Menu

3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 295 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 5881

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following organisms is particularly challenging to culture in standard laboratory settings and may require extended incubation times (e.g., 10-14 days) for detection?

. Staphylococcus aureus.
. Streptococcus pyogenes.
. Pseudomonas aeruginosa.
. Cutibacterium acnes.
. Escherichia coli.

Correct Answer & Explanation

. Cutibacterium acnes.

Explanation

Cutibacterium acnes (formerly Propionibacterium acnes) is a slow-growing, fastidious anaerobic organism that is a common cause of low-grade PJI, particularly in the shoulder, but also in the knee. Its detection often requires extended incubation times (10-14 days or longer) for cultures to become positive. The other listed organisms are typically identified within standard incubation periods (2-5 days).

Question 5882

Topic: 3. Adult Reconstruction (Hip & Knee)

A 68-year-old female presents with persistent anterior knee pain and crepitus 6 months after a total knee arthroplasty. Clinical examination reveals difficulty with terminal knee extension and a positive 'J' sign during flexion. Radiographs show a well-fixed patellar component without obvious tilt. Which of the following component malalignments is the most likely cause?

. Femoral component external rotation
. Tibial component excessive valgus
. Patellar component medialization
. Femoral component internal rotation
. Tibial component posterior slope

Correct Answer & Explanation

. Femoral component internal rotation

Explanation

Persistent anterior knee pain with a positive 'J' sign post-TKA is highly suggestive of patellofemoral maltracking, often caused by internal rotation of the femoral component. This effectively lateralizes the patella in relation to the trochlear groove, increasing lateral patellar facet pressure and causing symptoms. External rotation of the femoral component would tend to medialize the patella. Tibial valgus or posterior slope would not directly cause a 'J' sign. Patellar component medialization would generally improve tracking, not worsen it.

Question 5883

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes a primary total knee arthroplasty. Postoperatively, they complain of a persistent flexion contracture of 15 degrees, despite aggressive physical therapy. Radiographs show adequately sized components. Which of the following intraoperative technical errors is the most probable cause?

. Excessive tibial posterior slope
. Insufficient posterior femoral condylar resection
. Over-resection of the anterior femoral condyle
. Femoral component placed in excessive flexion
. Tibial component placed in excessive valgus

Correct Answer & Explanation

. Femoral component placed in excessive flexion

Explanation

A persistent flexion contracture post-TKA is frequently caused by placing the femoral component in excessive flexion. This elevates the anterior femoral condyles relative to the mechanical axis, impinging on the extensor mechanism in extension. Insufficient posterior femoral condylar resection would lead to a tight flexion gap, not necessarily a contracture in extension. Over-resection of the anterior femoral condyle could cause patella alta or patellar instability. Excessive tibial posterior slope would cause laxity in flexion and potentially hyperextension. Excessive tibial valgus primarily affects coronal alignment and stability.

Question 5884

Topic: 3. Adult Reconstruction (Hip & Knee)

A 72-year-old male develops early aseptic loosening of his tibial component 3 years after a TKA for varus osteoarthritis. What is the most common coronal plane malalignment associated with early aseptic loosening of the tibial component?

. Tibial component placed in 5 degrees of valgus
. Tibial component placed in 3 degrees of varus
. Femoral component placed in 7 degrees of valgus
. Femoral component placed in 3 degrees of flexion
. Overall mechanical axis restored to 0 degrees

Correct Answer & Explanation

. Tibial component placed in 3 degrees of varus

Explanation

Tibial component varus malalignment (i.e., less than 0-3 degrees valgus, or frankly varus) is strongly correlated with early aseptic loosening, particularly on the medial side. A varus alignment shifts the load medially, leading to increased stress on the medial bone-implant interface and polyethylene wear. A tibial component placed in 5 degrees of valgus is generally considered within an acceptable range (often 0-3 degrees valgus). Femoral component malalignment or overall mechanical axis restoration would impact loosening differently or not be the primary driver fortibialcomponent aseptic loosening in this scenario.

Question 5885

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 5886

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 5887

Topic: 3. Adult Reconstruction (Hip & Knee)

A 55-year-old active male reports persistent knee stiffness and difficulty achieving full flexion after TKA. Radiographs show a well-aligned implant without obvious issues. What subtle malalignment or technical error could contribute to this 'tight knee' sensation, particularly in flexion?

. Tibial component placed with excessive posterior slope
. Femoral component undersizing
. Oversizing of the femoral component
. Insufficient posterior soft tissue release
. Femoral component placed in excessive external rotation

Correct Answer & Explanation

. Oversizing of the femoral component

Explanation

Oversizing of the femoral component (especially in the anterior-posterior dimension) can lead to a 'tight' flexion gap by effectively increasing the volume within the knee, preventing full flexion. It can also cause impingement of the posterior capsule or soft tissues. Excessive tibial posterior slope typically leads to a loose flexion gap. Femoral component undersizing can cause instability or aseptic loosening. Insufficient posterior soft tissue release would make extension difficult, rather than flexion. Excessive femoral external rotation can cause medial laxity and not necessarily stiffness.

Question 5888

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 5889

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary biomechanical advantage of achieving a neutral mechanical axis (0 ± 3 degrees varus/valgus) in TKA?

. Increased range of motion in flexion
. Reduced risk of patellofemoral instability
. Even distribution of load across the tibial polyethylene insert
. Prevention of peri-prosthetic infection
. Faster rehabilitation

Correct Answer & Explanation

. Even distribution of load across the tibial polyethylene insert

Explanation

The primary biomechanical advantage of achieving a neutral mechanical axis in TKA is the even distribution of load across the tibial polyethylene insert. This minimizes peak stresses on one side, which is critical for reducing polyethylene wear, preventing aseptic loosening, and improving the long-term survival of the implant. While other benefits may exist, load distribution is paramount for longevity.

Question 5890

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 5891

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 5892

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 5893

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 5894

Topic: 3. Adult Reconstruction (Hip & Knee)

When assessing TKA alignment on postoperative radiographs, what is the acceptable range for the mechanical axis in the coronal plane?

. 5 degrees varus to 5 degrees valgus
. 3 degrees varus to 3 degrees valgus
. 0-2 degrees varus
. 0-2 degrees valgus
. Always perfectly 0 degrees

Correct Answer & Explanation

. 3 degrees varus to 3 degrees valgus

Explanation

The generally accepted range for achieving optimal mechanical axis in the coronal plane post-TKA is within 3 degrees of neutral (i.e., 3 degrees varus to 3 degrees valgus). Malalignment outside this range has been shown to be associated with increased rates of polyethylene wear and aseptic loosening. While a perfectly neutral axis is ideal, a small deviation is tolerated.

Question 5895

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 5896

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.

Question 5897

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 5898

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 5899

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 5900

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the primary concern with gross oversizing of the tibial component in TKA?

. Increased polyethylene wear
. Stress shielding of the proximal tibia
. Impingement of the soft tissues (e.g., MCL, pes anserinus)
. Subsidence of the component
. Increased bone stock for future revision

Correct Answer & Explanation

. Impingement of the soft tissues (e.g., MCL, pes anserinus)

Explanation

Gross oversizing of the tibial component, particularly anteriorly, posteriorly, or medially/laterally, can lead to impingement of the surrounding soft tissues (e.g., patellar tendon, posterior capsule, MCL, pes anserinus tendons). This can cause pain, stiffness, and reduced range of motion. While stress shielding can occur with any implant, and wear is multifactorial, direct impingement is a more immediate and painful consequence of oversizing. Undersizing is more associated with subsidence.

Test Yourself

Switch to an interactive, timed exam simulation to truly master this topic.

On this Page