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Lower Extremity Trauma MCQs

Practice Set 31 of 34

This practice set contains high-yield board review questions covering key concepts in Lower Extremity Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 601

Topic: Lower Extremity Trauma
A 32-year-old male sustains a high-energy trauma to his left knee. Radiographs and CT scans reveal a bicondylar tibial plateau fracture with a transverse fracture line separating the metaphysis from the diaphysis. What is the correct Schatzker classification for this injury?
. Schatzker II
. Schatzker IV
. Schatzker V
. Schatzker VI
. Schatzker III

Correct Answer & Explanation

. Schatzker VI

Explanation

The Schatzker classification is widely used for tibial plateau fractures. Schatzker I, II, and III are lateral plateau fractures (split, split-depression, pure depression). Schatzker IV involves the medial plateau. Schatzker V is a bicondylar fracture where the metaphysis remains in continuity with the diaphysis. Schatzker VI is defined by metaphyseal-diaphyseal dissociation (complete separation of the joint block from the shaft), typically due to high-energy trauma.

Question 602

Topic: Lower Extremity Trauma

The pivot shift test is pathognomonic for ACL insufficiency. During the maneuver, the tibia translates anteriorly in extension and reduces with a 'clunk' as the knee is flexed. Which anatomical structure is primarily responsible for generating the reducing force during flexion?

. Semimembranosus
. Popliteus
. Biceps femoris
. Iliotibial band
. Medial collateral ligament

Correct Answer & Explanation

. Semimembranosus

Explanation

In an ACL-deficient knee, the tibia subluxates anteriorly in extension. As the knee is flexed past 20-30 degrees, the Iliotibial (IT) band shifts from being an extensor of the knee to a flexor, falling posterior to the axis of rotation and creating a posterior vector that pulls the lateral tibial plateau backward into the reduced position.

Question 603

Topic: Lower Extremity Trauma

The pivot shift test is utilized to evaluate rotatory instability of the knee. Biomechanically, what occurs during a positive pivot shift test as the knee is brought from full extension into flexion?

. The medial tibial plateau reduces from an anteriorly subluxated position
. The lateral tibial plateau reduces from an anteriorly subluxated position
. The lateral tibial plateau subluxates anteriorly
. The patella subluxates laterally out of the trochlea
. The posterior tibia reduces from a posteriorly subluxated position

Correct Answer & Explanation

. The medial tibial plateau reduces from an anteriorly subluxated position

Explanation

In an ACL-deficient knee, the lateral tibial plateau rests in an anteriorly subluxated position in full extension. As the knee flexes past 20-30 degrees, the iliotibial band transitions from an extensor to a flexor, applying a posterior vector that suddenly reduces the lateral plateau with a palpable clunk.

Question 604

Topic: Lower Extremity Trauma

During the pivot shift test for anterior cruciate ligament (ACL) insufficiency, the examiner applies a valgus stress and internal rotation while flexing the knee. The distinct clunk observed at 20-30 degrees of flexion represents which biomechanical event?

. Subluxation of the medial tibial plateau
. Reduction of the anteriorly subluxated lateral tibial plateau by the iliotibial band
. Subluxation of the lateral tibial plateau
. Reduction of the medial tibial plateau by the pes anserine
. Impingement of the ACL stump against the PCL

Correct Answer & Explanation

. Subluxation of the medial tibial plateau

Explanation

During the pivot shift test, the tibia is subluxated anteriorly in extension. As the knee flexes past 20-30 degrees, the iliotibial band transitions from an extensor to a flexor, rapidly reducing the lateral tibial plateau.

Question 605

Topic: Lower Extremity Trauma
A 45-year-old pedestrian is struck by a motor vehicle and sustains a severe right knee injury. Radiographs and CT imaging demonstrate a bicondylar fracture involving both the medial and lateral tibial plateaus, with complete dissociation of the articular surfaces from the underlying tibial diaphysis. According to the Schatzker classification, what is the grade of this fracture?
. Schatzker III
. Schatzker IV
. Schatzker V
. Schatzker VI

Correct Answer & Explanation

. Schatzker VI

Explanation

The Schatzker classification divides tibial plateau fractures into six types. Schatzker V is a bicondylar fracture but maintains continuity between the epiphysis/metaphysis and the diaphysis. Schatzker VI involves a bicondylar fracture with complete metaphyseal-diaphyseal dissociation, separating the articular block from the shaft.

Question 606

Topic: Lower Extremity Trauma

In the evaluation of intra-articular calcaneus fractures, the Sanders classification is highly prognostic for clinical outcomes. Which specific imaging view is primarily used to determine the Sanders classification?

. Lateral radiograph of the foot
. Harris axial radiograph
. Sagittal CT reconstruction
. Coronal CT image through the widest part of the posterior facet
. Axial CT image at the level of the sustentaculum tali

Correct Answer & Explanation

. Lateral radiograph of the foot

Explanation

The Sanders classification relies on coronal CT images. Specifically, it uses the coronal slice that displays the widest portion of the posterior facet of the calcaneus (sustentaculum tali to the lateral wall) to identify the number and location of primary fracture lines through the articular surface.

Question 607

Topic: Lower Extremity Trauma
What is the primary determinant used to classify intra-articular calcaneus fractures according to the Sanders classification?
. The degree of Bohler's angle depression on the lateral radiograph
. The number and location of articular fragments on the coronal CT scan at the widest aspect of the posterior facet
. The degree of comminution of the anterior process on the axial CT scan
. The angle of Gissane on the plain lateral radiograph
. The involvement and displacement of the calcaneocuboid joint

Correct Answer & Explanation

. The number and location of articular fragments on the coronal CT scan at the widest aspect of the posterior facet

Explanation

The Sanders classification is based strictly on coronal CT scan images. It dictates the number of articular fragments of the posterior facet at its widest point. Type I is non-displaced; Type II is two-part; Type III is three-part; Type IV is four or more parts (highly comminuted).

Question 608

Topic: Lower Extremity Trauma

A 26-year-old skier presents with posterolateral ankle pain and a snapping sensation behind the lateral malleolus. Ultrasound confirms anterior subluxation of the peroneal tendons out of the retromalleolar groove during active ankle dorsiflexion and eversion. Which anatomical structure is primarily incompetent in this condition?

. Inferior extensor retinaculum
. Superior peroneal retinaculum
. Calcaneofibular ligament
. Posterior talofibular ligament
. Peroneus brevis tendon

Correct Answer & Explanation

. Inferior extensor retinaculum

Explanation

The superior peroneal retinaculum (SPR) is the primary restraint against anterior subluxation of the peroneal tendons. Injury or avulsion of the SPR from the fibula (often accompanied by a 'fleck sign' on radiographs) leads to dynamic subluxation of the tendons over the lateral malleolus.

Question 609

Topic: Lower Extremity Trauma

During deep flexion of the normal native human knee joint, how does the center of rotation of the distal femur move relative to the tibial plateau?

. Anteriorly
. Posteriorly
. Medially
. Laterally
. Superiorly

Correct Answer & Explanation

. Anteriorly

Explanation

During normal knee flexion, the femoral condyles exhibit 'posterior rollback' relative to the tibia. This kinematic mechanism, primarily driven by the posterior cruciate ligament (PCL) and meniscal geometry, maximizes flexion by delaying posterior impingement between the femur and the posterior tibial plateau.

Question 610

Topic: Lower Extremity Trauma

A 2-year-old girl is evaluated for bilateral genu varum. Which radiographic finding is most predictive of progression to infantile Blount disease rather than physiologic bowing?

. Metaphyseal-diaphyseal angle of Drennan greater than 16 degrees
. Tibiofemoral angle of 10 degrees
. Medial cortical thickening of the tibia
. Presence of a proximal tibial metaphyseal beak
. Physeal widening at the distal femur

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle of Drennan greater than 16 degrees

Explanation

A metaphyseal-diaphyseal angle (MDA) of Drennan greater than 16 degrees has a high positive predictive value for progression to infantile Blount disease. Angles less than 10 degrees typically resolve spontaneously as physiologic bowing.

Question 611

Topic: Lower Extremity Trauma

A 45-year-old male sustains a high-energy knee injury. Radiographs and CT demonstrate a fracture of the medial tibial plateau with significant depression, as well as a separate fracture line extending into the lateral plateau. What is the correct Schatzker classification?

. Schatzker II
. Schatzker IV
. Schatzker V
. Schatzker VI
. Schatzker VII

Correct Answer & Explanation

. Schatzker II

Explanation

Schatzker V designates a bicondylar tibial plateau fracture. The presence of both medial and lateral plateau involvement makes it a Type V. Type VI would involve complete metaphyseal-diaphyseal dissociation. Type IV is an isolated medial plateau fracture.

Question 612

Topic: Lower Extremity Trauma

A 10-year-old boy is evaluated for a suspected limb length discrepancy. Bone age is calculated, and the multiplier method is used. On average, how much longitudinal growth is contributed per year by the distal femoral and proximal tibial physes, respectively?

. 6 mm and 4 mm
. 9 mm and 6 mm
. 12 mm and 9 mm
. 15 mm and 10 mm
. 3 mm and 2 mm

Correct Answer & Explanation

. 6 mm and 4 mm

Explanation

The distal femur contributes approximately 9 mm per year, and the proximal tibia contributes approximately 6 mm per year to longitudinal growth. This rule of thumb is critical for timing epiphysiodesis procedures.

Question 613

Topic: Lower Extremity Trauma

A 6-year-old girl complains of a snapping sensation and pain on the lateral side of her knee. MRI reveals a thickened meniscus that covers the entire lateral tibial plateau. During arthroscopy, the meniscus lacks posterior capsular attachments. What is the name of this specific variant?

. Incomplete discoid meniscus
. Complete discoid meniscus
. Wrisberg variant discoid meniscus
. Meniscal cyst
. Bucket-handle meniscal tear

Correct Answer & Explanation

. Incomplete discoid meniscus

Explanation

The Wrisberg variant of a discoid lateral meniscus lacks normal posterior coronary ligament attachments. It is solely tethered by the meniscofemoral ligament of Wrisberg, making it highly hypermobile and responsible for the classic 'snapping knee' syndrome.

Question 614

Topic: Lower Extremity Trauma

During a posterior cruciate-retaining TKA, the surgeon enthusiastically resects the posterior aspect of the tibial plateau, accidentally injuring the popliteal artery. Anatomically, at what level relative to the joint line is the popliteal artery positioned closest to the posterior capsule?

. Exactly at the level of the knee joint line
. 1 cm proximal to the joint line
. 1 cm distal to the joint line
. 3 cm proximal to the joint line
. 3 cm distal to the joint line

Correct Answer & Explanation

. Exactly at the level of the knee joint line

Explanation

The popliteal artery lies closest to the posterior capsule directly at the level of the knee joint line. It is tethered proximally by the adductor hiatus and distally by the soleus arch, making it highly susceptible to injury during the tibial cut or overly aggressive posterior capsular releases.

Question 615

Topic: Lower Extremity Trauma

When planning a medial opening-wedge high tibial osteotomy (HTO) for a 45-year-old male with medial compartment osteoarthritis and varus malalignment, the mechanical axis (weight-bearing line) is typically shifted to pass through a specific target point on the tibial plateau. What is the generally accepted target location (Fujisawa point) measured from the medial edge of the tibial plateau?

. 30%
. 40%
. 50%
. 62.5%
. 80%

Correct Answer & Explanation

. 62.5%

Explanation

The Fujisawa point is the optimal target for the mechanical axis following an HTO for medial compartment osteoarthritis. It is located at 62.5% of the tibial plateau width from the medial edge (slightly lateral to the lateral tibial spine), which moderately unloads the diseased medial compartment by shifting the weight-bearing axis into the healthy lateral compartment.

Question 616

Topic: Lower Extremity Trauma

A 68-year-old male undergoes a primary TKA. During intraoperative trialing, the knee is completely stable in extension but exhibits significant laxity to varus and valgus stress at 90 degrees of flexion. Which of the following steps is the most appropriate next maneuver to balance the knee?

. Upsize the femoral component to increase the anteroposterior dimension
. Recut the distal femur to remove more bone
. Release the posterior cruciate ligament (PCL)
. Downsize the femoral component and use a thicker polyethylene insert
. Increase the posterior slope of the tibial cut

Correct Answer & Explanation

. Upsize the femoral component to increase the anteroposterior dimension

Explanation

Flexion instability (laxity in flexion but stable in extension) implies a flexion gap that is larger than the extension gap. To decrease the flexion gap without altering the extension gap, the surgeon can upsize the femoral component (increasing the posterior condylar offset/AP dimension) and use an offset tibial poly or shift the component posteriorly. Alternatively, translating the same-sized femoral component posteriorly decreases the flexion gap. Recutting the distal femur would increase the extension gap (making it symmetric but overall loose, requiring a thicker poly). Increasing posterior slope increases the flexion gap, worsening the instability.

Question 617

Topic: Lower Extremity Trauma

The anterolateral ligament (ALL) of the knee is an important secondary stabilizer against internal tibial rotation. It originates near the lateral femoral epicondyle. What is its precise anatomical insertion on the tibia?

. Gerdy's tubercle
. The fibular head
. Midway between Gerdy's tubercle and the fibular head
. The anterior margin of the iliotibial band insertion
. The posterior aspect of the lateral meniscus

Correct Answer & Explanation

. Midway between Gerdy's tubercle and the fibular head

Explanation

The anterolateral ligament (ALL) originates from the lateral femoral epicondyle (slightly anterior and distal to the FCL origin) and inserts on the lateral tibial plateau, exactly midway between Gerdy's tubercle and the fibular head. It is deep to the iliotibial band.

Question 618

Topic: Lower Extremity Trauma

Regarding rotational alignment in TKA, which anatomical landmark is considered the most reliable guide for external rotation of the femoral component?

. Whiteside's line (Perpendicular to the transepicondylar axis)
. Posterior condylar line (Parallel to the posterior femoral condyles)
. Trans-epicondylar axis (TEA)
. Anterior-posterior axis (AP axis)
. Femoral shaft axis

Correct Answer & Explanation

. Trans-epicondylar axis (TEA)

Explanation

The Transepicondylar Axis (TEA) is considered the most reliable and anatomically consistent reference for femoral component rotation, representing the functional flexion axis of the knee. The femoral component is typically aligned parallel or slightly externally rotated (3-5 degrees) to the TEA. Whiteside's line (or the anteroposterior axis) is perpendicular to the TEA. The posterior condylar line can be unreliable in osteoarthritic knees due to posterior condylar wear. The femoral shaft axis guides coronal alignment, not rotation.

Question 619

Topic: Lower Extremity Trauma

In a TKA for a severe varus deformity, what is a common pitfall in tibial component placement regarding coronal alignment, if not properly addressed?

. Placing the tibial component in excessive valgus
. Placing the tibial component in varus, parallel to the resected bone surface
. Placing the tibial component with excessive anterior slope
. Over-resection of the lateral tibial plateau
. Under-resection of the medial tibial plateau

Correct Answer & Explanation

. Placing the tibial component in varus, parallel to the resected bone surface

Explanation

In a severe varus knee, the medial tibial plateau is typically worn and depressed. If the surgeon simply resects bone parallel to this worn surface, the tibial component will inadvertently be placed in varus, which is a common cause of early loosening. The goal is to create a neutral or slight valgus (0-3 degrees) alignment relative to the mechanical axis of the tibia, which requires resecting more bone from the intact (lateral) side relative to the worn (medial) side, or using proper alignment guides. Over-resection of the lateral tibial plateau could lead to valgus malalignment, but the most common pitfall whennot properly addressedis varus.

Question 620

Topic: Lower Extremity Trauma

Which rotational guide for the femoral component is considered 'anatomic' and least affected by femoral condylar wear?

. Posterior Condylar Axis
. Whiteside's Line (AP axis)
. Trans-epicondylar Axis (TEA)
. Anterior Condylar Axis
. Femoral Shaft Axis

Correct Answer & Explanation

. Trans-epicondylar Axis (TEA)

Explanation

The Transepicondylar Axis (TEA), connecting the most prominent points of the medial and lateral epicondyles, is considered the most anatomically consistent and reliable reference for femoral component rotation. It represents the functional flexion-extension axis of the knee and is least affected by femoral condylar wear compared to the posterior condylar axis. Whiteside's Line (AP axis) is perpendicular to the TEA. The femoral shaft axis relates to coronal alignment.

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