to “sag” posterior to the anterior aspect above. One caveat for the examiner is that a slight increase of the femoral condyles or in comparison with the normal, 3,61 in posterior translation with the knee at 30° but not at 90° contralateral knee. The posterior sag test is illustrated may indicate a PLC injury, whereas increased translation in Figure 6. at both positions, with maximal translation at 90°, is con- 22 sistent with PCL injury. The Quadriceps Active Test

The Posterior Sag Test As opposed to passive tests, which rely on externally imposed forces, this test uses the patient’s own quadriceps contraction As opposed to the posterior drawer, which is a dynamic as the displacement force. The test was originally described clinical test, the posterior sag test is a static test. It has by Daniel et al20 who reported identifying confirmed PCL dis- been shown to have 100% specificity for detecting PCL ruption in 41 of 42 knees, while pathologic anterior tibial injuries. Its sensitivity has been reported at 79% by translation did not occur in any patient’s contralateral, nor- Rubenstein et al.98 mal knee, nor in 25 other normal knees, nor in knees with

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 Vol. 36, No. 3, 2008 Knee Physical Exam 583 documented ACL disruption. It should be noted that previ- ous injury or surgery altering the native orientation of the patellar ligament may render the quadriceps active test use- less.20 Although it is reported to be highly sensitive and specific in the original description of the test, the quadriceps active test was found by other researchers to be less sensitive (54%) compared with other tests for PCL deficiency.98 A second use of this maneuver is to determine the quadriceps neutral angle of the patient’s normal, contralateral knee—that is, the angle at which a quadriceps contraction produces no apparent tibial shift (usually around 60° to 70° of flexion). At the quadriceps neutral angle, the vector of force generated by the quadriceps is parallel to the tibial shaft, and contraction of the quadriceps at this angle will merely increase joint contact pressure if the foot is prevented from moving. By locating the quadriceps neutral Figure 7. Quadriceps active test (for posterior instability). angle in the patient’s normal knee, deviations from normal With the patient supine and the right knee flexed to 90°, the may be better understood in the injured knee for detection patient is asked to attempt to slide his or her fixed foot ante- of both anterior and posterior laxity. riorly, inducing a quadriceps contraction (right arrow). The Recommended Technique. The patient is placed in the posteriorly subluxated tibia is observed to reduce (left arrow). supine position with the knee flexed to 90°. The flexion angle of the knee at which the test is performed is critical and must exceed the quadriceps neutral angle described (POL), the semimembranosus expansions, the meniscotibial above. At 90° flexion, the quadriceps force vector angle (coronary) ligaments, and the oblique popliteal ligament.102 includes a component of anterior drawer in relation to the Anteromedial rotatory instability typically results from an shaft of the tibia. Thus, if a patient is asked to attempt to abrupt external rotation-abduction force, such as occurs dur- slide their fixed foot anteriorly (inducing a gentle quadri- ing a “clipping” injury in American football. Anteromedial ceps contraction), a sagged or posteriorly subluxated tibia rotatory instability may represent the most common form of will move in an anterior direction. This dynamic reduction knee instability in addition to the most frequent cause of ACL of the tibia in relation to the femur represents a positive disruption; however, disability associated with AMRI may, at result for PCL deficiency if the tibia shifts anteriorly by at first, be minimal. Over time, this type of instability often pro- least 2 mm.20 The quadriceps active test is illustrated in gresses to associated anterolateral rotatory instability Figure 7. (ALRI), and when AMRI is combined with ALRI, the functional disability may be significantly more incapacitating.28 ROTATORY INSTABILITIES The Slocum Test Rotatory instabilities primarily affect knee function in flexion. Gait analysis indicates that during normal walk- The Slocum test104 is based on the premise that the PMC ing, the knee flexes between 0° and 20°, whereas during is a secondary stabilizer against anterior translation in the running, knee flexion increases in direct proportion to rate. flexed ACL-deficient knee when the tibia is externally In full extension and maximum weightbearing, no rotation rotated. Thus a positive test result is represented by fail- is present (neutral rotation). External rotation of the tibia ure of tibial external rotation to diminish the anterior relative to the femur commences with knee flexion, with drawer in an ACL-deficient knee. A differential diagnosis maximum rotation occurring between 60° and 90° of flex- for AMRI is posterolateral rotatory instability (PLRI) and 71 ion. Isolated rotatory instabilities may manifest during vice versa. Posterolateral rotatory instability is diagnosed cutting, pivoting, or rapid deceleration activity in a man- using the dial test (described in detail below). When a diag- ner similar to combined ligamentous instability, and mul- nosis of AMRI or PLRI is suggested based on the Slocum or 71 tiple directions of rotatory instability may also present. dial test results, respectively, the examiner must carefully determine whether the anteromedial tibia is rotating ante- Anteromedial Rotatory Instability (AMRI) riorly relative to the medial femoral condyle (AMRI) versus whether the posterolateral tibia lateral is rotating Slocum et al104 described excessive valgus motion coupled posteriorly relative to the lateral femoral condyle (PLRI). with external rotation of the knee as AMRI. This occurs This is reviewed in the discussion of PLRI. when the anteromedial tibial plateau subluxates anterior to Recommended Technique. To evaluate the knee for AMRI, the corresponding femoral condyle. The posteromedial corner the anterior drawer test is performed as described above. (PMC) has been shown to serve as a restraint to AMRI Increased anterior translation of the tibia relative to the throughout the normal range of motion. The PMC is func- femur will be noted in an ACL-deficient knee. Next, the test tionally composed of 5 anatomic structures: the posterior is repeated with the foot fixed in approximately 15° of exter- horn of the medial meniscus, the posterior oblique ligament nal rotation, tightening the PMC, and secondarily reducing

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 584 Lubowitz et al The American Journal of Sports Medicine the positive anterior drawer. Absence of this reduction of become equally prominent during the anterior drawer test anterior translation during external rotation as a result of with the tibia in neutral rotation, this is suggestive of PMC deficiency is a positive test finding for AMRI. As ALRI and should be followed by a confirmatory jerk test as some degree of physiologic anteromedial rotation is to be described below. expected and the normal tissue laxity may vary, compari- 71 son with the uninjured contralateral knee is required. Accessory Tests for ALRI

Anterolateral Rotatory Instability (ALRI) In addition to the pivot-shift and anterior drawer tests, the following clinical tests may confirm ALRI. An important secondary function of the ACL is the pre- vention of rotational instability of the knee joint by pre- The Jerk Test of Hughston vention of excessive internal rotation of the tibia relative to the femur. Several clinical tests, including the pivot-shift This maneuver is a variation on the pivot-shift test and test, the anterior drawer test with the tibia in neutral rota- may be considered its opposite. It has been described as the tion, and various accessory tests, may be used to assess the most specific test for ALRI by its eponymous author.51 presence and degree of ALRI. If all test results are nega- Recommended Technique. The patient is placed supine tive, yet ALRI is still suspected, examination under anes- with the affected knee in 90° of flexion and the tibia in mod- thesia (EUA) may be of value. Anterior cruciate ligament erate internal rotation. Valgus stress is applied to the knee, injuries associated with ALRI are not uncommon. Norwood and the joint is slowly extended. In a positive test result, the and Cross90 reported that EUA reveals unsuspected ALRI tibia will be maximally displaced anteriorly and internally at in 18% of patients treated operatively for ACL deficiency. approximately 30°, and the examiner will feel a sudden Anterolateral rotatory instability typically results when “jerk.” Continued extension of the limb will somewhat reduce there is acute internal rotation and varus stress on the the anterolateral tibial subluxation, although anterior sub- weightbearing knee, such as when a basketball player loses luxation will persist in the ACL-deficient knee. his balance while landing from a jump.51 According to A torn meniscus may generate a false-positive finding if the Hughston et al,51 injury to the middle one third of the lateral meniscus distracts the femorotibial joint through its interpo- capsular ligament is implicated in this type of instability sition between the joint surfaces.51 Alternatively, the jerk that and may underlie ALRI in cases when the ACL is intact. occurs during subluxation of the lateral tibial plateau and is Symptoms include a perception of instability as the knee sometimes associated with medial joint pain may be misin- approaches extension, and in cases of coexisting meniscal terpreted as a medial meniscal tear with an ensuing inappro- injuries, ALRI must be ruled out before a patient’s symp- priate intervention. Some critics believe that the jerk test toms should be ascribed to the meniscal tear alone. may produce a substantial number of false-positive results76 Hsieh and Walker47 showed that at 30° of flexion, the because when a patient’s foot is internally rotated at the start axis of internal rotation in the transverse plane is located of the test, there may be physiological anterolateral tibia sub- on the medial side of the knee. Therefore, the secondary luxation. Next, when subsequent application of valgus stress structures anatomically most effective at reducing ALRI compresses the lateral compartment, this compression may (internal rotational laxity in the presence of lateral capsu- cause a sense of reduction obvious to the examiner and the lar injury) are the ACL and the MCL. The PCL is substan- patient even when ALRI does not exist. The jerk test is illus- tially less able to resist anterolateral rotation than the trated in Figure 8. ACL because its insertion is in close proximity to the transverse axis of rotation and because it is more vertically The Losee Test oriented than the ACL.47 Fleming et al32 found that the application of an internal rotation force to the tibia pro- This test was originally described in 1978 by Losee et al duces an increase in ACL strain, and the additional appli- (who believed that this eponymous maneuver was more cation of valgus stress plus internal rotation increases reliable than the jerk test).76 Dr Ronald Losee shared ACL strain values significantly compared with internal Hughston’s concern that beginning tests for ALRI with the rotation in isolation. The highest ACL strain values are knee in extension creates impingement between the lat- found at knee flexion angles of 0° to 30°,32 whereas at flex- eral femoral condyle and the posterolateral tibia plateau, ion angles of greater than 30°, ACL strain decreases with inducing pain, guarding, hamstring spasm, and damage to the recruitment of secondary stabilizers.60,112 These find- the lateral femoral condyle. ings are consistent with the observation that clinically sig- Recommended Technique. The Losee test begins with the nificant anterolateral tibial subluxation in the context of knee held at 45° of flexion and the tibia in external rotation. ACL incompetence occurs at flexion angles from 0° to 30°. This ensures that the knee begins in a reduced position. As above, detection of anterior tibial translation in com- External rotation also accentuates the clunk, which repre- bination with tibial internal rotation by use of the pivot- sents a positive test result. The knee is slowly extended shift test, the anterior drawer test in neutral rotation, and while valgus force is applied. The valgus stress is a key com- accessory tests serves as a basis for identifying ALRI. The ponent of this maneuver because it applies a compressive pivot-shift and anterior drawer tests have been described load to the lateral compartment, which also accentuates a above. According to Hughston et al,51 when the lateral tib- clunking subluxation episode. The leg and foot are allowed ial condyle becomes more prominent or both condyles to drift into internal rotation. In a positive test finding,

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Figure 8. The jerk test of Hughston (for anterolateral rotatory instability). With the patient supine, the right knee is sup- Figure 10. Side-lying test of Slocum (for anterolateral rota- ported at 30° with mild tibial internal rotation (A). As the tory instability). With the patient in the lateral decubitus posi- patient’s knee is extended while valgus force is applied, a tion with effected knee superior and fully extended while the sudden anterior “jerk” of the tibia with increased internal effected foot rests on the examination table with the ipsilat- rotation occurs at approximately 30° as the tibia subluxates eral pelvis in 30° of external rotation, the involved knee is with knee extension (B). allowed to sag into varus and internal rotation (A). The examiner flexes the patient’s knee while applying an anterior drawer (B). The anteriorly subluxated anterolateral tibia is noted to reduce (small arrows) at 25° to 45°.

bony architecture of the knee. Anterior subluxation of the lateral tibia may be appreciated at the joint line. The examiner then places both hands on the leg with the thumbs posterior and the fingers anterior and applies an anterior Figure 9. The Losee test (for anterolateral rotatory instability). drawer while flexing the knee. A positive test result consists With the patient supine, the right knee is supported at 45° of audible and/or palpable reduction occurring as the knee is with tibial external rotation (left arrow). As the patient’s knee flexed and as the ITB changes from a knee extensor to a is extended while valgus force is applied, the leg and foot are knee flexor between 25° and 45°. The side-lying test of allowed to drift into internal rotation (right arrow), and at Slocum is illustrated in Figure 10. approximately 20°, the lateral tibia subluxates anteriorly with a “clunk.” The Flexion Rotation Drawer Test when the knee reaches approximately 20° of flexion, the This test was originally described by Noyes et al,91 who lateral tibial plateau shifts anteriorly, which will be per- suggested that it had the potential to detect ALRI in cases ceived by the examiner and should also be recognized by where a pivot-shift phenomenon has yet to develop. This the patient as a typical episode of joint instability.71,75 The test may also be easier to perform than other tibial trans- Losee test is illustrated in Figure 9. lation tests. The flexion rotation drawer test builds on the Lachman test in that femoral rotation as well as tibial The Side-Lying Test of Slocum translation are observed. Recommended Technique. The patient relaxes in the Slocum was the first to suggest the term ALRI and devel- supine position, with the examiner holding the affected oped a version of the pivot-shift test as a means of ascer- tibia in neutral rotation at 15° of knee flexion using one taining this disorder.103 The side-lying test of Slocum may hand. In the ACL-deficient knee, the femur drops posteri- be especially useful in the acute setting and whenever a orly and rotates externally. As the examiner flexes the patient has hamstring spasm or guarding or when a knee using his other hand, reduction of the tibia with an patient’s leg is too heavy to easily manipulate. internal rotation of the femur is appreciated as the knee Recommended Technique. The patient is placed in the lat- approaches 40° flexion. Ranging the knee through gentle eral decubitus position with the effected side up, the pelvis in flexion and extension enables the examiner to note sub- 30° of ipsilateral external rotation, and the knee in question luxation and rotation. The flexion rotation drawer test is fully extended. The medial aspect of the affected foot is illustrated in Figure 11. placed on the examination table, permitting the affected knee to sag into varus. With the knee in this position, the Posteromedial Rotatory Instability (PMRI) tibia rotates internally, tension is applied to the MCL and medial capsule, and the lateral tibial plateau and lateral This is a least common form of rotatory instability, pro- femoral condyle are compressed. This position minimizes duced by concomitant valgus force and hyperextension of the restricting effects of muscle tension, yet some authors the knee, which lead to injury of the medial capsular liga- recommend slight knee flexion (approximately 10°) so as to ment, tibial collateral ligament, POL, and ACL. When remove other stabilizing influences, such as that provided these structures are damaged, the proximal medial tibia by tension of the PCL and posterior capsule as well as the sags posteriorly. This sag will only occur in the context of

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sectioned in different sequences to establish their importance and contribution to static knee stability. Anteroposterior translation, internal and external rotation, as well as varus and valgus motions were evaluated after sectioning of the various structures. Isolated sectioning of the PLC resulted in an increase in posterior translation (especially as the knee approached full extension), Figure 11. Flexion rotation drawer test (for anterolateral rota- an increase in external tibial rotation, and an increase in tory instability). With the patient supine, the tibia is supported varus instability (with the greatest increase in varus noted ° in 15° of knee flexion (A) by the examiner using one hand at 30 ). Combined section of the PLC and the PCL resulted (second arrow from left), and the femur is allowed to sublux- in further increases in external rotation and varus insta- ° ate posteriorly and rotate externally (left arrow). As the exam- bility at 90 . By understanding these aspects of knee iner flexes the knee using the other hand, reduction of the anatomy and biomechanics, such alterations can be tested anteriorly subluxated tibia and internal rotation of the femur clinically using corresponding physical examination tests. is noted at approximately 40° of flexion (B). Posterior translation may be assessed using tests described above. Tests for PLRI are mentioned in this paragraph and described below. Care must be taken to dif- an intact PCL, which supplies a rotational axis for pathologic ferentiate between PLC, PCL, and combined injuries posteromedial shift. If the PCL is torn, the entire tibia will be because both the PLC and PCL may contribute to posterior displaced posteriorly. Posteromedial rotatory instability may tibial restraint depending on the degree of knee flexion. be discerned clinically when the medial tibial plateau shifts Negative posterior drawer testing results with the tibia in posteromedially when valgus stress is applied.71 neutral and internal rotation can assist in ruling out PCL injury.51 Abnormal external tibial rotation can be evalu- Posterolateral Rotatory Instability (PLRI) ated with the dial test and the reverse pivot-shift test. Jakob et al55 have also used the reverse pivot-shift test to The PLC provides restraint to various types of pathologic distinguish PLRI from ALRI. External rotation coupled knee motion: posterior tibial translation near full extension, with posterior translation is assessed with a posteriorly external rotation of the tibia on the femur (where the PCL directed force using the posterolateral drawer test. 52 provides secondary restraint), and varus rotation all are Hughston and Norwood described confirmation of PLRI affected by the structures of the PLC. The PLC is composed with the posterolateral drawer test and the external rota- of both static and dynamic components. The static struc- tion recurvatum test. The posterolateral external rotation tures are the LCL, the arcuate ligament complex (deficien- test may also detect posterolateral subluxation of the lat- cies of which are particularly implicated in PLRI),51,71 the eral tibial plateau: positive findings may also be consistent fabellofibular ligament, and the posterolateral capsule. The with an isolated PLC injury or combined injury to the PLC dynamic structures consist of the ITB, the biceps tendon, and the PCL, depending on the knee angle(s) at which sub- and the popliteus muscle-tendon complex, which includes luxation occurs. These tests are clarified below. Finally, the popliteofibular ligament and its fascicles.44 pathologic varus motion may be detected using the varus Performing a reliable clinical examination of the PLC is stress test at 0° and 30°, which is described below. an important but often underdeveloped skill. Failure to diagnose and treat PLC injury may be a major cause of Dial Test at 30° and 90° 94 failure of ACL reconstructive surgery. Without a thor- (Prone External Rotation Test) ough and competent examination, PLRI may be entirely overlooked as a cause of posterolateral joint pain, or symp- Originally described by Cooper et al15 in 1991, this test toms may be mistakenly attributed to lateral meniscus assesses abnormal external tibial rotation and also helps tear. Chronic PLRI is also frequently misdiagnosed as a differentiate between isolated PLC injury and combination primary tibia vara deformity, with subsequent incorrect PLC/PCL injury. treatment by proximal tibial osteotomy. Posterolateral Recommended Technique. Although this test can be per- rotatory instability generally occurs as a consequence of a formed with the patient prone, supine, or sitting, the force directed posteriorly against the knee with resulting authors15 recommend the prone position. The patient’s knees hyperextension, such as may occur during a block in are initially flexed to 30°. The examiner places both hands on American football.51 Symptoms include posterolateral the feet of the patient, cupping the heels and placing the fin- pain, discomfort with standing, a perception of the knee gers and thumb along either side of the talar-calcaneal bony hyperextending, and the sensation of the knee “giving out.” contours. A maximal external rotation force is applied by the Multiple studies have been performed to establish the examiner, and the foot-thigh angle is measured and compared relative importance of the posterolateral structures.39,41,81 with the contralateral side. The knees are then flexed to 90°, Gollehon et al39 performed selective cutting studies in and again an external rotation force is applied and the foot- fresh cadaveric specimens to establish the roles of the thigh angle is measured. During application of the external PCL, LCL, and the deep ligament complex, consisting of rotation force, it may be useful to palpate the tibial condyles the popliteus tendon, arcuate ligament, fabellofibular liga- to determine their position in relation to the femoral condyles ment, and posterolateral capsule. These structures were before measuring the foot-thigh angle. When comparing the

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Figure 13. Reverse pivot shift (for posterolateral rotatory instability and in anterolateral rotatory instability). With the patient supine and the right knee flexed to 90° and the tibia Figure 12. Dial test (for posterolateral rotatory instability). externally rotated, the PLC-deficient knee exhibits postero- With the patient prone or supine (illustrated), an external lateral tibial subluxation (A). As the patient’s knee is extended rotation force is applied with knees flexed to 30° and then while valgus force and axial load are applied, posterolateral flexed to 90° (illustrated). Side-to-side foot-thigh angle differ- tibial subluxation will palpably shift at approximately 30° as ence of greater than 10° of external rotation is considered the tibia reduces with knee extension (B). positive (right knee illustrated as positive). ITB changes from a flexion vector to an extension vector, degree of limb external rotation, a difference of 10° or more thereby reducing the rotatory subluxation through its pull is significant. on the Gerdy tubercle.55 Posterolateral subluxation of the lateral tibial plateau The examiner should be alert to the potential for false- indicates PLRI; anteromedial subluxation of the medial positive results. Generalized ligamentous laxity and mild tibial plateau is consistent with AMRI as noted in the sec- varus alignment have been shown to yield positive test results tion describing AMRI above. Once PLRI is confirmed and in normal subjects. Furthermore, the test findings may be pos- foot-thigh measurements have been taken, results of the itive in up to 30% of normal knees, especially under anesthe- test are interpreted. An isolated PLC injury is diagnosed if sia. A positive test finding is only considered to be clinically there is greater than 10° of external rotation versus the significant when there is a history of trauma, when the reduc- contralateral side at 30° of flexion but not at 90°. An impor- tion phenomenon reproduces the patient’s symptoms, and tant point is that, in this scenario, the external rotation of when the finding is present only in the affected knee.15 The the involved knee actually diminishes when it is flexed to reverse pivot-shift test is illustrated in Figure 13. 90° because of restraint in the context of an intact PCL. In ° contrast, greater than 10 of increased external rotation in Posterolateral Drawer Test the affected knee at both 30° and 90° suggests a combina- 14,15,39,41,73,108-110 tion PLC and PCL injury. The dial test is This test was originally described by Hughston and illustrated in Figure 12. Norwood in 1980.52 Recommended Technique. The posterolateral drawer test Reverse Pivot-Shift Test essentially comprises the first stage of the reverse pivot- shift test. The patient is positioned supine with the hip The patient’s perception of the knee suddenly “giving out” flexed to 45° and the knee flexed to 90°, with the tibia may occur in the case of PLRI and in ALRI as the tibia shifts placed in 15° of external rotation. The foot position is then posteriorly on the femur. This is the “reverse pivot shift.”55 fixed, and a posterior drawer test (described above) is per- Recommended Technique. The patient is placed in the formed with the examiner’s hands placed along the antero- supine position with the knee flexed to 90° and the tibia in medial and anterolateral joint line. maximal external rotation. The examiner places a hand on In its original description, a positive test result consisted the proximal lateral tibia, applying valgus stress while of palpation of the lateral tibial plateau externally rotating maintaining external tibial rotation. An axial load is also in relation to the lateral femoral condyle; this finding was applied. The examiner’s other hand is placed just distal to believed to be consistent with PLC injury. However, a the first on the anteromedial tibia at midshaft so as to gain grossly positive finding of increased external rotation that full control of the distal leg. The examiner then begins to ensues with posterior tibial force application is more likely extend the knee while maintaining external rotation, axial indicative of a combined PLC and PCL injury, as has been load, and valgus force on the tibia. substantiated by biomechanical evaluation.39,50 In a patient with PLRI, the lateral tibial plateau will be False-negative findings may occur. In a combined PLC posteriorly subluxated at the onset of the test. As the knee and PCL injury, the posterolateral drawer sign will be sub- is passively extended by the examiner, the lateral tibial tler and difficult to appreciate.71 In contrast, when the PLC plateau will reduce with a palpable shift or jerk when the is deficient and the PCL is intact, the medial compartment knee is extended to about 30°. This occurs as the pull of the becomes the new center of joint rotation causing external

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Figure 14. Posterolateral drawer (for posterolateral rotatory instability). With the patient supine and the right knee flexed to 90° (A), a posterior drawer is performed as mentioned above; a positive test result is when the lateral tibial plateau rotates externally relative to the lateral femoral condyle (B). rotation during the test.39 The posterolateral drawer is illustrated in Figure 14.

External Rotation Recurvatum Test Figure 15. External rotation recurvatum (for posterolateral Originally described by Hughston et al50,52 as the ultimate rotatory instability). With the patient supine and the knees diagnostic test for PLRI, the external rotation recurvatum extended, both legs are lifted off the examination table by the test has also been noted to be difficult to interpret. Thus, other great toes. A positive test finding is when the knee falls into tests, such as the posterior and posterolateral drawer tests, varus, hyperextension, and external rotation (arrow and right should be performed to obtain additional diagnostic evidence. knee illustrated as positive). Recommended Technique. Traditionally, the patient is placed supine on the examination table with his or her legs tibial plateau is noted. Subluxation that occurs only at 30° together. With the patient’s knees in extension, the great is consistent with an isolated PLC, whereas subluxation at toes of both feet are then grasped to lift the legs off the both 30° and 90° is indicative of combined injury to the table. A positive result is when the knee falls into varus, PLC and the PCL.10,69 The posterolateral external rotation hyperextension, and external rotation when compared test is illustrated in Figure 16. with the uninvolved side. This finding was originally thought to indicate injury to the PLC; however, excessive varus and hyperextension during the test may indicate VARUS INSTABILITY combined PLC plus ACL or PCL injury.109 A variation on the external rotation recurvatum test The LCL is the major restraint to varus instability at all requires the examiner to hold the heel of the affected limb flexion angles and is secondarily supported by the PLC. while extending the knee from 30° of flexion to full exten- Injury to the LCL results from excessive varus stress and sion. The examiner’s other hand grasps the posterolateral rarely occurs in isolation. Rather, injury to other ligaments aspect of the knee to assess relative hyperextension and usually accompanies an LCL tear. Symptoms vary, depend- external rotation compared with the uninvolved side. ing on the involvement of the PLC and the severity of the 110 According to Veltri and Warren, this test result may be injury. Pain on weightbearing or lateral movement and/or mildly positive in the varus knee with isolated PLC injury; the perception of knee instability during the stance phase again, when there is substantial varus and hyperexten- of gait may be manifestations of varus instability.18 sion, ACL or PCL injury is also likely.The external rotation Only small increases in varus rotation are seen with iso- recurvatum test is illustrated in Figure 15. lated LCL sectioning, with the greatest increase occurring at 30°. This amount, however, may be too subtle to be 110 Posterolateral External Rotation Test appreciated on clinical examination. When the LCL and the lateral deep ligament complex are sectioned together, This is a combination of the posterolateral drawer and dial there is a significant increase in varus rotation at all flex- tests, performed at both 30° and 90°. ion angles, again with the maximum occurring at 30°.A Recommended Technique. With the patient supine, cou- large degree of varus instability at full extension may indi- pled posterior and external rotation forces are applied to cate a combination injury of LCL injury plus the PLC, the tibia of the involved leg in flexion of 30° and then 90°. ACL, or PCL insufficiency.39,108-110 Isolated cruciate injuries The amount of posterolateral subluxation by the lateral have been shown not to affect varus or valgus stability.70

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Figure 17. Varus stress test (for varus instability). With the patient Figure 16. Posterolateral external rotation test (for postero- supine and the right knee at 0° and then flexed to 30°, the exam- lateral rotatory instability). With the patient supine and the iner applies varus force across the joint line (arrows). Lateral joint right knee flexed to 30° and then flexed to 90°, the examiner line opening and quality of the endpoint are evaluated. applies posterior and external rotation forces to the tibia. Posterolateral subluxation of the lateral tibial plateau repre- allows minimal increased opening with varus stress, but the sents a positive test result (arrow). patient may experience pain with the test, usually at the site of the tear in the collateral ligament. Some opening of the Varus Stress Test at 0° and 30° joint line, with a distinct endpoint, yields a grade II score, whereas a grade III tear has no distinct endpoint to applied The origins of using the varus stress test to detect LCL laxity stress, and the knee opens to an almost unlimited degree. are unclear. “Abduction and adduction rocking” of the knee as Hughston’s grading system scores a normal knee as grade 0, a means of examining collateral ligament integrity appears to an increase in joint opening of 1 mm to 4 mm as grade I, an be the antecedent of the current test.96 The varus stress test increase of 5 mm to 9 mm as grade II, and an increase in 10 has undergone little assessment of sensitivity and specificity, mm to 15 mm as grade III. Point tenderness has been shown although a small study suggested that in an emergency room to identify the location of the tear in 78% of cases and local- setting, there may be fairly poor correlation between clinical ized edema in 67%. The O’Donohue grading system contextu- examination and arthroscopic findings.43 alizes positive test results using the degree of sprain assumed Recommended Technique. The patient is placed in the to be present. A mild sprain consists of few torn fibers with no supine position with the tibia held in gentle internal rota- loss of ligament integrity. A moderate sprain corresponds to tion. The examiner places one hand on the medial aspect of incomplete tears with no pathologic laxity, and severe sprains the thigh and the other on the proximal tibia. The involved have loss of integrity with a mushy or indefinite endpoint. knee is flexed to 30°, and a varus force is applied across the Certain anatomic correlates have been established with joint line. The test is then repeated at full extension.69 regard to positive test findings. When there is pathologic The test finding is positive when the lateral joint line can lateral joint line opening at both 0° and 30°, with the maxi- be opened to a greater degree than the uninvolved side. The mum at 30°, this indicates an injury to the LCL and the conventional grading system is based on the amount of lat- PCL, particularly the arcuate ligament. A combination eral joint line opening compared with the contralateral joint. injury to the LCL and PLC, the PCL, and perhaps also the Grade I correlates with a lateral opening of 0 to 5 mm greater ACL is suspected when there is significant lateral opening than the contralateral side, grade II is represented by an at 0°.10,69,110 The varus stress test is illustrated in Figure 17. increased opening of 6 mm to 10 mm, and grade III is an opening of >10 mm versus the uninvolved side. Other grading systems have since evolved, including those VALGUS INSTABILITY of Tria, Hughston, and O’Donohue.13 Tria believes that during testing, the examiner should record both the amount of Biomechanical research indicates that in addition to the opening in millimeters and the quality of the endpoint. In the role of the MCL as a rotational restraint, the anterior Tria grading system, grade I corresponds to a stress test that fibers of the superficial MCL act as the primary restraint

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to valgus load.18,111 In at least 1 study, no significant increase in valgus rotation occurred unless the anterior fibers of the superficial MCL fibers were sectioned. Sectioning of the deep MCL and POL resulted in minimal valgus rotation until the superficial fibers of the MCL were completely cut, at which point 7 mm of medial joint line opening occurred along with up to a 300% increase in valgus rotation.111 In a valgus-restricted model, Grood et al40 showed that the superficial MCL was the primary restraint to valgus stress, responsible for 78% of medial stability at 25° of flexion and 57% at 5° of flexion. Secondary supports against excessive valgus motion are the deep MCL and the POL. Research has shown the POL and the PMC to resist valgus force at 5° of flexion.18 The ACL has also been shown to withstand valgus stress under certain circumstances, such as when the knee approaches full extension in the case of superficial MCL deficiency. In the 5 degrees of freedom model, after the MCL and ACL are sectioned, there are large increases in valgus laxity,54 whereas if freedom of knee motion is not restricted, an applied valgus moment is not resisted solely by the MCL but is in fact shared by other ligaments and joint structures, particularly the ACL, and the ACL is recruited to provide restraint against pathologic valgus instability Figure 18. Valgus stress test (for valgus instability). With the with as little as 5° of abnormal valgus rotation.54 patient supine and the right knee at 0° and then flexed to 30°, the examiner applies valgus force across the joint line Valgus Stress Test at 0° and 30° (arrows). Medial joint line opening and quality of the endpoint are evaluated. Although the accuracy of valgus stress testing is not well defined, the gold standard for evaluating the MCL is the of flexion with relative stability at 0° signifies an isolated valgus stress test performed at 30° of knee flexion with the superficial MCL injury, with the severity of injury based on tibia in external rotation. The valgus stress test in full 50 grade. According to Hughston et al, a valgus stress test extension evaluates the PMC and the POL as well as the positive in full extension denotes injury to both the MCL MCL. The ACL is also an important secondary stabilizer at and the PCL. In their study, ACL integrity was not seen to full extension, but only after the superficial MCL has been affect the valgus stress test in extension. Marshall and compromised. Because most patients with collateral liga- 82 Rubin, however, suggested that in addition to revealing ment injury are treated without surgery, extensive correla- incompetence of the PCM and MCL, a positive test result in tion of clinical examination findings with arthroscopic data extension indicates laxity of either cruciate ligament or has not been performed. One study documented a valgus both. The valgus stress test is illustrated in Figure 18. stress test sensitivity of 86% in 72 patients with arthro- scopically confirmed MCL tears.43 Some studies have attempted to compare valgus stress testing on clinical PATELLOFEMORAL INSTABILITY examination with magnetic resonance imaging (MRI) findings; in general, agreement between the 2 diagnostic meth- Anterior knee pain is among the most common ortho- ods has appeared to be no better than fair to good.85,113 paedic complaints and may be a manifestation of instabil- Recommended Technique. The patient is placed supine ity at the patellofemoral joint. Other symptoms of with the hip of the affected limb slightly abducted and the patellofemoral instability can include crepitus, buckling, knee flexed to 30° over the side of the table. The examiner swelling, difficulty climbing or descending stairs or squat- positions one hand over the lateral aspect of the knee and ting, and “slipping” of the patella.6 There may be a history grasps the ankle with the other hand. A valgus stress is of trauma, although patellofemoral instability can also applied. The test is then repeated in full extension.79 result from congenital factors. Unlike the aforementioned Grading the valgus stress test incorporates both the ligamentous instabilities, patellofemoral instability is amount of medial joint opening and the quality of the end- multifactorial, and although recent focus has been on defi- point. Grade I is assigned to knees with 5 mm or less of ciency of the medial patellofemoral ligament (MPFL),99 joint opening and a solid endpoint, grade II corresponds to patellofemoral instability cannot be attributed to the dys- a 6 mm to 10 mm opening with a good endpoint, and grade function of a single ligament or anatomic structure alone. III represents >10 mm of opening and a soft endpoint.50 Yet, because the symptoms and signs of a patient present- At 30° of flexion, the PMC and POL provide relatively little ing with acute patellofemoral instability—“my knee buck- resistance to valgus stress, and the superficial MCL has a much led and swelled”—may be confused with other ligamentous more important role. Accordingly, maximum instability at 30° injuries, consideration of patellofemoral instability within

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 Vol. 36, No. 3, 2008 Knee Physical Exam 591 the spectrum of ligamentous instability of the knee joint is warranted. The anatomy and biomechanics of the entire lower extrem- ity must be taken into account when evaluating a patient with patellofemoral instability. In addition to targeting the dynamics of the knee joint, gait and stance must be assessed, as must varus or valgus and rotational alignment of the limb. Although it is beyond the scope of this article to describe completely the biomechanics of patellofemoral instability, some common anatomic features and selected methods of evaluation will be considered. Notably, in addition, lateral facet compression syndrome and patellar tilt are not synonymous with patellofemoral instability; evaluation for signs of anterior knee pain not related to patellofemoral instability is not the purpose of this review. Factors contributing to patellofemoral joint instability may include excessive quadriceps angle (Q-angle), femoral anteversion, external tibial torsion, patella alta, femoral trochlea or patellar dysplasia, generalized laxity, pes planus, vastus medialus obliquus (VMO) atrophy, MPFL insufficiency, and genu valgum.6,35,36 The VMO is a dynamic stabilizer of the patella and acts to balance laterally directed forces on the patella at the trochlea. The MPFL is a primary soft-tissue structure that checks lateral patellar motion and is often found to be injured in a traumatic lateral patellar dislocation. Sallay et al99 described the pathoanatomy of patellar dislocation and reported MRI evidence of medial patellofemoral ligament tears in 87% of 19 patients, with increased signal intensity adjacent to the adductor tubercle in 96% and within the VMO in 78%. Bony configurations of the lateral patellar facet and the lateral femoral condyle also influence patellofemoral sta- Figure 19. Quadriceps angle (for patellofemoral instability). bility. Normally, in the axial plane, the anterior lateral With the patient supine and the right knee at 0° and then condylar border lies 1 cm anterior to the border of the medial flexed to 90°, a goniometer is used to measure the angle condyle. Furthermore, the lateral facet of the patella is usu- from the anterior superior iliac spine to the center of the ally longer and more acutely sloped than the medial facet. reduced patella to the center of the tibial tuberosity. This contributes to static patellofemoral stability, and derangements of these features may cause patellofemoral 10° in men. Greater angles increase laterally directed 37 pathology. forces on the patella through the pull of the patellar ten- The spectrum of instability ranges from patellar mal- don. The Q-angle is typically measured on the supine tracking to frank, typically lateral, dislocation. Patients with patient whose hips and knees are in neutral position.9,84 A “miserable malalignment” syndrome have pathologic inter- Q-angle should also be assessed with the patient in a sit- nal femoral rotation as a result of excessive femoral neck ting position with knees flexed at 90°. If the Q-angle is anteversion. Normally, femoral anteversion is defined as 11° measured in extension, the examiner must first reduce the 53 with a standard deviation of 7°. Excessive femoral ante- patella in the trochlear groove. A laterally subluxated version can cause the trochlea to rotate medially when the patella will result in measurement of a falsely low Q-angle. hip is placed in neutral rotation. These patients also have a Especially in patients with rotationally lax knees, an large Q-angle (discussed below) produced by both associated apparently normal Q-angle in the supine position and knee external tibial torsion and pes planus, resulting in over- extension may be abnormal in a more functional position pronation. Signs of this disorder include the “bayonet sign,” of knee flexion with external rotation applied to the tibia.66 which refers to a sharp varus deformity of the proximal Furthermore, at 90° of flexion, the patella is engaged and third tibia, and “squinting patellae,” in which the patellae centered in the trochlear groove,95 minimizing risk of a 9 face each other when the patient’s feet are held parallel. falsely low Q-angle measurement. Recommended Technique. With the patient supine, the Q-Angle Assessment examiner marks the center of the tibial tuberosity. Next, while the patient relaxes, the examiner centers the patella The Q-angle refers to the angle created by a line drawn in the trochlear groove and marks the center of the from the anterior superior iliac spine (ASIS) to the center reduced patella. Finally, the examiner locates the ASIS of the patella and from the center of the patella to the tib- and places the patient’s extended index finger as a marker ial tuberosity. A normal Q-angle is up to 15° in women and of the ASIS. A goniometer is used to measure the angle

Downloaded from ajs.sagepub.com at Aarhus Universitets Biblioteker / Aarhus University Libraries on December 30, 2010 592 Lubowitz et al The American Journal of Sports Medicine from the ASIS to the center of the reduced patella to the evaluating patellar dislocation. In a positive test result, as pas- center of the tibial tuberosity. Q-angle assessment is illus- sive lateral patellar translation commences as described in the trated in Figure 19. manual translation test above, the patient becomes visibly uncomfortable and apprehensive, begins to resist patellar sub- Assessment of Patellar Tracking and the J-Sign luxation with quadriceps muscle tension, and attempts to flex the knee and pull the patella back into a reduced position.49,79 The patella is engaged in the trochlear groove in knee flexion. Recommended Technique. The patient is placed in the Thus, during active flexion, the patella may be observed to supine position, and the quadriceps is relaxed. The knee is engage the femoral trochlea (reduce) smoothly at approxi- fully extended (although Fairbank described that the test mately 30° to 40° of flexion. Delayed trochlear engagement or should be performed in 30° of knee flexion). The examiner abrupt shifts of the patella (out of the trochlea on knee exten- places both thumbs on the medial border of the patella and sion or into the trochlea with knee flexion) correspond to a slowly and gently attempts to displace the patella laterally. positive J-sign representing a J-shaped path of the patella rel- The patient’s reaction is noted. No pain is normal, but pain ative to the trochlea. The patella and tibia show translation, during the maneuver, while notable, does not represent a rotation, and excursion within established ranges. Normal positive test finding. Rather, frank patient apprehension, patellar translation ranges from 17 mm laterally to 4 mm or patient expression of fear that the patella will dislocate, medially.6,9,29 The J-sign suggests excessive lateral patellar represents a positive test result. tracking due to unbalanced and excessive lateral forces acting on the patella. Such pathologic changes may predispose the patella to subluxation or dislocation. CONCLUSION Recommended Technique. With the patient in a sitting Accurate diagnosis is the hallmark of appropriate treat- position, the examiner simply observes patellar motion as ment, and by taking into consideration both structure and the patient extends the leg from 90° of knee flexion to full function, an orthopaedic surgeon’s ability to diagnose pat- extension or cyclically straightens and bends the knee. terns of knee injury is enhanced. Abrupt or extreme lateral shift of the patella represents a positive J-sign. ACKNOWLEDGMENT Manual Translation Test The authors acknowledge Henry P. Hackett and Wylie The manual translation test evaluates lateral patellar Elson, MD, for their editorial support. mobility. Reversal of this maneuver can be used to assess 9 medial patellar displacement. Carson et al believe that REFERENCES the patella should not displace in either direction more than one half the width of the patella. Others have 1. Bach BR, Russell WF, Wickiewicz TL. The pivot shift phenomenon: described a grading scheme for patellar translation in results and description of a modified clinical test for anterior cruciate which the width of the patella is divided into quadrants. ligament insufficiency. Am J Sports Med. 1988;16:571-576. Lateral displacement of no more than 2 quadrants is 2. Bach BR Jr, Warren RF, Flynn WM, Kroll M, Wickiewiecz TL. Arthrometric evaluation of knees that have a torn anterior cruciate within normal limits. Lateral displacement of 3 quadrants ligament. 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