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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 325 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 6481

Topic: 3. Adult Reconstruction (Hip & Knee)

Which of the following is the most likely consequence of significantly elevating the joint line during a revision total knee arthroplasty?

. Decreased patellofemoral contact forces
. Mid-flexion instability
. Pseudo-patella alta
. Increased range of flexion
. Tight extension gap

Correct Answer & Explanation

. Mid-flexion instability

Explanation

Elevating the joint line often requires a thicker polyethylene insert to balance extension, which can lead to mid-flexion instability because the collateral ligaments are relatively lax in mid-flexion. It also results in pseudo-patella baja, not alta.

Question 6482

Topic: 3. Adult Reconstruction (Hip & Knee)

During a total knee arthroplasty, the femoral component is inadvertently placed in excessive internal rotation relative to the transepicondylar axis. Which of the following complications is most likely to occur?

. Medial patellar subluxation
. Loose medial flexion gap
. Tight lateral flexion gap
. Lateral patellar subluxation and a tight medial flexion gap
. Symmetrical restriction of the flexion gap

Correct Answer & Explanation

. Lateral patellar subluxation and a tight medial flexion gap

Explanation

Internal rotation of the femoral component relative to the transepicondylar axis lateralizes the trochlear groove, increasing the Q angle and leading to lateral patellar subluxation. It also tightens the medial flexion gap and loosens the lateral flexion gap.

Question 6483

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient presents with a painful popping sensation at 30 degrees of flexion as they extend their knee from a fully flexed position, one year after a posterior-stabilized total knee arthroplasty. What is the most likely etiology?

. Patellofemoral overstuffing
. Fibrous nodule impinging in the intercondylar notch
. Polyethylene wear debris
. Undersized femoral component
. Impingement of the posterior cruciate ligament

Correct Answer & Explanation

. Fibrous nodule impinging in the intercondylar notch

Explanation

This classic presentation describes patellar clunk syndrome, which occurs in posterior-stabilized TKA. A fibrous nodule develops on the superior pole of the patella and catches in the intercondylar box of the femoral component as the knee extends from a flexed position.

Question 6484

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient with a painful TKA is being evaluated for a periprosthetic joint infection (PJI). Synovial fluid analysis reveals a highly elevated alpha-defensin level. What is the primary biological function of alpha-defensin in this context?

. It is an antimicrobial peptide released by activated neutrophils
. It is an acute-phase reactant produced primarily by the liver
. It is a byproduct of bacterial biofilm metabolism
. It is a degradation product of native articular cartilage
. It is an enzyme that aggressively degrades ultra-high-molecular-weight polyethylene

Correct Answer & Explanation

. It is an antimicrobial peptide released by activated neutrophils

Explanation

Alpha-defensin is a biomarker released by neutrophils in response to pathogens. It serves as an antimicrobial peptide and is highly sensitive and specific for diagnosing periprosthetic joint infection.

Question 6485

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient undergoing a primary total knee arthroplasty (TKA), the femoral component is inadvertently placed in excessive internal rotation. Which of the following postoperative clinical findings is most likely to occur?

. Lateral patellar tilt and subluxation
. Medial patellar tilt and subluxation
. Symmetric extension space tightness
. Symmetrical mid-flexion instability
. Patellar clunk syndrome

Correct Answer & Explanation

. Lateral patellar tilt and subluxation

Explanation

Internal rotation of the femoral component shifts the trochlear groove medially, which effectively increases the Q-angle. This alters patellofemoral kinematics, frequently resulting in lateral patellar tracking issues such as tilt, subluxation, or dislocation.

Question 6486

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, after making the standard bone cuts, the surgeon evaluates the gaps. The joint is tight in flexion and symmetric in extension. Which of the following is the most appropriate next surgical step?

. Recut the proximal tibia
. Release the posterior capsule
. Increase the femoral component size
. Downsize the femoral component
. Release the superficial medial collateral ligament

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A gap that is tight in flexion but symmetric and well-balanced in extension requires an isolated increase in the flexion gap. This is best achieved by downsizing the femoral component or by increasing the posterior slope of the tibial cut.

Question 6487

Topic: 3. Adult Reconstruction (Hip & Knee)

In the correction of a fixed valgus deformity during a total knee arthroplasty, the lateral compartment is found to be tight in full extension but balanced in 90 degrees of flexion. Which of the following structures is the primary tether and should be selectively released first?

. Popliteus tendon
. Posterolateral corner
. Iliotibial (IT) band
. Lateral collateral ligament (LCL)
. Biceps femoris tendon

Correct Answer & Explanation

. Iliotibial (IT) band

Explanation

The iliotibial (IT) band primarily acts as a lateral tether in full extension but relaxes in flexion. If the lateral side is tight only in extension, isolated pie-crusting or release of the IT band is indicated.

Question 6488

Topic: Total Knee Arthroplasty (TKA)

During a complex revision TKA, the surgeon inadvertently elevates the joint line by 8 mm compared to the native knee. This technical error is most likely to result in which of the following biomechanical consequences?

. Mid-flexion instability
. Decreased patellofemoral contact forces
. Improved maximum knee flexion
. Proximal migration of the patella relative to the femur
. Excessive tightening of the collateral ligaments in extension

Correct Answer & Explanation

. Mid-flexion instability

Explanation

Elevating the joint line often necessitates using a thicker polyethylene insert to balance the extension gap. This alters the isometry of the collateral ligaments, leading to relative laxity and instability in mid-flexion, as well as patella baja.

Question 6489

Topic: Total Knee Arthroplasty (TKA)

A patient presents with a painful "catch" and a palpable pop at the anterior aspect of the knee when extending from 40 degrees of flexion to full extension, 9 months following a posterior-stabilized TKA. What is the primary pathoanatomy driving this clinical presentation?

. Fibrous nodule formation on the posterior aspect of the quadriceps tendon
. An overhanging anterior flange of the femoral component
. Subluxation of the patella over the medial femoral condyle
. Impingement of the tibial post against the intercondylar notch
. Asymmetric wear of the polyethylene insert

Correct Answer & Explanation

. Fibrous nodule formation on the posterior aspect of the quadriceps tendon

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA when a fibrous nodule forms on the posterior quadriceps tendon just superior to the patella. As the knee extends, this nodule catches in the intercondylar box of the femoral component and abruptly pops out.

Question 6490

Topic: 3. Adult Reconstruction (Hip & Knee)

When sizing the tibial component during a primary TKA, oversizing the component in the mediolateral dimension is most directly associated with which of the following postoperative complications?

. Patellar maltracking
. Posterior cruciate ligament impingement
. Pain secondary to soft tissue impingement
. Early aseptic loosening from stress shielding
. Excessive external rotation of the tibial tubercle

Correct Answer & Explanation

. Pain secondary to soft tissue impingement

Explanation

Mediolateral overhang of the tibial component frequently irritates the surrounding soft tissues, such as the medial collateral ligament (MCL) medially or the popliteus/IT band laterally. This impingement leads to persistent postoperative pain.

Question 6491

Topic: 3. Adult Reconstruction (Hip & Knee)

During a primary total knee arthroplasty (TKA), trial reduction demonstrates a gap that is symmetric and well-balanced in full extension, but the knee is significantly tight in 90 degrees of flexion. Which of the following adjustments is the most appropriate next step to balance the knee?

. Increase the posterior slope of the tibial cut
. Resect more proximal tibia
. Downsize the femoral component
. Release the posterior capsule
. Upsize the femoral component

Correct Answer & Explanation

. Downsize the femoral component

Explanation

Downsizing the femoral component increases the flexion gap without altering the extension gap. Increasing the posterior tibial slope also increases the flexion gap but alters tibial bone stock, while resecting more proximal tibia affects both flexion and extension gaps symmetrically.

Question 6492

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoes a revision total knee arthroplasty utilizing thick polyethylene inserts to address a severe flexion gap laxity, which ultimately elevates the joint line by 10 mm. Which of the following complications is most directly associated with this joint line elevation?

. True patella baja
. Pseudo-patella baja
. Decreased patellofemoral contact forces
. Recurvatum deformity
. Mid-flexion stability improvement

Correct Answer & Explanation

. Pseudo-patella baja

Explanation

Elevating the joint line during TKA lowers the patella relative to the new joint line, resulting in pseudo-patella baja. This alters patellofemoral tracking, limits knee flexion, and can increase anterior knee pain.

Question 6493

Topic: 3. Adult Reconstruction (Hip & Knee)

In a patient who recently underwent total knee arthroplasty, combined internal rotation malalignment of both the femoral and tibial components will most likely result in which of the following?

. Medial patellar subluxation
. Lateral patellar subluxation
. Increased flexion gap symmetry
. PCL avulsion

Correct Answer & Explanation

. Lateral patellar subluxation

Explanation

Internal rotation of the femoral and tibial components increases the Q-angle dynamically. This creates a severe laterally directed force vector on the extensor mechanism, leading to lateral patellar subluxation or dislocation.

Question 6494

Topic: Total Knee Arthroplasty (TKA)

The primary objective of using 'kinematic alignment' principles rather than traditional 'mechanical alignment' in total knee arthroplasty is to:

. Ensure the tibial cut is strictly perpendicular to the tibial mechanical axis
. Recreate the patient's individual pre-arthritic constitutional joint lines
. Release the MCL universally to achieve perfectly symmetric gaps
. Mandate a 3-degree external rotation of the femoral component relative to the posterior condyles

Correct Answer & Explanation

. Recreate the patient's individual pre-arthritic constitutional joint lines

Explanation

Kinematic alignment aims to restore the patient's pre-arthritic native joint lines and normal knee kinematics by co-aligning the components with the three kinematic axes of the knee, minimizing the need for soft tissue releases.

Question 6495

Topic: Total Knee Arthroplasty (TKA)

During a TKA for a severe, fixed valgus knee deformity, a lateral soft tissue release is required. If the knee is found to be tight exclusively in flexion but balanced in extension, which lateral structure is the most appropriate initial target for release?

. Iliotibial band (ITB)
. Lateral collateral ligament (LCL)
. Popliteus tendon
. Posterolateral capsule

Correct Answer & Explanation

. Popliteus tendon

Explanation

The popliteus tendon is a primary restraint to flexion on the lateral side of the knee. Releasing the popliteus preferentially opens the lateral flexion gap, whereas releasing the ITB preferentially affects the lateral extension gap.

Question 6496

Topic: 3. Adult Reconstruction (Hip & Knee)
In a mechanically well-aligned, perfectly balanced TKA utilizing conventional ultra-high-molecular-weight polyethylene (UHMWPE), what is the primary tribological wear mechanism that generates the submicron particles responsible for osteolysis?
. Delamination wear
. Adhesive wear
. Third-body wear
. Fatigue wear

Correct Answer & Explanation

. Adhesive wear

Explanation

Adhesive wear occurs during normal articulation as microscopic asperities on the articular surfaces bond and break apart. This is the primary mechanism generating millions of submicron UHMWPE particles, which are the main culprits in macrophage-mediated osteolysis.

Question 6497

Topic: 3. Adult Reconstruction (Hip & Knee)

When planning a total knee arthroplasty in a patient with an extra-articular diaphyseal malunion, what is the generally accepted threshold for a coronal plane tibial deformity beyond which a concurrent tibial osteotomy is recommended over an intra-articular compensatory resection?

. 5 degrees
. 10 degrees
. 20 degrees
. 25 degrees
. 30 degrees

Correct Answer & Explanation

. 10 degrees

Explanation

For tibial extra-articular deformities, a coronal deformity >10 to 15 degrees generally dictates a concurrent osteotomy. Intra-articular correction of larger deformities risks asymmetric bone resection and compromise of the collateral ligament insertions.

Question 6498

Topic: 3. Adult Reconstruction (Hip & Knee)

A total knee arthroplasty is planned using conventional instrumentation on a patient with excessive anterior bowing of the femoral diaphysis. If a standard long straight intramedullary alignment rod is used to direct the distal femoral cut, what is the most likely error in component positioning?

. Excessive extension of the femoral component
. Excessive flexion of the femoral component
. Excessive varus of the femoral component
. Excessive valgus of the femoral component
. Anterior notching of the distal femur

Correct Answer & Explanation

. Excessive flexion of the femoral component

Explanation

A straight intramedullary rod placed into an excessively anterior-bowed femur will dictate a relatively extended distal femoral cut compared to the true mechanical axis. This results in the femoral component being placed in excessive flexion.

Question 6499

Topic: 3. Adult Reconstruction (Hip & Knee)

During a revision total knee arthroplasty, excessive distal femoral bone loss is managed with a standard femoral component and a thick polyethylene insert, resulting in a 12 mm elevation of the joint line. Which of the following is the most likely postoperative clinical consequence?

. Patella alta with extensor lag
. Mid-flexion instability and pseudo-patella baja
. Severe recurvatum during stance phase
. Increased maximal knee flexion
. Excessive tightening of the posterior cruciate ligament

Correct Answer & Explanation

. Mid-flexion instability and pseudo-patella baja

Explanation

Elevating the joint line alters the isometry of the collateral ligaments, frequently leading to mid-flexion instability. It also moves the joint line closer to the tibial tubercle, causing pseudo-patella baja which limits knee flexion.

Question 6500

Topic: Total Knee Arthroplasty (TKA)

A surgeon plans an intra-articular compensatory bone cut to correct a 12-degree extra-articular diaphyseal tibial varus deformity during a TKA. What is the primary risk associated with making an aggressively asymmetric intra-articular tibial resection to achieve a neutral mechanical axis?

. Creation of a patella alta
. Avulsion of the tibial tubercle
. Compromise of the medial collateral ligament tibial insertion
. Iatrogenic injury to the popliteal artery
. Excessive external rotation of the tibial component

Correct Answer & Explanation

. Compromise of the medial collateral ligament tibial insertion

Explanation

Compensating for a large extra-articular varus deformity intra-articularly requires removing a much larger wedge of lateral bone relative to the medial side. If the deformity is severe, making the required minimal medial cut risks completely detaching the superficial MCL insertion.

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