Clinical examination of the knee: know your tools for diagnosis of knee injuries
© Rossi et al; licensee BioMed Central Ltd. 2011
Received: 24 March 2011
Accepted: 28 October 2011
Published: 28 October 2011
The clinical evaluation of the knee is a fundamental tool to correctly address diagnosis and treatment, and should never be replaced by the findings retrieved by the imaging studies carried on the patient.
Every surgeon has his own series of exams with whom he is more confident and on whom he relies on for diagnosis. Usually, three sets of series are used: one for patello-femoral/extensor mechanism pathologies; one for meniscal and chondral (articular) lesions; and one for instability evaluation.
This review analyses the most commonly used tests and signs for knee examination, outlining the correct way to perform the test, the correct interpretation of a positive test and the best management for evaluating an injured knee both in the acute and delayed timing.
The introduction of highly effective imaging tools like Computed Tomography and Magnetic Resonance in the clinical practice in Orthopaedics and Traumatology has stolen the central role of clinical evaluation, so that nowadays there's a common feeling, between patients but also between surgeons, that the diagnosis of a thorn meniscus or a ruptured ACL has to be ruled out only on the basis of an imaging study.
But the efficacy and affordability of a correct clinical examination needs not to be forgotten: this paper presents an overview of the most known tests and signs for knee examination, grouped in the three aspects of knee injuries: 1) patello-femoral joint/extensor mechanism; 2) articular (meniscal and chondral) lesions; and 3) knee instability.
In all cases, the clinical evaluation should be introduced by a careful interview of the patient, in order to address the subsequent exam to the affected area of the knee, and to choose the correct series of tests and signs.
The beginning of the interview should be carried in order to 1) localize the pain/dysfunction in one aspect of the knee (extensor mechanism; articular: medial vs lateral vs patellofemoral; ligaments on the medial vs lateral compartment vs central pivot); 2) define the timing of onset of the injury/dysfunction: acute vs previous injury; chronic disease; overuse; 3) collect the actual symptoms felt by the patient: pain vs discomfort vs disability.
Extensor mechanism pathology is often related to a chronic, repetitive trauma. Nevertheless, recent injuries should be enquired, as anterior knee pain can be associated to a recent patellar subluxation or dislocation, or to ruptured patellar or quadriceps tendons, particularly in older patients.
Anterior pain during activity and at rest is mostly associated with chondral lesions, while pain associated with prolonged flexion can be raised by a slight instability or malalignement.
Meniscal lesions are almost always consequence of a single trauma, but chronic lesions and degenerative tears of the menisci as well as chondral defects secondary to overuse should not be forgotten. The interview should be focused on the mechanism of injury (direct trauma, sprain, complex trauma) and on the pre-existing condition of the knee (e.g. previous injuries, history of overuse). Most patients do not report a real trauma, but rather an acute pain occurred after a weight-bearing twist on the knee or a knee flexion.
Locking of the knee is usually associated with bucket handle tears of the meniscus, and must be carefully inquired. An haemorrhage around the posterior capsule and medial collateral ligament, with subsequent hamstring spasm can mimic a locking. Snaps, clicks, catches or jerks can be reported by the patients and the examiner should try to reproduce them with the manipulative manoeuvres.
Painful giving away of the knee is a common symptom, and is often reported as caused associated to rotatory movements and often associated with a feeling of "the joint jumping out of place". This symptom is non-specific and also reported in case of loose bodies, patellar chondromalacia, instability, quadriceps weakness.
In case of instability, the onset of the lesion can most of the times be related to a single injury, and the patient usually remembers it. However, it is often difficult to recall the exact mechanism of injury, and the patient should be forced in trying to reproduce the "twist" or impact sustained by the knee at the time of the injury: this can strongly help in estimating the anatomic structure(s) involved in the lesion. Additionally, the rupture of ligament such as ACL and PCL produces many times an audible "snapping" or "cracking" sound: the patient should be questioned if he/she heard such a sound.
The clinical examination of a knee is addressed to evaluate three aspects: 1) patello-femoral joint/extensor mechanism; 2) articular (meniscal and chondral) lesions; and 3) knee instability.
The series of the most known exams, signs and tests used for each of the three aspects will be here discussed.
The Q-angle is the intersection between a line drawn from the anterior superior iliac spine to the center of the patella and a line drawn from the center of the tibial tubercle to the center of the patella. The angle can be measured in full knee extension, but the patella had better be centered in the trochlear groove to be more stable; therefore it is recommend to measure the Q-angle at 30° of knee flexion to move the patella into the proximal portion of the trochlea. The range of normality is usually considered 10° to 20°. An increased Q-angle may indicate a tendency to lateral tilt or glide. However, the clinical usefulness of the Q-angle is debated, and it has been reported no correspondence between Q-angle and PF pain measurements with patients' clinical symptoms . A sitting Q angle (tubercle sulcus angle) has been advocated to better represent the relationship between the patellar and quad tendon vectors. An increased Q-angle (15°-20°) is associated to lateral patellar subluxation . It has been noted that a static measure should not be used to assess a dynamic condition such as PF maltracking. It is still debated whether Q-angle correlates to PF pain syndrome  or not , and as far as this topic is still unclear, the Q-angle alone should never be used as a diagnostic tool for PF joint pathology.
Patellar Tilt and Glide
Patellar tilt and glide are often cited together, and many times are considered synonyms. Actually the patellar tilt indicates tightness of lateral restraints; it is performed with the patient supine with the knee in full extension. If the lateral side of the patella can not be elevated above the horizontal the test is positive.
A careful observation of patella tracking is mandatory, to rule out any muscular/ligamentous deficiency.
The quadriceps muscle is composed by: the rectus femoris and vastus intermedius muscles, that apply an axial load to the patella; the vastus lateralis and vastus medialis which have oblique insertions pull the patella in either direction.
The medial retinaculum and the lateral retinaculum act as static constraint to patella tracking.
The tracking of the patella from full extension into flexion should be recorded visually, and should be smooth, without abrupt or sudden movements. During knee flexion the patella moves more centrally and the facets increase their contact with femoral condyles. The iliotibial band has an expansion to the lateral retinaculum, and during the knee flexion determines a lateralization of the patella. Lateralization of the patella during flexion can be determined by weakness of medial muscles and retinaculum, or tightness of lateral structures.
Additionally, the patella engages the femoral condyles (the trochlea) at about 20 to 30 degrees of knee flexion: in case of condyles hypoplasia the facets do not engage in the trochlea and the patella can glide easily.
Besides maltracking, any articular pain or crackling can be elicited by applying pressure on the patella during flexion and extension: this does not always indicate PF chondromalacia, but other causes of pain must be considered, such as neuroma, patellar tendonitis, plica, referred pain, meniscus derangement, synovitis, and osteocondritis dissecans .
When the patella is subluxated laterally and, it suddenly shifts medially, when engaging the femoral trochlea, following a J shaped path. This sign indicates excessive lateral patellar shift in terminal extension ; external rotation facilitate its identification .
2. Meniscal and chondral lesions
A meniscal tear can be difficult to diagnose, as symptoms are mostly non-specific and other injuries can disguise the meniscal lesion. A meniscal lesion has to be suspected every time in case of pain occurred after a weight-bearing sprain of the knee or after a prolonged squatting or a real trauma.
Chondral lesions are more often related to chronic degeneration, but acute lesions can also occur.
As the menisci have no direct innervation, pain is related to synovitis in the adjacent capsular and synovial tissues, as it happens for chondral lesions. Thus, discriminating between meniscal and chondral lesions can be sometimes difficult.
Crepitation during flexion and extension against resistance may indicate cartilage pathology. The patient may walk with an externally rotated gait to avoid contact of the medial femoral condyle with the medial tibial spine in case of chondral lesion at that level.
All tests for meniscal and chondral lesions are a combination of knee flexion, tibial rotation and a stress on the joint line: this is the position where the posterior condyles roll back and the joint space becomes narrow, tightly engaging the menisci.
The tests can be dived in palpation test (McMurray's, Bragard's, Steinmann's second, figure of four meniscal stress manoeuvre) and rotation test (Apley's, Bohler's, duck walking, Helfet's, Merke's, Payr's, Steimann's first) .
Meniscal Palpation Tests
In Bragard's test, external tibial rotation and knee extension bring the meniscus more anterior: if tenderness is felt along the joint line palpation, an articular surface irregularity (i.e. chondral lesion) or a meniscal tear is suspected.
In Steinmann's second test joint line tenderness migrates posteriorly with knee flexion and anteriorly with knee extension, following the movements of the meniscus.
Meniscal Rotation Tests
In Bohler's test a varus stress and a valgus stress are applied to the knee: pain is elicited by compression of the meniscal tear.
Squat test, duck walking test and Thessaly test consist in several repetitions of full weightbearing flexions on the knee, in different positions (squatting, walking in full flexion, and at 5 and 20° flexion, respectively) .
Merke's test is similar to Thessaly test performed with the patient in a weightbearing position: pain with internal rotation of the body produces an external rotation of the tibia and medial joint line pain when medial meniscus is torn. The opposite occurs when lateral meniscus is torn.
In Helfet's test the knee is locked, and cannot rotate externally while extending, and the Q angle cannot reach normality with extension.
In Peyr's test the patient is asked to sit in Turkish position, thus stressing the medial joint line: if the position raises pain, the test is positive for a medial meniscal lesion.
In Steinmann's first test the knee is held flexed at 90° and forced to external rotation, then internal rotation: the test is positive for medial meniscal tear if raises pain upon externally rotating, while it is positive for lateral meniscal tears in case of pain during internal rotation.
3. Knee Instability
Instability is usually defined with a direction (anterior, posterior, medial, lateral, rotatory), which is the position the proximal tibia can abnormally reach, with respect to the distal femur. The direction of instability depends on the single, or multiple, structures involved: the main structures involved in knee (in)stability are: ACL, PCL, MCL, LCL, posterolateral corner and posteromedial corner.
Many manoeuvres are available to rule out the type of instability and test the knee structures involved. All tests can be divided in 4 groups: stress tests, slide tests, pivot shift (jerk) tests and rotational tests [6, 9, 10, 12].
The standard stress tests include valgus (abduction) and varus (adduction) tests; additionally, Cabot manoeuvre is a commonly used stress test.
Cabot's manoeuvre is another stress test, that evaluates the LCL. The knee is held in a 'figure of four' position, while giving a varus stress to the joint: the LCL, when intact, can be distinctively palpated as a tight chord stretched between the fibular head and the lateral epicondyle.
While keeping the patient's knee in this position the figure of four meniscal stress manoeuvre can also be perfomed (for details, see previously: figure of four meniscal stress manoeuvre).
With these tests the examiner slides the tibia, trying to subluxate it from the distal femur.
Anterior and Posterior Drawer Test: the most commonly used test for ACL and PCL evaluation, they are easy to perform, but require some attention to avoid mistakes and for correct interpretation. The tests have to be carried out in three different tibial rotational positions: neutral and at 30° of internal and external rotation. Internal rotation tightens the PCL and the posterolateral corner, so that the anterior drawer can become negative in this position. Anterior and posterior drawer test are performed simultaneously, and the examiner has to take care to rule out the amount of anterior and posterior tibial translation. Indeed in some cases when a PCL deficient knee has a posteriorized starting position, the reduction to a neutral postion can mimic an anterior drawer test: careful evaluation is required to avoid this mistake. In order to determine the correct starting point, palpation can be useful: in the neutral position the tibial plateau and the medial condyle face one another, with a slight anterior step-off of the tibia (approximately 0.5 - 1 cm); this has to be taken as the "zero point" for anterior and posterior drawer evaluation.
In an acutely swollen knee the test can be done keeping the knee in a less flexed position, at 60 to 80° thus avoiding excessive pain due to haemarthrosis.
The use of mechanical quantification of the tibial translation with measure instruments such as the KT-1000 (R) is useful for follow-up but not for diagnostic purposes.
The posterior Lachman test evaluates the PCL, with less efficacy than anterior Lachman.
In the Lachman-type position, the patient is asked to lift his leg against resistance (Active Resisted Extension Test).
In the drawer-type position, the patient is asked to lift his leg against resistance (Active Resisted Extension Test II), or contraction of quadriceps muscle is obtained by evoking the patellar reflex (Patellar Reflex Reduction Test).
Pivot Shift (jerk) Tests
These tests evaluate the rotatory instability that affects ACL deficient patients: this determines discomfort or frank pain with a shift or jerk of the knee joint, usually felt when squatting or changing direction.
An isolated ACL rupture produces a slight shift, often highly uncomfortable for the patients, while a posterolateral corner lesion is required to determine a huge, visible and sometimes audible jerk.
These tests are painful, and most of the times after the first attempt the test is no more reproducible, but they are the most effective in detecting an ACL rupture. In the hours before the injury, as the knee starts to swell, the tests becomes more and more difficult to be performed, and painful, so it has to be carried out in the most acute setting or in the chronic one.
McIntosh firstly described the test as the 'pivot shift' test (McIntosh's Pivot Shift (Jerk) Test), quoting a hockey player with an unstable ACL deficient knee who reported: -when I pivot, my knee shifts-.
In Noyes' Glide Pivot Shift Test the tibial subluxation is achieved not by internally rotating the leg, but rather by compressing the tibia axially towards the femur and lifting it anteriorly. The examiner tries to dislocate the whole tibial plateau (antero-posterior instability), not only the lateral aspect (rotatory instability), so a 'glide', rather than a clear clunk is evoked.
Hughston's Jerk Test produces the subluxation by extending the knee from the flexed position, applying the same valgus and internal rotation stress as in Noyes' test.
The Reverse Pivot Shift Sign evokes the same shift as in pivot shift signs, but for PCL deficient knees: in these cases the lateral tibial plateau subluxes posteriorly when the tibia is stressed in external rotation and valgus, and reduces in extension.
The test can also be performed in the reverse direction, from the extended reduced position to the flexed subluxed one.
External Rotation Tests
These tests evaluate the posterolateral corner: a PLC deficient knee presents an external rotatory instability. PLC lesions are often associated to ACL or PCL tears, so it not uncommon to underestimate or misdiagnose a PLC lesion; the following tests are intended to electively evaluate the posterolateral corner [13, 14].
A great amount of recurvatum suggest an associated PCL rupture.
The Posterolateral External Rotation (Drawer) Test is a combination of the posterior drawer and external rotation tests: with the knee flexed at 30° and then at 90°, the tibia is forced posteriorly and in external rotation subluxating the tibia. If subluxation occurs at 30° but not at 90° an isolated PLC injury is supposed, while if subluxation occurs also at 90° a combined PCL and PLC is suspected.
Injury patterns, and relative tests.
ACL + MCL + MM
valgus stress, anterior drawer, Lachman
ACL + LC + LM
valgus stress, anterior drawer, Lachman, pivot shift
external rotation, dial, recurvatum, posterolateral drawer
MCL + ACL + PMC
valgus stress, posterior drawer, Lachman
Anteromedial + Anterolateral Instability
ACL + MCL + lateral capsule (PCL intact)
anterior drawer, Lachman, pivot shift, valgus stress
Posteromedial + Posterolateral Instability
ACL + MCL +PLC (PCL intact)
anterior drawer, Lachman, pivot shift, valgus stress, varus stress
This paper reviews the most known and used tests and signs for knee examination, outlining the importance of performing the tests in the correct way, in the right setting and timing and giving the correct interpretation. Knowing well these tests, the surgeon has a powerful tool for diagnosis and followup of the pathologies involving patellofemoral compartment, meniscal and chondral lesions and instability of the knee.
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