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Total Knee Arthroplasty (TKA) MCQs

Practice Set 19 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 361

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old woman who underwent total knee replacement 18 months ago has had 3 weeks of moderate

drainage from a previously healed wound. What is the most appropriate treatment?

. Vacuum-assisted wound closure dressing
. Intravenous antibiotics for 6 weeks, followed by long-term oral antibiotic administration
. Irrigation and debridement, followed by polyethylene exchange
. Two-stage debridement and reconstruction

Correct Answer & Explanation

. Vacuum-assisted wound closure dressing

Explanation

This situation represents a definitively and chronically infected knee replacement. Antibiotic therapy alone might suppress the infection but would not eradicate it. Debridement and polyethylene exchange would be appropriate treatment for an early postoperative infection. The treatment of choice is to perform a two-stage debridement and reconstruction. Although not among the listed choices, an aspiration or culture could be done presurgically and might help clinicians identify the best antibiotics to treat the condition. Antibiotic selection would not affect the need for the two-stage reconstruction, however.

Question 362

Topic: Total Knee Arthroplasty (TKA)

Figure below shows the standing AP radiograph obtained from a 55-year-old man who has a 5-year history

of daily left knee medial joint line pain with weight-bearing activities. He denies night pain or symptoms of instability. On examination, his range of motion is 0° to 140°. He has a mild, fully correctable varus deformity and a negative Lachman test result. Nonsurgical treatment has failed. Unicompartmental knee arthroplasty (UKA) is discussed with the patient. The most appropriate next radiographic evaluation should be

. MRI of the left knee to evaluate the lateral compartment.
. a CT arthrogram to evaluate the status of the medial and lateral meniscus.
. a stress radiograph to evaluate correction of the varus deformity.
. a sunrise view to determine the status of the patellofemoral joint.

Correct Answer & Explanation

. MRI of the left knee to evaluate the lateral compartment.

Explanation

A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact anterior cruciate ligament (ACL). The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progressfaster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.

Question 363

Topic: Total Knee Arthroplasty (TKA)

A 74-year-old male sustains a traumatic patellar tendon rupture three years after a primary total knee arthroplasty (TKA). The implants are well-fixed. Attempts at primary repair with wire augmentation have failed, leaving the patient with a 45-degree extensor lag. What is the most appropriate and reliable surgical intervention to reconstruct the extensor mechanism?

. Revision primary repair with autologous hamstring graft overlay
. Medial gastrocnemius rotational flap
. Extensor mechanism allograft reconstruction
. Revision to a hinged TKA system
. Arthroscopic lysis of adhesions and manipulation under anesthesia

Correct Answer & Explanation

. Revision primary repair with autologous hamstring graft overlay

Explanation

Chronic or failed extensor mechanism ruptures following TKA are devastating complications. Because the local tissues are compromised, primary repair is associated with a very high failure rate. The gold standard reconstructive option for a chronic/failed patellar tendon rupture post-TKA (with well-fixed components) is a complete extensor mechanism allograft (tibial tubercle, patellar tendon, patella, and quadriceps tendon) or synthetic mesh reconstruction.

Question 364

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents with a painful catch and an audible 'clunk' as her knee moves from 45 to 30 degrees of extension. She underwent a posterior-stabilized TKA 18 months ago. What is the pathophysiology underlying this complication?

. A fibrous nodule on the superior pole of the patella catching in the intercondylar box
. The popliteus tendon snapping over the lateral femoral condyle
. Friction between the iliotibial band and the femoral component
. Patellar maltracking due to internal rotation of the tibial component
. An overstuffed patella restricting terminal extension

Correct Answer & Explanation

. A fibrous nodule on the superior pole of the patella catching in the intercondylar box

Explanation

Patellar clunk syndrome is a complication seen primarily in posterior-stabilized (PS) TKAs. It occurs when a fibrous nodule develops on the posterior surface of the superior pole of the patella. As the knee extends from a flexed position (around 30-45 degrees), this nodule catches in the femoral intercondylar box and pops out with an audible and painful clunk.

Question 365

Topic: Total Knee Arthroplasty (TKA)

Which of the following statements best describes the core principle of 'kinematic alignment' in total knee arthroplasty, as opposed to traditional 'mechanical alignment'?

. Restoring the mechanical axis to 0 degrees relative to the weight-bearing line
. Aligning the femoral component strictly parallel to the surgical transepicondylar axis
. Restoring the patient's individual pre-arthritic joint lines and kinematic axes
. Routinely externally rotating the femoral component by 3 degrees
. Releasing collateral ligaments heavily to create equal rectangular gaps

Correct Answer & Explanation

. Restoring the mechanical axis to 0 degrees relative to the weight-bearing line

Explanation

Kinematic alignment aims to position the TKA components such that they restore the patient's native, pre-arthritic joint line and the three kinematic axes of the knee. This is in contrast to mechanical alignment, which seeks to create a neutral mechanical axis (0 degrees) with cuts perpendicular to the mechanical axes of the femur and tibia, often necessitating soft tissue releases.

Question 366

Topic: Total Knee Arthroplasty (TKA)

During a posterior-stabilized TKA, trial components are inserted. The knee is perfectly balanced and stable in full extension, but it is significantly tight in 90 degrees of flexion. What is the most appropriate intraoperative step to achieve a balanced gap?

. Resect more distal femur
. Downsize the femoral component and use a thicker polyethylene insert
. Downsize the femoral component using an anterior referencing guide
. Release the posterior capsule
. Resect more proximal tibia

Correct Answer & Explanation

. Downsize the femoral component using an anterior referencing guide

Explanation

If the knee is balanced in extension but tight in flexion, the flexion gap must be increased selectively. Downsizing the femoral component using an anterior referencing system keeps the anterior flange flush but resects more posterior condylar bone, selectively opening the flexion gap without affecting the balanced extension gap.

Question 367

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old male sustains an acute, complete rupture of the patellar tendon 3 weeks following a primary TKA. Radiographs show the implants are perfectly positioned and well-fixed. What is the most reliable surgical management for this devastating complication?

. Direct primary repair with heavy non-absorbable sutures
. Direct primary repair augmented with an unyielding cerclage wire
. Reconstruction using a complete fresh-frozen extensor mechanism allograft
. Arthrodesis of the knee
. Revision to a constrained condylar knee (CCK)

Correct Answer & Explanation

. Reconstruction using a complete fresh-frozen extensor mechanism allograft

Explanation

Complete extensor mechanism disruption after a TKA has notoriously poor outcomes when managed with direct repair, even with wire augmentation. The most reliable and accepted salvage procedure, assuming well-fixed implants, is reconstruction with a complete extensor mechanism allograft (or occasionally synthetic mesh).

Question 368

Topic: Total Knee Arthroplasty (TKA)

In the emerging paradigm of Kinematic Alignment (KA) for Total Knee Arthroplasty, what is the primary overarching goal regarding the final positioning of the components?

. To place both components strictly orthogonal (90 degrees) to the mechanical axis of the lower extremity
. To align the components parallel to the surgical transepicondylar axis to balance collateral ligaments
. To restore the patient's exact pre-arthritic native joint lines and individual physiologic kinematics
. To systematically position the tibial cut in exactly 3 degrees of varus and the femur in 5 degrees of valgus
. To perform step-wise collateral ligament releases to achieve perfectly symmetric rectangular flexion and extension gaps

Correct Answer & Explanation

. To restore the patient's exact pre-arthritic native joint lines and individual physiologic kinematics

Explanation

Kinematic Alignment (KA) aims to co-align the axes of the components with the three native kinematic axes of the knee, effectively restoring the patient's unique pre-arthritic joint line, thereby resurfacing the joint without the need for routine ligament releases. This contrasts with Mechanical Alignment (MA) which dictates orthogonal bone cuts.

Question 369

Topic: Total Knee Arthroplasty (TKA)

Which of the following describes the fundamental goal of 'Kinematic Alignment' in total knee arthroplasty compared to traditional 'Mechanical Alignment'?

. To cut the femur and tibia strictly perpendicular to their mechanical axes
. To intentionally create a postoperative limb alignment of exactly 0 degrees mechanical axis
. To co-align the transverse axes of the components with the three kinematic axes of the normal knee
. To externally rotate the femoral component 3 degrees off the posterior condylar axis in all patients
. To release the medial collateral ligament to achieve rectangular flexion and extension gaps

Correct Answer & Explanation

. To co-align the transverse axes of the components with the three kinematic axes of the normal knee

Explanation

Kinematic alignment (KA) aims to restore the pre-arthritic constitutional alignment and kinematics of the knee by co-aligning the transverse axes of the TKA components with the native kinematic axes of the joint. This often involves placing the tibial component in slight varus and the femoral component in slight valgus (matching the native joint line), minimizing the need for soft-tissue releases. Mechanical alignment aims for a neutral (0 degree) mechanical axis with cuts perpendicular to the mechanical axes of the tibia and femur.

Question 370

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents with an audible and palpable 'clunk' at 40 degrees of flexion as she extends her knee, 1 year after a posterior-stabilized TKA. Which of the following implant design factors is most directly associated with the development of patellar clunk syndrome?

. High ratio of the femoral intercondylar box height to the patellar button diameter
. Anterior placement of the femoral component
. Thickening of the patellar component
. A sharp, square anterior-superior edge of the femoral intercondylar box
. A lowered joint line during tibial preparation

Correct Answer & Explanation

. A sharp, square anterior-superior edge of the femoral intercondylar box

Explanation

Patellar clunk syndrome occurs primarily in posterior-stabilized TKA due to the formation of a fibrous nodule at the superior pole of the patella. This nodule catches in the intercondylar box of the femoral component during extension (typically around 30-45 degrees of flexion). Older PS designs with a sharp, square anterior-superior edge of the intercondylar box were highly associated with this complication. Modern designs have lowered and rounded this edge, decreasing the incidence.

Question 371

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, a surgeon uses a reciprocating saw to complete the posterior condylar cuts and inadvertently injures the popliteal artery. Anatomically, at what level does the popliteal artery run closest to the posterior capsule of the knee joint, making it most vulnerable to injury during TKA?

. At the level of the joint line, directly posterior to the posterior cruciate ligament
. At the level of the distal femoral cut, lateral to the midline
. At the level of the tibial cut, just inferior to the joint line
. At the level of the adductor hiatus
. At the origin of the anterior tibial artery

Correct Answer & Explanation

. At the level of the tibial cut, just inferior to the joint line

Explanation

The popliteal artery is closest to the posterior capsule and bone at the level of the proximal tibial bone cut (just distal to the joint line). Studies show the distance from the posterior tibial cortex to the artery can be as little as 2-3 mm. Furthermore, it is tethered at the soleal arch, making it immobile and highly susceptible to injury from penetrating instruments (like a saw blade plunging past the posterior cortex) during the tibial resection.

Question 372

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old male presents with inability to perform a straight leg raise 6 months after a TKA. Examination and ultrasound reveal a chronic, complete rupture of the patellar tendon with a 4 cm gap. The tibial tubercle is intact, and the components are well-fixed. What is the most reliable surgical reconstruction method for this chronic defect?

. Primary end-to-end repair with non-absorbable suture
. Primary repair augmented with semitendinosus autograft
. Reconstruction using synthetic mesh or extensor mechanism allograft
. Gastrocnemius rotational flap
. Conversion to a fixed-hinge knee prosthesis

Correct Answer & Explanation

. Reconstruction using synthetic mesh or extensor mechanism allograft

Explanation

Chronic patellar tendon ruptures post-TKA with significant gap formation cannot be treated successfully with primary repair (tissue is poor quality, high failure rate). The gold standard treatments for chronic extensor mechanism disruption post-TKA are either an extensor mechanism allograft (using a block of tibial bone, patellar tendon, patella, and quadriceps tendon) or reconstruction using synthetic mesh (e.g., Marlex mesh). Both have shown comparable, reasonable salvage rates in modern literature, vastly outperforming primary repair or autograft augmentation in the setting of TKA.

Question 373

Topic: Total Knee Arthroplasty (TKA)

In the context of kinematic alignment for primary TKA, the procedure aims to restore the pre-arthritic native joint lines. When compared to traditional mechanical alignment, what is the most characteristic coronal alignment profile of the final components in a patient with constitutional varus?

. A femoral component in valgus and a tibial component in valgus
. A femoral component in relative valgus and a tibial component in relative varus
. A femoral component in relative varus and a tibial component in relative valgus
. A femoral component in 0 degrees and a tibial component in 0 degrees to the mechanical axis
. A femoral component in relative varus and a tibial component in relative varus

Correct Answer & Explanation

. A femoral component in relative valgus and a tibial component in relative varus

Explanation

Constitutional varus usually arises from a combination of distal femoral valgus (relative to the mechanical axis) and proximal tibial varus (joint line obliquity). Kinematic alignment (KA) aims to co-align the axes of the components with the three kinematic axes of the knee, effectively restoring the patient's native joint line. In a patient with constitutional varus, this typically results in the femoral component being placed in slightly more valgus (compared to the mechanical axis cut of 0 degrees) and the tibial component being placed in varus to match the native proximal tibial joint line obliquity.

Question 374

Topic: Total Knee Arthroplasty (TKA)

A patient presents with persistent lateral patellar subluxation and anterior knee pain after a primary TKA. A postoperative CT scan is obtained to evaluate component rotation. Which combination of component malrotation is the most common cause of iatrogenic lateral patellar tracking?

. External rotation of the femoral component and external 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
. Internal rotation of the femoral component and internal rotation of the tibial component
. Neutral rotation of the femoral component and external rotation of the tibial component

Correct Answer & Explanation

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

Explanation

Internal rotation of the femoral component shifts the trochlear groove medially, while internal rotation of the tibial component effectively lateralizes the tibial tubercle relative to the trochlea. Both of these rotational errors increase the Q-angle, exacerbating lateral patellar maltracking and anterior knee pain.

Question 375

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old woman presents with persistent lateral anterior knee pain and clinical evidence of lateral patellar subluxation 1 year after a primary TKA. During revision surgery, malrotation of the components is suspected. Which of the following technical errors is the most common cause of lateral patellar maltracking in TKA?

. External rotation of the femoral component
. Internal rotation of the femoral component
. External rotation of the tibial component
. Medial placement of the patellar component
. Distalization of the joint line

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of either the femoral or tibial component relative to their anatomical axes increases the Q-angle, leading to lateral patellar maltracking. To optimize patellar tracking, the femoral component is typically externally rotated (relative to the posterior condylar axis) and the patellar button is placed medially.

Question 376

Topic: Total Knee Arthroplasty (TKA)

A patient presents with persistent anterior knee pain and a subjective feeling of instability 6 months following a primary TKA. Standing radiographs demonstrate a significantly elevated joint line and secondary patella baja. Which of the following complications is most specifically associated with an elevated joint line in TKA?

. Increased risk of patellar clunk syndrome
. Mid-flexion instability
. Decreased patellofemoral contact pressure
. Hyperextension recurvatum
. Paradoxical anterior sliding

Correct Answer & Explanation

. Mid-flexion instability

Explanation

Elevation of the joint line during TKA often results from excessive distal femoral resection combined with a thicker tibial polyethylene insert to balance the extension gap. This alters the isometry of the collateral ligaments as the knee moves through the arc of motion, leading to laxity in mid-flexion (mid-flexion instability). It also leads to relative patella baja, causing anterior knee pain.

Question 377

Topic: Total Knee Arthroplasty (TKA)

A surgeon is performing a cruciate-retaining TKA. With trial components in place, the knee is well-balanced in extension but exhibits excessive tightness and limited range of motion in flexion, along with paradoxical anterior tibial translation. What is the primary anatomical structure responsible for this finding?

. Medial collateral ligament
. Lateral collateral ligament
. Posterior capsule
. Posterior cruciate ligament
. Quadriceps tendon

Correct Answer & Explanation

. Posterior cruciate ligament

Explanation

In a cruciate-retaining TKA, an excessively tight posterior cruciate ligament prevents normal posterior femoral rollback. This causes the flexion gap to be excessively tight and leads to paradoxical anterior sliding of the femur on the tibia during flexion.

Question 378

Topic: Total Knee Arthroplasty (TKA)

A patient with a failed TKA requires revision surgery. The surgeon identifies an AORI Type 3 defect, characterized by severe metaphyseal bone loss that compromises the origins of the collateral ligaments. Which of the following constraint levels is definitively required?

. Cruciate-retaining (CR)
. Posterior-stabilized (PS)
. Constrained condylar knee (CCK)
. Rotating-hinge prosthesis
. Unicompartmental knee

Correct Answer & Explanation

. Rotating-hinge prosthesis

Explanation

AORI Type 3 defects involve massive bone loss that compromises the medial and lateral collateral ligament attachments. A rotating-hinge implant provides linked stability and is required to substitute for profound collateral ligament deficiency.

Question 379

Topic: Total Knee Arthroplasty (TKA)

Following implantation of trial components in a TKA, the surgeon notes a tendency for lateral patellar subluxation. Both the flexion and extension gaps are symmetric and balanced. Which of the following technical errors is most likely responsible?

. External rotation of the tibial component
. Internal rotation of the femoral component
. Lateral translation of the femoral component
. Medializing the patellar button
. Excessive valgus cut of the distal femur

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, leading to lateral patellar tracking. Externally rotating the components or medializing the patellar dome improves central patellar tracking.

Question 380

Topic: Total Knee Arthroplasty (TKA)

When choosing between a cruciate-retaining (CR) and a posterior-stabilized (PS) TKA design, the surgeon must consider implant kinematics. A PS TKA relies on the cam-post mechanism to specifically substitute for which native function?

. Posterior femoral rollback during deep flexion
. Varus-valgus stability in full extension
. Prevention of anterior tibial translation in extension
. Medial pivot rotation during early flexion
. Patellar tracking in the proximal trochlear groove

Correct Answer & Explanation

. Posterior femoral rollback during deep flexion

Explanation

The intact posterior cruciate ligament (PCL) drives posterior femoral rollback during deep knee flexion to maximize flexion angle and clear the posterior anatomy. In a PS TKA, the PCL is excised, and the cam-post mechanism engages to recreate this essential rollback.

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