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Total Knee Arthroplasty (TKA) MCQs

Practice Set 20 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 381

Topic: Total Knee Arthroplasty (TKA)

A patient with a posterior-stabilized (PS) TKA develops restricted mid-flexion and a sense of 'tightness' despite adequate gap balancing. Postoperative radiographs reveal that the joint line has been significantly elevated. What is the primary kinematic consequence of joint line elevation in a PS TKA?

. Early cam-post engagement
. Late cam-post engagement
. Paradoxical anterior rollback
. Patella baja with secondary extension deficit
. Excessive posterior femoral rollback in deep flexion

Correct Answer & Explanation

. Early cam-post engagement

Explanation

Elevating the joint line in a PS knee moves the tibial post proximally relative to the femoral cam, causing early cam-post engagement. This restricts flexion and increases the risk of post wear or fracture.

Question 382

Topic: Total Knee Arthroplasty (TKA)

During gap balancing in a primary TKA, the surgeon notes that the flexion gap is symmetrically loose by 4 mm, while the extension gap is perfectly balanced. Which of the following adjustments is most appropriate to balance the knee?

. Increase the thickness of the tibial polyethylene insert
. Downsize the femoral component and augment the posterior condyles
. Upsize the femoral component to increase the anteroposterior dimension
. Translate the femoral component proximally
. Recut the distal femur to remove more bone

Correct Answer & Explanation

. Upsize the femoral component to increase the anteroposterior dimension

Explanation

A knee that is loose in flexion but balanced in extension requires an isolated decrease in the flexion gap. Upsizing the femoral component increases its AP dimension, filling the flexion gap without affecting the distal femoral extension gap.

Question 383

Topic: Total Knee Arthroplasty (TKA)

A patient sustains an acute extensor mechanism rupture (complete patellar tendon avulsion) 3 weeks after a primary TKA. Due to poor tissue quality, a primary repair is augmented. Among the following options, which reconstruction technique provides the most reliable long-term clinical outcome?

. Primary repair with cerclage wire augmentation
. Reconstruction using synthetic mesh or an extensor mechanism allograft
. Gastrocnemius rotational flap
. Tibial tubercle osteotomy with proximal advancement
. Patellectomy and V-Y quadricepsplasty

Correct Answer & Explanation

. Reconstruction using synthetic mesh or an extensor mechanism allograft

Explanation

Primary repair of extensor mechanism ruptures post-TKA has an extremely high failure rate. Synthetic mesh (e.g., Marlex) or complete extensor mechanism allograft reconstruction are the preferred techniques with the most durable outcomes.

Question 384

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty (TKA), the surgeon evaluates patellar tracking after trial placement. The patella subluxates laterally during flexion despite a normal Q-angle preoperatively. Which of the following technical errors is the most likely cause of this abnormal patellar kinematics?

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

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral component shifts the trochlear groove medially, effectively increasing the Q-angle and causing lateral patellar maltracking. External rotation of the femoral and tibial components generally improves patellar tracking.

Question 385

Topic: Total Knee Arthroplasty (TKA)

While trialing components during a primary TKA, the surgeon notes that the knee is symmetric and stable at 90 degrees of flexion, but it is symmetric and excessively loose in full extension. Which of the following intraoperative adjustments is the best step to balance the knee?

. Increase the thickness of the polyethylene insert
. Upsize the femoral component
. Downsize the femoral component
. Use distal femoral augments
. Release the posterior capsule

Correct Answer & Explanation

. Use distal femoral augments

Explanation

A knee that is stable in flexion but loose in extension indicates an isolated extension gap laxity. Using distal femoral augments (or reducing the distal femoral resection) tightens the extension gap without affecting the flexion gap.

Question 386

Topic: Total Knee Arthroplasty (TKA)

A patient presents with anterior knee pain and a palpable, audible catch as the knee extends from 40 degrees of flexion to full extension, one year after a primary TKA. This complication (patellar clunk syndrome) is most classically associated with which type of implant design?

. Cruciate-retaining (CR)
. Mobile-bearing
. Posterior-stabilized (PS)
. Medial pivot
. Hinged knee prosthesis

Correct Answer & Explanation

. Posterior-stabilized (PS)

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized (PS) knee designs. A fibrotic nodule forms at the superior pole of the patella and catches in the intercondylar box of the femoral component during knee extension.

Question 387

Topic: Total Knee Arthroplasty (TKA)

A surgeon is performing a TKA on a patient with a severe fixed valgus deformity. A lateral parapatellar approach is utilized. During gap balancing, the lateral extension gap remains excessively tight. Which of the following lateral structures is typically released first to balance the extension gap in a valgus knee?

. Popliteus tendon
. Lateral collateral ligament (LCL)
. Biceps femoris
. Iliotibial (IT) band
. Lateral head of the gastrocnemius

Correct Answer & Explanation

. Iliotibial (IT) band

Explanation

In a severe valgus knee, the iliotibial (IT) band is the primary tether in extension. It is typically the first structure selectively released or pie-crusted off Gerdy's tubercle to correct a tight lateral extension gap.

Question 388

Topic: Total Knee Arthroplasty (TKA)

A patient complains of a sensation of the knee "giving way" when descending stairs 6 months after a TKA. Clinical examination reveals the knee is perfectly stable to varus and valgus stress in full extension, but demonstrates significant laxity in varus and valgus at 90 degrees of flexion. Which of the following surgical errors is the most likely cause?

. Excessive distal femoral resection
. Undersizing the anteroposterior (AP) dimension of the femoral component
. Oversizing the anteroposterior (AP) dimension of the femoral component
. Using an excessively thick polyethylene insert
. Inadequate posterior tibial slope

Correct Answer & Explanation

. Undersizing the anteroposterior (AP) dimension of the femoral component

Explanation

Instability isolated to flexion is known as flexion instability. It is classically caused by undersizing the AP dimension of the femoral component, which fails to adequately tension the collateral ligaments when the knee is flexed.

Question 389

Topic: Total Knee Arthroplasty (TKA)

A patient with a chronically infected TKA caused by a sensitive Staphylococcus aureus is scheduled for a two-stage revision. What is the standard duration of antibiotic-free interval recommended before reimplantation to confirm eradication?

. Less than 72 hours.
. 1 to 2 weeks.
. 4 weeks.
. 6 weeks.
. No antibiotic-free interval is necessary.

Correct Answer & Explanation

. 1 to 2 weeks.

Explanation

To accurately assess for infection eradication during a two-stage revision, an antibiotic-free interval of at least 1 to 2 weeks (often 2 weeks is preferred) is recommended before performing repeat aspirations for culture. This 'antibiotic holiday' allows any remaining bacteria to regain metabolic activity, thus increasing the sensitivity of cultures and minimizing false negatives caused by antibiotic suppression. Less than 72 hours is too short, and longer periods may increase the risk of re-infection or spacer complications.

Question 390

Topic: Total Knee Arthroplasty (TKA)

For patients with an infected TKA who undergo a two-stage revision, what is generally the most important factor for maximizing patient satisfaction and functional outcomes after reimplantation?

. Use of the latest generation of prosthetic components.
. Early weight-bearing on the cement spacer.
. Aggressive physical therapy and rehabilitation to restore motion and strength.
. Prolonged systemic antibiotic therapy post-reimplantation.
. Strict adherence to a low-impact lifestyle.

Correct Answer & Explanation

. Aggressive physical therapy and rehabilitation to restore motion and strength.

Explanation

Aggressive physical therapy and rehabilitation to restore motion and strength are paramount for maximizing patient satisfaction and functional outcomes after reimplantation. While infection eradication is the primary goal, functional recovery depends heavily on regaining range of motion, strength, and confidence in the limb. Spacer choice (articulating), early mobilization, and dedicated rehab are critical. The latest components or prolonged antibiotics alone do not guarantee good function, and a low-impact lifestyle may be necessary but doesn't drive satisfaction as much as regained function.

Question 391

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old male undergoes TKA. On post-operative day 5, he develops a fever of 39.5°C and severe pain. The wound is erythematous and draining purulent fluid. What is the most likely pathogen?

. Staphylococcus epidermidis.
. Cutibacterium acnes.
. Staphylococcus aureus.
. Candida albicans.
. Escherichia coli.

Correct Answer & Explanation

. Staphylococcus aureus.

Explanation

An acute, virulent infection developing within days to a week post-operatively, presenting with high fever, severe pain, and purulent drainage, is most characteristic of Staphylococcus aureus. S. aureus is a highly virulent pathogen often associated with acute, rapidly progressing infections. S. epidermidis and Cutibacterium acnes typically cause more indolent, late-onset infections. Candida and E. coli are less common but can cause acute infections, though S. aureus is the most likely in this classic scenario.

Question 392

Topic: Total Knee Arthroplasty (TKA)

A patient presents with a feeling of instability and giving way in full extension after TKA. Radiographs demonstrate well-fixed components with appropriate sizing. Which sagittal plane malalignment is the most likely culprit?

. Excessive tibial posterior slope
. Insufficient tibial posterior slope
. Femoral component placed in excessive flexion
. Tibial component placed in excessive extension
. Patellar baja

Correct Answer & Explanation

. Excessive tibial posterior slope

Explanation

Excessive tibial posterior slope can lead to an extensor lag and instability in extension. It creates a relatively 'loose' extension gap and a 'tight' flexion gap, pushing the femur posteriorly on the tibia in extension and potentially causing hyperextension or feeling of giving way. Insufficient tibial posterior slope typically leads to a tight flexion gap and difficulty with flexion. Femoral component placed in excessive flexion causes a flexion contracture. Tibial component placed in excessive extension is an unusual term, usually referred to as insufficient posterior slope. Patellar baja is related to patellofemoral mechanics, not directly extension instability.

Question 393

Topic: Total Knee Arthroplasty (TKA)

What is the primary consequence of significant internal rotation of the tibial component in a TKA?

. Medial patellofemoral impingement
. Increased medial collateral ligament tension in flexion
. Altered flexion gap kinetics leading to lateral instability in flexion
. Reduced range of motion in extension
. Increased risk of deep vein thrombosis

Correct Answer & Explanation

. Altered flexion gap kinetics leading to lateral instability in flexion

Explanation

Significant internal rotation of the tibial component creates an asymmetrical flexion gap, often leading to a relatively tighter medial compartment and a looser lateral compartment during knee flexion. This can manifest as lateral instability in flexion, subluxation, or even impingement in some cases. It can also contribute to patellofemoral tracking issues but primarily affects the tibiofemoral kinematics in flexion. Medial patellofemoral impingement is less common, and ligament tension changes are usually complex rather than simply increased MCL tension.

Question 394

Topic: Total Knee Arthroplasty (TKA)

For accurate assessment of overall mechanical axis post-TKA, which imaging study is considered the gold standard?

. Anterior-posterior (AP) view of the knee
. Lateral view of the knee
. Merchant view of the patella
. Full-length standing anteroposterior (AP) radiograph of both lower extremities
. CT scan of the knee

Correct Answer & Explanation

. Full-length standing anteroposterior (AP) radiograph of both lower extremities

Explanation

A full-length standing anteroposterior (AP) radiograph of both lower extremities (often called a 'long leg alignment view') is the gold standard for assessing the overall mechanical axis of the lower limb. This view allows measurement from the center of the femoral head to the center of the ankle, passing through the knee, providing a comprehensive assessment of the coronal alignment and load transmission. Other views are useful for specific details but don't provide the complete mechanical axis picture.

Question 395

Topic: Total Knee Arthroplasty (TKA)

A patient experiences a medial collateral ligament (MCL) tear during a TKA. Which femoral component rotational malposition is most likely to predispose to this complication if the flexion gap is aggressively balanced?

. Excessive femoral external rotation
. Insufficient femoral external rotation (internal rotation)
. Femoral component varus placement
. Femoral component valgus placement
. Femoral component in excessive flexion

Correct Answer & Explanation

. Insufficient femoral external rotation (internal rotation)

Explanation

Insufficient femoral external rotation (i.e., internal rotation) during TKA can lead to a tight medial flexion gap. If the surgeon attempts to balance this aggressively with releases, or if significant force is applied during reduction or range of motion, it can overstress and potentially tear the MCL. Excessive femoral external rotation would make the medial flexion gap loose. Coronal alignment (varus/valgus) and sagittal alignment (flexion) primarily affect different aspects of stability and range of motion.

Question 396

Topic: Total Knee Arthroplasty (TKA)

Which of the following is considered the most common cause of patellofemoral complications after TKA?

. Tibial component varus malalignment
. Excessive tibial posterior slope
. Rotational malalignment of the femoral or tibial components
. Component undersizing
. Posterior cruciate ligament insufficiency

Correct Answer & Explanation

. Rotational malalignment of the femoral or tibial components

Explanation

Rotational malalignment of either the femoral or tibial components is the most common cause of patellofemoral complications (e.g., maltracking, anterior knee pain, patellar tilt) after TKA. Incorrect rotation can alter the patellofemoral kinematics, leading to lateralization or medialization of the patella within the trochlear groove. Other options have different primary consequences.

Question 397

Topic: Total Knee Arthroplasty (TKA)

When performing a measured resection technique, what is the desired amount of external rotation for the femoral component relative to the posterior condylar line in most valgus knees?

. 0 degrees (parallel)
. 3 degrees internal rotation
. 3-5 degrees external rotation
. 7-10 degrees external rotation
. 10-15 degrees internal rotation

Correct Answer & Explanation

. 3-5 degrees external rotation

Explanation

In a measured resection technique, the femoral component is typically placed in 3-5 degrees of external rotation relative to the posterior condylar line to avoid internal rotation of the femoral component and to align with the transepicondylar axis. This compensates for the natural internal rotation of the posterior condyles relative to the surgical epicondylar axis. In severe valgus knees with hypoplastic lateral condyles, using the posterior condylar line may still result in internal rotation, and the TEA or Whiteside's line should be considered the primary reference.

Question 398

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old patient presents with recurrent knee effusions and a grinding sensation 2 years after TKA. Radiographs show no obvious loosening or infection. On examination, there's a palpable clunk during knee flexion and extension. A CT scan is obtained and reveals significant component impingement. Which type of malalignment is most likely causing this issue?

. Excessive tibial posterior slope
. Tibial component undersizing
. Femoral component oversizing (anterior-posterior dimension)
. Patellar component tilt
. Insufficient femoral external rotation

Correct Answer & Explanation

. Femoral component oversizing (anterior-posterior dimension)

Explanation

Femoral component oversizing, particularly in the anterior-posterior dimension, can lead to impingement of the posterior soft tissues (e.g., posterior capsule) during flexion or the extensor mechanism in extension, causing a clunk, grinding, stiffness, and recurrent effusions. Excessive tibial posterior slope usually causes laxity in extension. Tibial component undersizing can cause subsidence. Patellar component tilt primarily causes patellofemoral pain. Insufficient femoral external rotation leads to patellofemoral maltracking or medial compartment tightness.

Question 399

Topic: Total Knee Arthroplasty (TKA)

Which surgical technique specifically aims to avoid rotational malalignment of the femoral component by referencing the functional flexion-extension axis?

. Measured resection technique
. Gap balancing technique
. Navigation-assisted surgery
. Conventional intramedullary guides
. Extramedullary tibial guides

Correct Answer & Explanation

. Navigation-assisted surgery

Explanation

Navigation-assisted surgery and robotics are designed to precisely control component alignment, including rotational alignment, by referencing anatomical landmarks and often the functional flexion-extension axis. While both measured resection and gap balancing techniques aim for good alignment, navigation provides real-time feedback and often uses a registration process to define axes more accurately, helping to avoid rotational malalignment based on the functional axis. Conventional guides rely on external or internal landmarks that can be variable or affected by deformity.

Question 400

Topic: Total Knee Arthroplasty (TKA)

What is the most accurate imaging modality for assessing subtle rotational malalignment of the femoral and tibial components after TKA?

. Standard knee AP and lateral radiographs
. Long leg alignment radiograph
. Computed Tomography (CT) scan
. Magnetic Resonance Imaging (MRI)
. Bone scintigraphy

Correct Answer & Explanation

. Computed Tomography (CT) scan

Explanation

Computed Tomography (CT) scan is considered the most accurate imaging modality for assessing subtle rotational malalignment of both femoral and tibial components post-TKA. It allows for precise measurement of component rotation relative to anatomical landmarks (e.g., transepicondylar axis, tibial tubercle). Standard radiographs and long leg views are less effective for detailed rotational assessment. MRI can assess soft tissues well but is not superior to CT for bone-implant rotational measurements. Bone scintigraphy assesses metabolic activity, not alignment.

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