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Total Knee Arthroplasty (TKA) MCQs

Practice Set 21 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 401

Topic: Total Knee Arthroplasty (TKA)

A patient reports a 'giving way' sensation and recurrent effusions after TKA, particularly when pivoting. Clinical examination reveals mild laxity in flexion. What is a common cause of this type of instability?

. Excessive femoral component external rotation
. Excessive tibial posterior slope
. Inadequate soft tissue balancing of the flexion gap
. Femoral component undersizing in the A-P dimension
. All of the above

Correct Answer & Explanation

. All of the above

Explanation

All listed options can contribute to instability in flexion. Excessive femoral component external rotation can lead to MCL laxity. Excessive tibial posterior slope creates a relatively loose flexion gap. Inadequate soft tissue balancing (e.g., insufficient release of a tight side or excessive release of a loose side) directly causes gap asymmetry and instability. Femoral component undersizing in the A-P dimension can also lead to a loose flexion gap. Therefore, 'All of the above' is the best answer as these factors often combine or are isolated causes of flexion instability.

Question 402

Topic: Total Knee Arthroplasty (TKA)

What effect does persistent patella alta after TKA typically have on patellofemoral mechanics?

. Increased patellofemoral contact pressure in early flexion
. Reduced patellofemoral contact pressure in early flexion
. Increased risk of patellar clunk syndrome
. Improved patellar tracking
. Reduced risk of anterior knee pain

Correct Answer & Explanation

. Reduced patellofemoral contact pressure in early flexion

Explanation

Patella alta (high-riding patella) after TKA typically leads to reduced patellofemoral contact pressure in early flexion because the patella engages the femoral trochlear groove later. This can cause instability, a feeling of 'giving way', or difficulty initiating flexion. Patellar baja (low-riding patella) is associated with increased contact pressure, crepitus, and a higher risk of patellar clunk syndrome. Improved tracking and reduced anterior knee pain are unlikely with patella alta.

Question 403

Topic: Total Knee Arthroplasty (TKA)

Which of the following is the most appropriate strategy to correct a tight extension gap and a loose flexion gap during TKA?

. Increase femoral component size
. Increase tibial polyethylene insert thickness
. Re-resect more distal femur
. Re-resect more proximal tibia
. Decrease tibial posterior slope

Correct Answer & Explanation

. Re-resect more distal femur

Explanation

A tight extension gap suggests insufficient distal femoral resection, while a loose flexion gap often indicates over-resection of the posterior femoral condyles or an overall loose flexion space. To address a tight extension gap, re-resecting more distal femur is appropriate. This will also slightly loosen the flexion gap, which is already loose, so further consideration of flexion gap balancing would be needed. Increasing femoral component size would tighten both gaps. Increasing poly thickness would tighten both gaps. Re-resecting proximal tibia would further loosen the extension gap. Decreasing tibial posterior slope would tighten the flexion gap, but wouldn't directly address the tight extension gap.

Question 404

Topic: Total Knee Arthroplasty (TKA)

A TKA patient complains of a clunk and anterior knee pain. During surgical exploration, a fibrous nodule is found superior to the patellar component, within the quadriceps tendon. This is characteristic of:

. Patella alta
. Patella baja
. Patellar clunk syndrome
. Tibial component internal rotation
. Femoral component external rotation

Correct Answer & Explanation

. Patellar clunk syndrome

Explanation

This clinical description (clunk, anterior knee pain, fibrous nodule superior to the patellar component in the quadriceps tendon) is characteristic of 'patellar clunk syndrome.' It is more commonly associated with patellar baja or femoral component design issues that allow impingement of the suprapatellar pouch. Patella alta or rotational malalignment would typically present with different patellofemoral tracking issues rather than a specific fibrous nodule.

Question 405

Topic: Total Knee Arthroplasty (TKA)

When balancing the extension gap in a TKA, what is the ideal soft tissue tension?

. Visibly tight, no space can be created between components
. Just able to insert a thin feeler gauge (e.g., 2mm)
. Evenly balanced and stable, but not overtly tight or loose, allowing for a 1-2mm distraction with firm manual stress
. Loose enough to easily distract the joint by 5mm
. Variable, depending on patient's activity level

Correct Answer & Explanation

. Evenly balanced and stable, but not overtly tight or loose, allowing for a 1-2mm distraction with firm manual stress

Explanation

The ideal soft tissue tension in the extension gap should be evenly balanced and stable, but not overtly tight or loose. It should allow for 1-2mm of distraction with firm manual stress. This provides stability without restricting motion or causing impingement. Visibly tight or loose gaps are indicative of malalignment or inadequate balancing. The goal is to achieve a rectangular gap, equal to the flexion gap.

Question 406

Topic: Total Knee Arthroplasty (TKA)

A patient presents with a TKA reporting that their knee feels 'too tight' and they cannot fully flex. Radiographs show a well-aligned femoral component but a tibial component with an unusually steep posterior slope. What is the likely consequence of this tibial slope?

. Flexion contracture
. Hyperextension and anterior knee pain
. Anterior impingement and difficulty with terminal extension
. Loose flexion gap and posterior instability
. Increased patellofemoral contact forces

Correct Answer & Explanation

. Loose flexion gap and posterior instability

Explanation

An unusually steep (excessive) posterior slope of the tibial component creates a relatively loose flexion gap and can lead to posterior instability, particularly during flexion. It also predisposes to hyperextension. A flexion contracture is associated withinsufficientposterior slope or femoral component flexion. Anterior impingement is usually with insufficient slope. Increased patellofemoral forces are not directly caused by tibial slope, though instability can indirectly affect the patella.

Question 407

Topic: Total Knee Arthroplasty (TKA)

What is the 'kinematic alignment' philosophy in TKA aiming to achieve regarding component placement?

. To restore a neutral mechanical axis of 0 degrees
. To align components such that the joint line is parallel to the floor in standing
. To reproduce the patient's pre-arthritic constitutional knee alignment
. To achieve an ideal 3 degrees of valgus for the femoral component
. To always use a measured resection technique

Correct Answer & Explanation

. To reproduce the patient's pre-arthritic constitutional knee alignment

Explanation

Kinematic alignment (KA) in TKA aims to reproduce the patient's pre-arthritic constitutional knee alignment and the native joint kinematics. This often results in a slight varus or valgus overall alignment, rather than a forced neutral mechanical axis. It contrasts with mechanical alignment (MA) which strives for a neutral mechanical axis. The goal is to avoid overstuffing or understuffing the joint based on individual anatomy.

Question 408

Topic: Total Knee Arthroplasty (TKA)

In a TKA, a common cause of recurrent lateral patellar subluxation or dislocation is:

. Medial patellar component placement
. External rotation of the tibial component
. Internal rotation of the femoral component
. Insufficient posterior slope of the tibial component
. Valgus malalignment of the overall mechanical axis

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral component is a common cause of lateral patellar subluxation or dislocation. It effectively lateralizes the trochlear groove relative to the patella, predisposing to tracking issues. External rotation of the tibial component could also contribute but femoral rotational malalignment is a more potent factor. Medial patellar placement would tend to stabilize. Insufficient posterior slope and overall valgus malalignment are less directly linked to patellar tracking.

Question 409

Topic: Total Knee Arthroplasty (TKA)

A TKA patient develops chronic anterior knee pain and a feeling of 'catch' or 'clunk' in mid-flexion. Radiographs are unremarkable. Which component malalignment would most likely be implicated in anterior impingement of the patella or extensor mechanism in flexion?

. Femoral component undersizing
. Excessive anterior position of the femoral component (e.g., inadequate anterior femoral cut)
. Excessive posterior slope of the tibial component
. Tibial component internal rotation
. Patellar component varus tilt

Correct Answer & Explanation

. Excessive anterior position of the femoral component (e.g., inadequate anterior femoral cut)

Explanation

Excessive anterior positioning of the femoral component (resulting from inadequate resection of the anterior femur or an oversized component) can lead to anterior impingement of the patella or extensor mechanism, causing a clunk or catch in mid-flexion. This effectively narrows the patellofemoral space. Undersizing might cause instability, not impingement. Excessive posterior tibial slope would cause posterior instability. Rotational or tilt issues lead to tracking problems, not typically anterior impingement in mid-flexion in this manner.

Question 410

Topic: Total Knee Arthroplasty (TKA)

When assessing the sagittal alignment of the femoral component on a true lateral radiograph, which line should be parallel to the anterior femoral cortex?

. Posterior femoral condylar line
. Anterior femoral condylar line (of the component)
. Transepicondylar axis
. Whiteside's line
. Mechanical axis of the femur

Correct Answer & Explanation

. Anterior femoral condylar line (of the component)

Explanation

On a true lateral radiograph, the anterior femoral condylar line of the component should be parallel to the anterior femoral cortex. This indicates proper sagittal positioning of the femoral component, avoiding notching or anterior impingement. The posterior condylar line indicates flexion/extension relative to the shaft. The other options are for rotational or overall mechanical alignment.

Question 411

Topic: Total Knee Arthroplasty (TKA)

What is the primary technical goal of using a 'gap balancing' technique in TKA?

. To ensure bone cuts are perpendicular to the mechanical axis
. To achieve equal and rectangular flexion and extension gaps
. To restore the constitutional alignment of the patient's knee
. To minimize blood loss during surgery
. To avoid notching of the femoral cortex

Correct Answer & Explanation

. To achieve equal and rectangular flexion and extension gaps

Explanation

The primary technical goal of the 'gap balancing' technique in TKA is to achieve equal and rectangular flexion and extension gaps. This is done by assessing the soft tissue tension in both flexion and extension and making bone resections and soft tissue releases to create balanced, symmetrical gaps of the same dimension. This ensures stability throughout the range of motion. While mechanical axis restoration is a goal, gap balancing focuses on the soft tissue envelopes.

Question 412

Topic: Total Knee Arthroplasty (TKA)

A patient with a TKA reports chronic posterior knee pain and a feeling of instability during staircase ascent. A lateral radiograph shows slight posterior subluxation of the femoral component on the tibial tray. Which malalignment is most likely?

. Excessive anterior slope of the tibial component (reversed slope)
. Insufficient posterior slope of the tibial component
. Excessive posterior slope of the tibial component
. Femoral component undersizing
. Internal rotation of the tibial component

Correct Answer & Explanation

. Excessive posterior slope of the tibial component

Explanation

Excessive posterior slope of the tibial component creates a relatively loose flexion gap and can lead to posterior subluxation of the femoral component on the tibial tray, particularly during activities like staircase ascent which involve high flexion and posterior shear forces. It effectively allows the femur to slide posteriorly. Insufficient posterior slope would cause tightness in flexion. Femoral undersizing might cause instability, but posterior subluxation is highly indicative of excessive posterior slope.

Question 413

Topic: Total Knee Arthroplasty (TKA)

When templating for TKA, what is the most important measurement to ensure proper restoration of limb length and joint line?

. Preoperative knee flexion range of motion
. Preoperative patellar height
. Distal femoral resection amount relative to epicondylar axis
. Overall mechanical axis deviation
. Preoperative distal femoral length and proximal tibial length relative to fixed landmarks

Correct Answer & Explanation

. Preoperative distal femoral length and proximal tibial length relative to fixed landmarks

Explanation

To ensure proper restoration of limb length and joint line, it is crucial to measure the preoperative distal femoral length and proximal tibial length relative to fixed anatomical landmarks (e.g., femoral head, ankle joint, fibular head). This helps guide bone resections to avoid either lengthening or shortening the limb significantly and to maintain the natural joint line, preventing patella baja or alta. Other options are important but not directly forbothlimb length and joint line restoration.

Question 414

Topic: Total Knee Arthroplasty (TKA)

When performing TKA, the anterior femoral cortex is accidentally 'notched' during distal femoral resection. What malalignment or surgical error predisposes to this?

. Femoral component undersizing
. Excessive posterior slope of the femoral component
. Using an overly anterior entry point for the intramedullary guide rod
. Insufficient distal femoral resection
. Excessive external rotation of the femoral component

Correct Answer & Explanation

. Using an overly anterior entry point for the intramedullary guide rod

Explanation

Notching of the anterior femoral cortex occurs when the intramedullary guide rod for distal femoral resection is placed with an overly anterior entry point, leading to an oblique cut that compromises the anterior cortex. This can predispose to periprosthetic fracture. It is not directly related to femoral component sizing, slope, or rotation, but rather to the distal femoral cutting block's positioning. Insufficient distal femoral resection would lead to a tight extension gap, not notching.

Question 415

Topic: Total Knee Arthroplasty (TKA)

Which intraoperative assessment confirms adequate rotational alignment of the tibial component relative to the femoral component in flexion?

. The tibial component is parallel to the mechanical axis of the tibia on a long leg view
. The patella tracks centrally in the femoral trochlea during flexion-extension
. The femoral component is 3-5 degrees externally rotated to the posterior condyles
. The medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block
. The tibial component has a 3-degree posterior slope

Correct Answer & Explanation

. The medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block

Explanation

Adequate rotational alignment of the tibial component relative to the femoral component, especially in flexion, is confirmed when the medial and lateral flexion gaps are equal and rectangular when evaluated with a spacer block. This indicates that the tibiofemoral articulation is balanced and symmetrical in the rotational plane. While central patellar tracking is a good sign, the gap assessment is a direct measure of tibiofemoral rotation. Other options describe different aspects of alignment.

Question 416

Topic: Total Knee Arthroplasty (TKA)

What is the potential consequence of restoring the joint line too proximally in TKA?

. Patella alta
. Patella baja
. Increased risk of extensor mechanism impingement
. Increased range of motion
. Reduced risk of quadriceps weakness

Correct Answer & Explanation

. Patella baja

Explanation

Restoring the joint line too proximally (i.e., making the distal femoral cut and/or proximal tibial cut more proximally than the native joint line) can lead to patella baja (low-riding patella). This shortens the patellar tendon moment arm, increases patellofemoral contact forces, can cause anterior knee pain, crepitus, and potentially patellar clunk syndrome. Patella alta is due to a more distally restored joint line.

Question 417

Topic: Total Knee Arthroplasty (TKA)

What is a characteristic symptom of symptomatic patella baja after TKA?

. Lateral patellar subluxation and a 'J' sign
. Difficulty initiating knee flexion and increased patellofemoral pressure
. Hyperextension and instability
. Posterior knee pain and clunking in deep flexion
. Effusion without pain

Correct Answer & Explanation

. Difficulty initiating knee flexion and increased patellofemoral pressure

Explanation

Symptomatic patella baja (low-riding patella) after TKA typically manifests as difficulty initiating knee flexion, increased patellofemoral contact pressure, anterior knee pain, crepitus, and sometimes patellar clunk syndrome. It can also lead to a functional shortening of the quadriceps moment arm. Lateral patellar subluxation and a 'J' sign are more indicative of patella alta or rotational malalignment. Hyperextension is related to tibial slope. Posterior knee pain and clunking in deep flexion often relate to posterior impingement or loose bodies.

Question 418

Topic: Total Knee Arthroplasty (TKA)

What is the clinical significance of a persistent 'quadriceps lag' after TKA, despite good surgical alignment and rehabilitation?

. Suggests patella alta
. Suggests patella baja
. Indicates a potentially overlooked infection
. May be due to persistent flexion contracture or extensor mechanism weakness
. Points to excessive femoral component external rotation

Correct Answer & Explanation

. May be due to persistent flexion contracture or extensor mechanism weakness

Explanation

A persistent quadriceps lag (inability to actively extend the knee fully, even if passive extension is full) after TKA, when alignment is otherwise good, often indicates persistent extensor mechanism weakness (e.g., due to preoperative atrophy, pain, or nerve injury) or a subtle, persistent flexion contracture that is difficult to overcome. It is not directly indicative of patella alta or baja (though these can cause extensor dysfunction), nor an infection or specific rotational error in this general context.

Question 419

Topic: Total Knee Arthroplasty (TKA)

When using a computer navigation system for TKA, what is the primary benefit regarding component malalignment prevention?

. Eliminates the need for soft tissue releases
. Automatically compensates for severe bone deformities without manual input
. Provides real-time, objective data on bone cuts and component orientation, minimizing manual measurement errors
. Reduces surgical time significantly
. Guarantees a perfectly sterile surgical field

Correct Answer & Explanation

. Provides real-time, objective data on bone cuts and component orientation, minimizing manual measurement errors

Explanation

The primary benefit of computer navigation systems in TKA regarding component malalignment prevention is that they provide real-time, objective data on bone cuts and component orientation. This minimizes manual measurement errors and allows the surgeon to verify and adjust alignment precisely, especially in complex cases, ultimately leading to more accurate component placement. It does not eliminate the need for releases, isn't fully automatic, often increases surgical time, and doesn't guarantee sterility.

Question 420

Topic: Total Knee Arthroplasty (TKA)

What is the most accurate method to assess the patellar height after TKA?

. Insall-Salvati ratio
. Blackburne-Peel ratio
. Caton-Deschamps index
. Lateral knee radiograph
. All of the above indices on a lateral knee radiograph

Correct Answer & Explanation

. All of the above indices on a lateral knee radiograph

Explanation

All listed indices (Insall-Salvati, Blackburne-Peel, Caton-Deschamps) are commonly used to assess patellar height on a lateral knee radiograph. The choice of index may depend on surgeon preference or specific clinical scenarios, but a true lateral radiograph is essential for applying these measurements accurately. Therefore, 'All of the above indices on a lateral knee radiograph' is the most complete answer.

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