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Total Knee Arthroplasty (TKA) MCQs

Practice Set 10 of 23

This practice set contains high-yield board review questions covering key concepts in Total Knee Arthroplasty (TKA). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 181

Topic: Total Knee Arthroplasty (TKA)

Which of the following best describes the normal kinematics of the native knee that modern total knee arthroplasty (TKA) designs attempt to replicate?

. Femoral rollback with internal rotation of the tibia during flexion
. Femoral rollback with external rotation of the tibia during flexion
. Anterior femoral translation with tibial internal rotation during flexion
. Paradoxical anterior sliding of the femur during deep flexion
. Pure hinge motion with a single radius of curvature

Correct Answer & Explanation

. Femoral rollback with external rotation of the tibia during flexion

Explanation

Normal knee kinematics involve a 'screw-home' mechanism and 'femoral rollback'. As the knee goes from extension into flexion, the lateral femoral condyle rolls posteriorly more than the medial condyle, causing the femur to externally rotate relative to the tibia (or the tibia to internally rotate relative to the femur). Modern TKA designs, particularly posterior-stabilized or medial-pivot designs, attempt to recreate this native femoral rollback and tibial internal rotation to optimize flexion and patellar tracking.

Question 182

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female is 1-year post-operative from a primary total knee arthroplasty (TKA). She complains of anterior knee pain and a feeling that her kneecap is 'popping out.' Examination and CT imaging demonstrate significant internal rotation of the femoral component relative to the epicondylar axis, as well as internal rotation of the tibial component relative to the tibial tubercle. This combined malrotation is most predictably associated with which of the following patellofemoral complications?

. Increased patellar height (patella alta)
. Medial patellar subluxation
. Lateral patellar subluxation
. Increased patellofemoral jump distance
. Patellar clunk syndrome

Correct Answer & Explanation

. Lateral patellar subluxation

Explanation

Internal rotation of the femoral and tibial components in TKA functionally increases the Q-angle. Internal rotation of the femoral component moves the trochlear groove medially, while internal rotation of the tibial component moves the tibial tubercle laterally relative to the trochlea. This lateralizes the extensor mechanism vector, reliably pulling the patella laterally and resulting in lateral patellar tracking, subluxation, or dislocation.

Question 183

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty, trial components are placed, and gap balancing is assessed. The knee is found to be tight in 90 degrees of flexion but perfectly balanced in full extension. Which of the following femoral component adjustments will best correct this specific imbalance?

. Decrease the thickness of the polyethylene tibial insert
. Increase the distal femoral resection
. Downsize the femoral component (decrease AP dimension)
. Upsize the femoral component (increase AP dimension)
. Decrease the posterior slope of the tibial cut

Correct Answer & Explanation

. Downsize the femoral component (decrease AP dimension)

Explanation

In TKA gap balancing, the flexion gap is primarily controlled by the anteroposterior (AP) dimension of the femoral component, while the extension gap is controlled by the distal femoral resection. If the knee is tight in flexion but balanced in extension, the flexion gap needs to be increased without affecting the extension gap. Downsizing the femoral component decreases its AP dimension (specifically taking more posterior condyle), which opens up the flexion gap while leaving the extension gap unchanged.

Question 184

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty utilizing a measured resection technique, trial components are placed. Examination of the joint reveals that the knee is well-balanced and symmetric in 90 degrees of flexion, but it is excessively tight in full extension. Which of the following is the most appropriate next step to balance the knee?

. Release the posterior cruciate ligament (PCL)
. Resect additional proximal tibia
. Downsize the femoral component
. Resect additional distal femur
. Upsize the polyethylene insert

Correct Answer & Explanation

. Resect additional distal femur

Explanation

Gap balancing in TKA requires independent adjustment of the flexion and extension gaps. If the knee is balanced in flexion but tight in extension, the extension gap is too small. Resecting additional distal femur specifically opens the extension gap without affecting the flexion gap. Resecting more proximal tibia would open both gaps. Downsizing the femur increases the flexion gap. Upsizing the poly would make both gaps tighter.

Question 185

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty (TKA), the surgeon determines the rotational alignment of the femoral component. If the surgeon chooses to use the surgical epicondylar axis (SEA) to establish rotation, what specific anatomical landmarks must be connected?

. The medial epicondylar sulcus and the most prominent point of the lateral epicondyle
. The most prominent point of the medial epicondyle and the most prominent point of the lateral epicondyle
. The center of the trochlear groove and the apex of the intercondylar notch
. The posterior-most aspects of the medial and lateral femoral condyles
. The medial collateral ligament insertion and the fibular head

Correct Answer & Explanation

. The medial epicondylar sulcus and the most prominent point of the lateral epicondyle

Explanation

Establishing correct femoral rotation is critical for patellar tracking and flexion gap balance in TKA. The Surgical Epicondylar Axis (SEA) connects the sulcus on the medial epicondyle (the origin of the deep MCL) to the most prominent point on the lateral epicondyle. This differs from the Clinical Epicondylar Axis, which connects the most prominent points of both the medial and lateral epicondyles.

Question 186

Topic: Total Knee Arthroplasty (TKA)

Following a standard primary Total Knee Arthroplasty (TKA), the surgeon notes lateral patellar maltracking during the trial reduction.

Which of the following component malrotations is most likely responsible for causing lateral patellar maltracking?

. External rotation of the femoral component and external rotation of the tibial component
. Internal rotation of the femoral component and internal rotation of the tibial component
. External rotation of the femoral component and internal rotation of the tibial component
. Internal rotation of the femoral component and external rotation of the tibial component
. Excessive lateralization of the tibial tray

Correct Answer & Explanation

. Internal rotation of the femoral component and internal rotation of the tibial component

Explanation

Lateral patellar maltracking in TKA is primarily caused by an increase in the Q-angle. Internal rotation of the femoral component medializes the trochlear groove relative to the extensor mechanism. Internal rotation of the tibial component medializes the tibial tubercle. Both errors functionally increase the Q-angle and lead to lateral patellar tracking or subluxation.

Question 187

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents with a painful popping sensation at the anterior aspect of her knee when extending from a flexed position, 12 months after a total knee arthroplasty. Which of the following implant designs is classically associated with this complication?

. Cruciate-retaining TKA
. Posterior-stabilized TKA
. Medial pivot TKA
. Unicompartmental knee arthroplasty
. Rotating hinge TKA

Correct Answer & Explanation

. Posterior-stabilized TKA

Explanation

Patellar clunk syndrome is typically associated with posterior-stabilized TKA designs. It occurs when a fibrous nodule forms at the superior pole of the patella and catches in the intercondylar box of the femoral component during extension.

Question 188

Topic: Total Knee Arthroplasty (TKA)

In a posterior-stabilized Total Knee Arthroplasty (TKA), the trial components demonstrate a knee that is perfectly balanced and symmetric in full extension but is excessively tight in flexion, causing liftoff and preventing flexion past 80 degrees. The joint line and patellar tracking are acceptable. Which of the following is the most appropriate intraoperative step to balance the knee?

. Use a thinner polyethylene insert
. Resect additional bone from the distal femur
. Release the posterior knee capsule
. Increase the posterior slope of the tibial cut
. Upsize the femoral component

Correct Answer & Explanation

. Increase the posterior slope of the tibial cut

Explanation

When a TKA is balanced in extension but tight in flexion, the flexion gap must be increased without significantly altering the extension gap. Increasing the posterior slope of the tibial cut effectively opens the flexion gap without changing the extension gap. Using a thinner insert or resecting more distal femur would loosen the knee in extension. Upsizing the femoral component would make the flexion space even tighter.

Question 189

Topic: Total Knee Arthroplasty (TKA)

During the final trial phase of a total knee arthroplasty (TKA), the surgeon observes lateral subluxation of the patella during knee flexion. The 'no thumb' test shows the patella popping out of the trochlear groove laterally. Which of the following iatrogenic component malrotations is the most likely cause of this abnormal patellar tracking?

. Internal rotation of the femoral component
. External rotation of the femoral component
. External rotation of the tibial component
. Medialization of the femoral component
. Lateralization of the tibial component

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Lateral patellar maltracking in TKA is often related to malrotation of the components. Internal rotation of the femoral component effectively medializes the trochlear groove relative to the extensor mechanism, increasing the Q-angle and causing the patella to track laterally. Internal rotation of the tibial component (relative to the tibial tubercle) essentially lateralizes the tibial tubercle, also increasing the Q-angle and causing lateral tracking. Therefore, internal rotation of the femoral component is correct.

Question 190

Topic: Total Knee Arthroplasty (TKA)

During a cruciate-retaining total knee arthroplasty (CR-TKA), the surgeon uses spacer blocks to check gap balancing. The extension gap is perfectly balanced, but the knee is significantly too tight in flexion. Which of the following is the most appropriate next step to balance the knee?

. Resect more distal femur
. Downsize the femoral component to resect more posterior condyle
. Decrease the posterior tibial slope
. Upsize the femoral component
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component to resect more posterior condyle

Explanation

If a knee is tight in flexion but balanced in extension, the flexion gap must be increased without affecting the extension gap. Options to specifically increase the flexion gap include downsizing the femoral component (which resects more posterior femoral condylar bone), increasing the posterior tibial slope, or recessing the PCL. Resecting more distal femur would inappropriately increase the extension gap.

Question 191

Topic: Total Knee Arthroplasty (TKA)

During the trial phase of a total knee arthroplasty (TKA) using a gap balancing technique, the surgeon finds that the knee is excessively tight in flexion but perfectly balanced and stable in extension. Which of the following component or bony adjustments is the most appropriate next step?

. Release the posterior cruciate ligament (PCL), increase the posterior slope of the tibial cut, or downsize the femoral component
. Resect an additional 2 millimeters of the distal femur
. Upsize the femoral component to increase the anteroposterior diameter
. Insert a thicker tibial polyethylene insert
. Release the posterior capsule and strip the posterior femur

Correct Answer & Explanation

. Release the posterior cruciate ligament (PCL), increase the posterior slope of the tibial cut, or downsize the femoral component

Explanation

A knee that is tight in flexion but balanced in extension requires addressing the flexion gap without altering the extension gap. Options include decreasing the anteroposterior dimension of the femur (downsizing the femoral component), increasing the posterior tibial slope, or releasing the posterior cruciate ligament (if a CR knee is being used). Resecting more distal femur or releasing the posterior capsule would inappropriately loosen the extension gap.

Question 192

Topic: Total Knee Arthroplasty (TKA)

In total knee arthroplasty, accurately establishing the femoral component rotation is critical for patellofemoral tracking and flexion gap balancing. Which of the following axes is defined by a line connecting the deepest part of the trochlear groove to the center of the intercondylar notch?

. Clinical transepicondylar axis
. Surgical transepicondylar axis
. Whiteside's line
. Posterior condylar axis
. Mechanical axis of the femur

Correct Answer & Explanation

. Whiteside's line

Explanation

Whiteside's line (the anteroposterior axis) is a crucial anatomical landmark used to establish femoral component rotation in TKA. It is defined by drawing a line from the deepest part of the trochlear groove anteriorly to the center of the intercondylar notch posteriorly. The femoral component is typically rotated externally so its posterior condyles are perpendicular to this line.

Question 193

Topic: Total Knee Arthroplasty (TKA)

Which of the following best describes the intended biomechanical advantage of femoral roll-back in a posterior stabilized (PS) total knee arthroplasty?

. It increases the patellofemoral contact forces.
. It anteriorly displaces the axis of rotation to improve extension.
. It improves maximum knee flexion by clearing the posterior femur from the posterior tibia.
. It allows the collateral ligaments to loosen in deep flexion.
. It prevents anterior tibial translation during early flexion.

Correct Answer & Explanation

. It improves maximum knee flexion by clearing the posterior femur from the posterior tibia.

Explanation

Femoral roll-back refers to the posterior translation of the femoral condyles on the tibial plateau during knee flexion. In a posterior stabilized (PS) TKA, the cam-post mechanism enforces this roll-back. The primary biomechanical advantage is that it shifts the contact point posteriorly, delaying impingement of the posterior femoral shaft on the posterior tibia, thereby increasing the maximum achievable knee flexion arc.

Question 194

Topic: Total Knee Arthroplasty (TKA)

During a primary posterior-stabilized total knee arthroplasty, after making the initial measured bone cuts and inserting trial components, the surgeon assesses the gaps. The knee is found to be symmetrically tight in both full extension and 90 degrees of flexion, while the coronal alignment is neutral. Which of the following is the most appropriate next step to achieve balanced gaps?

. Upsize the femoral component
. Resect additional bone from the distal femur
. Resect additional bone from the proximal tibia
. Release the posterior cruciate ligament
. Recut the proximal tibia to increase posterior slope

Correct Answer & Explanation

. Resect additional bone from the proximal tibia

Explanation

Gap balancing in TKA requires understanding which cuts affect which gaps. The proximal tibial cut affects both the flexion and extension gaps equally. If a knee is symmetrically tight in both flexion and extension, the solution is to increase both gaps simultaneously by resecting more bone from the proximal tibia, or by using a thinner polyethylene insert. Resecting more distal femur would only increase the extension gap. Upsizing the femur would tighten the flexion gap.

Question 195

Topic: Total Knee Arthroplasty (TKA)

A 50-year-old recreational runner presents with acute posteromedial knee pain after a minor squatting twisting injury. MRI demonstrates a medial meniscus posterior root tear with 4 mm of meniscal extrusion. If left untreated, this injury rapidly alters knee biomechanics to most closely resemble which of the following?

. An isolated anterior cruciate ligament tear
. A total medial meniscectomy
. A partial medial meniscectomy
. An isolated medial collateral ligament sprain
. A posterior cruciate ligament tear

Correct Answer & Explanation

. A total medial meniscectomy

Explanation

A posterior root tear of the medial meniscus completely disrupts the hoop stresses of the meniscus. Biomechanically, this is equivalent to a total medial meniscectomy and leads to rapid progression of unicompartmental osteoarthritis.

Question 196

Topic: Total Knee Arthroplasty (TKA)

A 3-year-old girl presents with progressive bilateral genu varum and lateral thrust during gait. Radiographs show a sharp varus angulation at the proximal tibial metaphysis with breaking of the medial cortex. Which radiographic measurement is most useful to distinguish infantile Blount disease from physiologic bowing?

. Metaphyseal-diaphyseal angle (Drennan angle)
. Tibiofemoral angle
. Mechanical axis deviation
. Physeal slope angle
. Q angle

Correct Answer & Explanation

. Metaphyseal-diaphyseal angle (Drennan angle)

Explanation

The metaphyseal-diaphyseal angle (Drennan angle) is used to differentiate physiologic bowing from infantile Blount disease. An angle greater than 16 degrees is highly predictive of Blount disease.

Question 197

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA in a patient with a varus deformity, the surgeon assesses the gaps using spacer blocks after making the initial bone cuts. The knee is tight medially in both extension and flexion. What is the most appropriate initial soft tissue release to balance the knee?

. Popliteus tendon
. Iliotibial band
. Deep medial collateral ligament
. Posterior cruciate ligament
. Lateral collateral ligament

Correct Answer & Explanation

. Deep medial collateral ligament

Explanation

When a varus knee is tight medially in both flexion and extension, it indicates a symmetric medial tightness. Release of the deep medial collateral ligament (MCL) off the proximal medial tibia is the most appropriate initial step to balance the gaps.

Question 198

Topic: Total Knee Arthroplasty (TKA)

A 66-year-old man undergoes explantation of an infected TKA and placement of an articulating antibiotic-loaded cement spacer. Six weeks later, his wound is well-healed, and serum ESR and CRP have normalized. Before proceeding with the second-stage reimplantation, what is the most appropriate next step to confirm eradication of the infection?

. Technetium-99m bone scan
. Magnetic resonance imaging (MRI) of the knee
. Synovial fluid aspiration for cell count and culture
. Immediate reimplantation without further diagnostic testing
. Intraoperative frozen section revealing less than 5 PMNs per high-power field

Correct Answer & Explanation

. Synovial fluid aspiration for cell count and culture

Explanation

Prior to a second-stage reimplantation, evaluating the joint for residual infection is critical, even with normalized serum inflammatory markers. Joint aspiration for synovial fluid cell count, culture, and potentially biomarkers is recommended to ensure the infection is eradicated before placing new implants.

Question 199

Topic: Total Knee Arthroplasty (TKA)

A 62-year-old woman complains of a painful catch and an audible pop when actively extending her knee from a flexed position, one year after a primary TKA.

What implant design or technical factor most increases the risk of this specific complication?

. Cruciate-retaining femoral design
. High (proximal) patellar component placement
. A shallow trochlear groove in the femoral component
. Posterior-stabilized design with a sharp anterior aspect of the intercondylar box
. Oversizing the tibial component

Correct Answer & Explanation

. Posterior-stabilized design with a sharp anterior aspect of the intercondylar box

Explanation

This presentation is classic for patellar clunk syndrome, caused by a fibrotic nodule forming at the superior pole of the patella. It is most commonly associated with posterior-stabilized (PS) designs due to the nodule catching in the intercondylar box during extension.

Question 200

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA using a measured resection technique, the extension gap is symmetric and perfectly balanced, but the flexion gap is unacceptably tight. What is the most appropriate surgical step to correct this mismatch?

. Resect more distal femur
. Release the posterior capsule
. Downsize the femoral component and augment the posterior condyles
. Downsize the femoral component to resect more posterior femoral condyle
. Use a thinner polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component to resect more posterior femoral condyle

Explanation

A tight flexion gap with a balanced extension gap implies the anteroposterior dimension of the femoral component is too large. Downsizing the femoral component removes more posterior bone, which opens the flexion gap without altering the extension gap.

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