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Total Knee Arthroplasty (TKA) MCQs

Practice Set 7 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 121

Topic: Total Knee Arthroplasty (TKA)

The concept of kinematic alignment in total knee arthroplasty has gained popularity in recent years. How does the fundamental goal of kinematic alignment differ from that of traditional mechanical alignment?

. It aims to resect bone perpendicular to the mechanical axis of the lower limb universally
. It aims to restore the patient's pre-arthritic, patient-specific joint line obliquity and native axes of rotation
. It mandates extensive ligamentous releases to create equal rectangular gaps in all patients
. It requires placing the femoral component in exactly 3 degrees of external rotation relative to the posterior condylar axis
. It focuses primarily on adjusting the tibial slope to match the contralateral knee

Correct Answer & Explanation

. It aims to resect bone perpendicular to the mechanical axis of the lower limb universally

Explanation

Traditional mechanical alignment aims for a neutral (0 degree) mechanical axis, cutting the distal femur and proximal tibia perpendicular to their mechanical axes and relying on ligament releases for balancing. Kinematic alignment aims to restore the patient's individual pre-arthritic anatomy, keeping the native joint line obliquity and axes of rotation intact, which theoretically reduces the need for soft tissue releases and improves patient satisfaction.

Question 122

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA, the surgeon utilizes kinematic alignment principles. Which of the following statements best describes the fundamental goal of kinematic alignment compared to traditional mechanical alignment?

. Positioning both the femoral and tibial components exactly perpendicular to the mechanical axis
. Restoring the pre-arthritic native joint lines and soft tissue laxity without extensive ligament releases
. Creating a joint line that is strictly perpendicular to the floor during stance phase
. Releasing the medial collateral ligament to correct a fixed varus deformity to neutral
. Under-sizing the tibial component to allow for maximum rotational freedom

Correct Answer & Explanation

. Positioning both the femoral and tibial components exactly perpendicular to the mechanical axis

Explanation

Kinematic alignment aims to restore the patient's native constitutional alignment and joint surface orientation. By doing so, it theoretically restores natural ligament tension, thereby minimizing or eliminating the need for soft tissue releases.

Question 123

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old male undergoes a primary TKA. In the recovery room, he is noted to have a dense foot drop and numbness over the dorsum of the foot. Which of the following preoperative deformities places the patient at the highest risk for this specific complication?

. Fixed varus deformity of 15 degrees
. Fixed valgus deformity of 20 degrees
. Flexion contracture of 10 degrees
. Genu recurvatum of 5 degrees
. Patella alta

Correct Answer & Explanation

. Fixed varus deformity of 15 degrees

Explanation

Correction of a severe, fixed valgus deformity can lead to sudden tensioning and stretch of the common peroneal nerve. This makes valgus knees the highest risk profile for postoperative peroneal nerve palsy in TKA.

Question 124

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old male complains of knee instability and swelling 18 months following a posterior-stabilized total knee arthroplasty. On examination, the knee is stable in full extension and at 90 degrees of flexion, but exhibits marked laxity to varus and valgus stress at 30 to 45 degrees of flexion. Which of the following technical errors most likely caused this specific pattern of instability?

. Undersizing the femoral component
. Excessive posterior tibial slope
. Joint line elevation
. Failure to resurface the patella
. Inadequate release of the posterior cruciate ligament

Correct Answer & Explanation

. Undersizing the femoral component

Explanation

Mid-flexion instability in a TKA typically results from joint line elevation. When the joint line is elevated (often due to excessive distal femoral resection compensated by a thicker polyethylene liner), the collateral ligaments are balanced in extension and 90 degrees of flexion but become lax in mid-flexion.

Question 125

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old female presents with persistent lateral-sided knee pain and a palpable, painful snapping sensation during active flexion 6 months after a primary posterior-stabilized TKA. Radiographs reveal well-fixed, appropriately sized components. Dynamic ultrasound confirms the popliteus tendon snapping over the edge of the femoral component. What is the most appropriate management?

. Immediate revision to a constrained condylar knee
. Revision of the polyethylene liner to a thicker size
. Open or arthroscopic popliteus tendon release
. Exchange of the femoral component
. Corticosteroid injection into the lateral collateral ligament

Correct Answer & Explanation

. Immediate revision to a constrained condylar knee

Explanation

Popliteus impingement or snapping over the lateral border of the femoral component can occur post-TKA, especially if the component is slightly oversized or laterally translated. If conservative measures fail, arthroscopic or open release of the popliteus tendon is an effective and definitive treatment.

Question 126

Topic: Total Knee Arthroplasty (TKA)

A patient complains of anterior knee pain and a sensation of patellar subluxation 1 year after a primary TKA. A computed tomography (CT) scan evaluates component rotation and demonstrates excessive internal rotation of the tibial component. What is the expected biomechanical consequence of a severely internally rotated tibial component on patellar tracking?

. Medialization of the tibial tubercle leading to lateral patellar tracking
. Lateralization of the tibial tubercle leading to medial patellar tracking
. Proximal patella alta
. Distal patella baja
. No significant effect on the Q-angle or patellar tracking

Correct Answer & Explanation

. Medialization of the tibial tubercle leading to lateral patellar tracking

Explanation

Internal rotation of the tibial component effectively medializes the tibial tubercle relative to the trochlear groove. This increases the dynamic Q-angle, resulting in increased lateral vector forces and subsequent lateral patellar tracking or subluxation.

Question 127

Topic: Total Knee Arthroplasty (TKA)
A 77-year-old man who underwent right total knee replacement surgery 2.5 years ago has had knee pain since surgery. The pain is diffuse, constant, and made worse with activity. He notes warmth and swelling in his knee. Examination shows a well-healed incision, no erythema, moderate warmth, synovitis, and an effusion. The knee is stable and has an arc of flexion between 3° and 120°. Radiographs show well-fixed and well-aligned implants. What is the most appropriate initial treatment?
. Knee aspiration for culture
. CT of the knee to assess implant rotation
. Indium-111 leukocyte/technetium-99m sulfur colloid scan of the knee
. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) laboratory studies

Correct Answer & Explanation

. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) laboratory studies

Explanation

DISCUSSION: This patient's history and physical findings are concerning for deep infection. Inflammatory markers, including ESR and CRP, should be obtained first. If the levels are elevated, knee aspiration should be performed for the synovial cell count and culture. A bone scan is not indicated in an initial investigation for deep infection; it is rarely helpful and is not cost-effective. CT to assess implant rotation is an appropriate investigation for knee pain when the clinical scenario is not suspicious for a deep infection and when infection has been excluded.

Question 128

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old female sustains a supracondylar distal femur fracture directly above a well-fixed total knee arthroplasty (TKA). The TKA is a posterior stabilized (PS) design. Which specific feature of the TKA component is the primary contraindication to utilizing a retrograde intramedullary nail for fracture fixation?

. Cruciate retaining polyethylene insert
. Closed box design of the femoral component
. Open box design of the femoral component
. Stemmed tibial component
. Excessive polyethylene thickness

Correct Answer & Explanation

. Cruciate retaining polyethylene insert

Explanation

A posterior stabilized (PS) TKA relies on a cam-and-post mechanism that requires an intercondylar 'box' on the femoral component. Some older or specific PS designs have a 'closed box' (a solid roof in the intercondylar notch), which physically prevents the passage of a retrograde intramedullary nail. An 'open box' PS design or a CR design typically allows nail passage.

Question 129

Topic: Total Knee Arthroplasty (TKA)

A 58-year-old patient suddenly develops cardiac arrest while undergoing a routine total knee arthoplasty. He is resuscitated with 20% lipid emulsion. What was the most likely causative agent for cardiac arrest?

. Epinephrine
. Bisoprolol
. Bupivacaine
. Fentanyl
. Rocuronium

Correct Answer & Explanation

. Epinephrine

Explanation

This patients cardiac arrest was likely caused by an intravascular bolus of Bupivacaine.Bupivacaine is a long acting local anesthetic. It acts on intracellular voltage-gated sodium channels to block sodium influx into nerve cells, which prevents depolarization. If administered systemically, bupivacaine can cause serious complications to the cardiovascular system. Side effects include hypotension, arrhythmia, bradycardia, heart block, and cardiac arrest. Treatment should involve urgent administration of intravascular lipid emulsion alongside standard ACLS protocols.Rosenblatt et al. describe the successful use of a 20% lipid emulsion to resuscitate a patient after a presumed bupivacaine-related cardiac arrest. Resuscitation involved a lipid emulsion bolus of 1 mL/kg given immediately, which was followed by a continuous infusion until the patient stabilized.Corman et al. evaluated the use of lipid emulsion for reversal of local anesthetic-induced toxicity. They suggest that lipid emulsion may reverse local anesthetic toxicity by extracting lipophilic local anesthetics from aqueous plasma or tissues or by counteracting local anesthetic inhibition of myocardial fatty acid oxygenation.Illustration A shows an ECG of a patient with clinical deterioration after systemic administration of bupivicaine. The ECG shows complete heart block with multifocal ventricular beats. The patient progressed to asystole.Inncorrect Answers:

Question 130

Topic: Total Knee Arthroplasty (TKA)
  • What is the most important surface geometry design parameter associated with decreased contact stress and wear reduction in total knee prostheses?
. Unrestrained roll-back
. Unrestrained rotational conformity
. Medial-Lateral conformity
. Anteroposterior conformity in flexion
. Anteroposterior conformity in extension

Correct Answer & Explanation

. Unrestrained roll-back

Explanation

The analysis of contact stress as a function of thickness of the polyethylene insert for tibial components has shown that a thickness of more than 8-10 millimeters should be maintained when possible. The contact stress in the tibial components was reduced most when the articulating surfaces were more conforming in the medial-lateral direction. Contact stresses were much less sensitive to changes in geometry in the anterior-posterior direction.

Question 131

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male with medial compartment osteoarthritis of the knee is being evaluated for a unicompartmental knee arthroplasty (UKA). Which of the following is historically and contemporarily considered an absolute contraindication to a medial UKA?

. Age less than 60 years
. Weight greater than 90 kg
. Anterior cruciate ligament (ACL) deficiency
. Flexion contracture of 10 degrees
. Inflammatory arthritis

Correct Answer & Explanation

. Age less than 60 years

Explanation

Inflammatory arthritis (such as Rheumatoid arthritis) is a universally accepted absolute contraindication to UKA because the disease is systemic and involves all compartments of the joint, leading to a very high rate of early failure. ACL deficiency was traditionally an absolute contraindication, but it is now considered a relative contraindication (or even acceptable in selected cases with fixed-bearing UKA). Age, weight, and mild flexion contractures (<15 degrees) are not absolute contraindications.

Question 132

Topic: Total Knee Arthroplasty (TKA)

Kinematic alignment in total knee arthroplasty aims to differ from traditional mechanical alignment primarily by doing which of the following?

. Cutting the proximal tibia strictly perpendicular to its mechanical axis
. Restoring the pre-arthritic joint lines and individualized native knee kinematics
. Deliberately over-correcting varus knees into 3 degrees of valgus
. Aligning the femoral component in 3 degrees of external rotation relative to the surgical epicondylar axis in all patients
. Using a constrained non-hinged insert in all primary cases

Correct Answer & Explanation

. Cutting the proximal tibia strictly perpendicular to its mechanical axis

Explanation

Kinematic alignment uses the patient's native, pre-arthritic articular geometry to guide bony resections. It aims to co-align the axes of the components with the three kinematic axes of the normal knee, rather than forcing a neutral mechanical axis.

Question 133

Topic: Total Knee Arthroplasty (TKA)
A 70-year-old woman has a 3-year history of gradually increasing diffuse and global right knee pain. Her main issues are difficulty with stairs, stiffness with prolonged sitting, and swelling. She has taken NSAIDs and has received intra-articular steroid injections, all with decreasing efficacy. Her right knee examination reveals a range of motion of 15° to 80° with a fixed deformity to varus and valgus stress. Her symptoms are no longer manageable nonsurgically. Radiographs reveal a 30-degree mechanical axis deformity. The deformity shown in the figure below is predominantly associated with:
. a hypoplastic lateral femoral condyle.
. a contracted medial collateral ligament.
. an excessive proximal tibial slope.
. trochlear dysplasia.

Correct Answer & Explanation

. a hypoplastic lateral femoral condyle.

Explanation

In the setting of valgus deformities, TKA poses different challenges than those encountered when varus deformities are present. Most valgus alignment is attributable to a deformity of the distal femur rather than of the proximal tibia. One of the major anatomical differences is a hypoplastic lateral femoral condyle which, when not recognized and used as a rotational reference point, can lead to internal rotation of the femoral component.

Question 134

Topic: Total Knee Arthroplasty (TKA)

During a total knee arthroplasty, which of the following component malpositions is most likely to result in lateral patellar tracking and potential subluxation?

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

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral component and internal rotation of the tibial component both increase the Q angle, leading to lateral patellar tracking and potential subluxation. Medialization of the femoral component and medialization of the patellar component also worsen lateral tracking.

Question 135

Topic: Total Knee Arthroplasty (TKA)

During a cruciate-retaining TKA, the surgeon notes that the knee is well balanced in extension but is tight in flexion, demonstrating restricted flexion and anterior liftoff of the tibial trial tray. Which of the following is the most appropriate next step to balance the knee?

. Recut the distal femur to remove more bone
. Upsize the femoral component
. Decrease the posterior slope of the tibial cut
. Release the posterior cruciate ligament
. Release the posterior capsule

Correct Answer & Explanation

. Release the posterior cruciate ligament

Explanation

A tight flexion gap with a balanced extension gap in a cruciate-retaining TKA, characterized by anterior liftoff of the tibial tray, is often caused by a tight posterior cruciate ligament (PCL). Releasing or recessing the PCL will increase the flexion gap without affecting the extension gap.

Question 136

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old man who underwent primary TKA 4 years ago presents with an inability to actively extend his knee following a fall. Clinical exam reveals a palpable gap at the superior pole of the patella. What is the most reliable surgical option for reconstruction of this chronic extensor mechanism disruption?

. Primary end-to-end repair with non-absorbable suture
. Primary repair augmented with semitendinosus autograft
. Extensor mechanism allograft or synthetic mesh reconstruction
. Gastrocnemius rotational flap
. Revision to a rotating hinge knee prosthesis

Correct Answer & Explanation

. Extensor mechanism allograft or synthetic mesh reconstruction

Explanation

Chronic or severe extensor mechanism disruptions in the setting of a TKA (especially large quadriceps defects or patellar tendon avulsions) have high failure rates with primary repair. Extensor mechanism allograft reconstruction or synthetic mesh reconstruction are the most reliable options to restore continuity.

Question 137

Topic: Total Knee Arthroplasty (TKA)



Which of the following is an absolute indication for using a rotating-hinge prosthesis rather than a constrained condylar knee (CCK) during a revision TKA?

. Attenuated posterior cruciate ligament
. Deficiency of the medial collateral ligament with a competent lateral collateral ligament
. Deficiency of both the medial collateral ligament and lateral collateral ligament
. Uncontained tibial metaphyseal bone loss
. Severe patellofemoral maltracking

Correct Answer & Explanation

. Deficiency of both the medial collateral ligament and lateral collateral ligament

Explanation

A constrained condylar knee (CCK) relies on the presence of at least one competent collateral ligament (typically the MCL) to function without early catastrophic failure. If both the MCL and LCL are deficient (global coronal instability), a rotating-hinge prosthesis is required.

Question 138

Topic: Total Knee Arthroplasty (TKA)



A patient develops severe true patella baja following a previous high tibial osteotomy and now requires a TKA. During the procedure, the patella cannot be safely everted. What is the most appropriate surgical maneuver to improve exposure and prevent patellar tendon avulsion?

. Tibial tubercle osteotomy
. Lateral retinacular release
. Medial epicondylar osteotomy
. V-Y quadricepsplasty
. Distal femoral shortening

Correct Answer & Explanation

. Tibial tubercle osteotomy

Explanation

True patella baja places the patellar tendon at high risk for avulsion during knee flexion and patellar eversion in TKA. A tibial tubercle osteotomy (TTO) provides excellent exposure, protects the tendon, and allows for proximal advancement of the tubercle to correct the baja during closure.

Question 139

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female presents with a painful catching sensation and an audible 'clunk' at 35 degrees of flexion as she extends her knee actively. She underwent a primary posterior-stabilized TKA 14 months ago. What is the underlying pathomechanics of this condition?

. Subluxation of the patella due to excessive internal rotation of the femoral component
. A fibrous nodule on the superior pole of the patella engaging the intercondylar box of the femur
. Overtightening of the posterior cruciate ligament during surgery
. Asymmetric wear of the polyethylene insert causing lateral compartment lift-off
. The popliteus tendon snapping over the edge of the lateral femoral condyle

Correct Answer & Explanation

. A fibrous nodule on the superior pole of the patella engaging the intercondylar box of the femur

Explanation

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibrous nodule forms on the undersurface of the quadriceps tendon and catches in the intercondylar notch of the femoral component during active extension.

Question 140

Topic: Total Knee Arthroplasty (TKA)

Which of the following best describes the primary objective of caliper-measured kinematic alignment in total knee arthroplasty?

. Restoring a neutral mechanical axis of the lower extremity to zero degrees
. Orienting the joint line precisely perpendicular to the mechanical axis of the tibia
. Co-aligning the components with the three kinematic axes of the native knee
. Maximizing external rotation of the femoral component to optimize patellar tracking
. Releasing ligaments extensively to achieve rectangular medial and lateral gaps

Correct Answer & Explanation

. Co-aligning the components with the three kinematic axes of the native knee

Explanation

Kinematic alignment aims to restore the patient's pre-arthritic native joint lines and alignment by co-aligning the implants with the three kinematic axes of the knee. This technique relies on measured resections matching implant thickness, rather than soft tissue releases to a neutral mechanical axis.

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