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Total Knee Arthroplasty (TKA) MCQs

Practice Set 12 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 221

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty utilizing a measured resection technique, the surgeon aims to establish a balanced rectangular flexion gap. If the femoral component is inadvertently placed in excessive internal rotation relative to the transepicondylar axis, what is the expected effect on the flexion gap?

. Tight medial in flexion, loose lateral in flexion
. Loose medial in flexion, tight lateral in flexion
. Tight medial in flexion, tight lateral in flexion
. Loose medial in flexion, loose lateral in flexion
. Symmetric tightening of both medial and lateral gaps

Correct Answer & Explanation

. Tight medial in flexion, loose lateral in flexion

Explanation

In measured resection TKA, placing the femoral component in internal rotation relative to the transepicondylar axis results in under-resection of the posterior medial femoral condyle and over-resection of the posterior lateral femoral condyle. The thicker retained bone on the medial side causes the medial flexion gap to be tight, while the lateral flexion gap becomes loose.

Question 222

Topic: Total Knee Arthroplasty (TKA)

A 72-year-old male with a history of a total knee arthroplasty (TKA) 5 years ago presents with a chronic, massive rupture of the patellar tendon following a fall. He is unable to perform a straight leg raise. According to recent literature, which of the following reconstructive techniques demonstrates the best long-term survivorship and prevention of extensor lag?

. Direct primary repair using heavy non-absorbable sutures
. Augmentation with an autologous semitendinosus graft
. Extensor mechanism allograft with a tibial bone block
. Reconstruction using a synthetic mesh (e.g., Marlex)
. Gastrocnemius rotational flap without tendon reconstruction

Correct Answer & Explanation

. Reconstruction using a synthetic mesh (e.g., Marlex)

Explanation

For chronic, massive extensor mechanism disruptions post-TKA, direct repair has a prohibitively high failure rate. Recent literature heavily supports the use of synthetic mesh (such as Marlex mesh) reconstruction over allograft tissue, demonstrating superior long-term durability, fewer infections, and less late stretching (extensor lag).

Question 223

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old woman complains of recurrent knee swelling and a sensation of her knee 'giving way' particularly when descending stairs, 1 year after a primary posterior-stabilized total knee arthroplasty. On examination, the knee is completely stable to varus and valgus stress in full extension. At 90 degrees of flexion, there is 12 mm of joint opening with both varus and valgus stress, and a positive anterior drawer test. Which intraoperative technical error most likely caused this specific complication?

. Excessive distal femoral resection
. Undersizing the femoral component
. Undersizing the tibial component
. Excessive proximal tibial resection
. Using a tibial insert that is too thick

Correct Answer & Explanation

. Undersizing the femoral component

Explanation

The patient presents with isolated flexion instability, characterized by a stable extension gap and a loose flexion gap. During a measured resection TKA, undersizing the femoral component in the anteroposterior (AP) dimension increases the flexion gap without altering the extension gap, leading to flexion instability. Excessive distal femoral resection would affect only the extension gap, causing extension instability. Excessive proximal tibial resection affects both gaps equally.

Question 224

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old man complains of persistent anterior knee pain and a feeling of instability 2 years after a primary TKA. CT scan evaluation demonstrates that the femoral component is internally rotated 6 degrees relative to the surgical transepicondylar axis, and the tibial component is internally rotated 9 degrees relative to the medial third of the tibial tubercle. What is the most likely clinical consequence of this combined component positioning?

. Lateral patellar maltracking and anterior knee pain
. Medial patellar subluxation
. Excessive tightness of the flexion gap
. Isolated mid-flexion instability
. Posterior cruciate ligament rupture

Correct Answer & Explanation

. Lateral patellar maltracking and anterior knee pain

Explanation

Internal rotation of the femoral component medially translates the trochlear groove, and internal rotation of the tibial component externalizes the tibial tubercle. Both errors functionally increase the Q-angle effect, pulling the extensor mechanism laterally. This combined malrotation predictably leads to lateral patellar maltracking, subluxation, and severe anterior knee pain.

Question 225

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old man presents with anterior knee pain and a feeling of instability when descending stairs, 1 year after a posterior-stabilized total knee arthroplasty (TKA). Radiographs demonstrate that the femoral component was placed in excessive internal rotation. What is the primary kinematic consequence of this specific component malposition?

. Medial-lateral instability in full extension
. Lateral patellar tracking and patellofemoral instability
. Increased lateral flexion gap resulting in mid-flexion instability
. Patella baja due to altered joint line height
. Excessive external rotation of the tibia during the swing phase of gait

Correct Answer & Explanation

. Lateral patellar tracking and patellofemoral instability

Explanation

Internal rotation of the femoral component in TKA effectively medializes the trochlear groove relative to the extensor mechanism, which increases the Q-angle. This alteration leads to lateral patellar tracking, anterior knee pain, and potential patellar subluxation or dislocation. It also abnormally tightens the medial flexion gap while loosening the lateral flexion gap, creating asymmetric kinematics during flexion, rather than extension instability.

Question 226

Topic: Total Knee Arthroplasty (TKA)

In kinematic alignment for a total knee arthroplasty, the surgical goal differs from traditional mechanical alignment by aiming to restore the patient's pre-arthritic joint lines. This approach typically results in which of the following component positions compared to mechanical alignment?

. More valgus femoral component and more varus tibial component
. More varus femoral component and more valgus tibial component
. Parallel joint line to the mechanical axis
. Increased external rotation of the femoral component
. Symmetrical extension gap

Correct Answer & Explanation

. More valgus femoral component and more varus tibial component

Explanation

Kinematic alignment aims to restore the native joint line, which typically involves placing the femoral component in slightly more valgus and the tibial component in slightly more varus compared to the neutral mechanical axis.

Question 227

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old man is 3 weeks status post primary TKA and presents with a 4-day history of increasing knee pain, erythema, and a temperature of 38.5 C. Joint aspiration yields purulent fluid. Which of the following is the most appropriate indication for proceeding with Debridement, Antibiotics, and Implant Retention (DAIR)?

. Presence of a draining sinus tract
. Symptoms lasting longer than 4 weeks
. Well-fixed components with acute symptom onset (< 3 weeks post-op)
. Infection with Methicillin-resistant Staphylococcus aureus
. Loosening of the tibial component on radiographs

Correct Answer & Explanation

. Well-fixed components with acute symptom onset (< 3 weeks post-op)

Explanation

DAIR is indicated for early postoperative infections (typically within 4 weeks of surgery) or acute hematogenous infections with symptom duration of less than 3 weeks, provided the implants are stable and the soft tissue envelope is intact.

Question 228

Topic: Total Knee Arthroplasty (TKA)

A patient complains of anterior knee pain and a "clunking" sensation 6 months following a primary TKA. Examination shows lateral patellar subluxation in early flexion. Which component malposition is most likely responsible for this finding?

. External rotation of the femoral component
. Internal rotation of the femoral or tibial components
. Excessive posterior slope of the tibial tray
. Valgus placement of the tibial tray
. Lateralization of the femoral component

Correct Answer & Explanation

. Internal rotation of the femoral or tibial components

Explanation

Internal rotation of either the femoral or tibial components increases the Q-angle, which pulls the extensor mechanism laterally. This leads to lateral patellar maltracking, subluxation, and anterior knee pain.

Question 229

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old woman is 1-year post-posterior stabilized TKA. She complains of a painful catching and popping sensation in her anterior knee as she actively extends her knee from a flexed position. What implant design factor most significantly contributes to this specific complication?

. Highly cross-linked polyethylene insert
. Short patellar tendon length
. Intercondylar box design with a sharp, abrupt superior edge
. Excessive posterior slope of the tibial tray
. Under-resection of the distal femur

Correct Answer & Explanation

. Intercondylar box design with a sharp, abrupt superior edge

Explanation

Patellar clunk syndrome occurs in posterior-stabilized knees when a fibrotic nodule forms at the superior pole of the patella and catches in the intercondylar notch. A high intercondylar box ratio and sharp superior box edges increase this risk.

Question 230

Topic: Total Knee Arthroplasty (TKA)

During a primary TKA utilizing a gap balancing technique, the surgeon finds that the extension gap is perfectly symmetric and rectangular. However, the flexion gap is tight medially and loose laterally. What is the most appropriate adjustment to the femoral component to balance the flexion gap?

. Internally rotate the femoral component
. Externally rotate the femoral component
. Downsize the femoral component
. Upsize the femoral component
. Recut the proximal tibia with more posterior slope

Correct Answer & Explanation

. Externally rotate the femoral component

Explanation

External rotation of the femoral component relative to the posterior condylar axis removes more bone from the posteromedial condyle and less from the posterolateral condyle. This opens the medial flexion space and tightens the lateral flexion space, balancing the gap.

Question 231

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old woman undergoes a primary TKA for an end-stage 25-degree valgus knee deformity. In the PACU, she has a complete foot drop and sensory loss over the dorsum of the foot. Pulses are symmetric and palpable. What is the immediate recommended management?

. Immediate surgical exploration and neurolysis of the peroneal nerve
. Removal of restrictive dressings and flexion of the knee to 20-30 degrees
. Application of a rigid cast in full extension to prevent contracture
. Immediate revision to a hinged knee prosthesis
. Obtain an emergent MRI of the lumbar spine

Correct Answer & Explanation

. Removal of restrictive dressings and flexion of the knee to 20-30 degrees

Explanation

Peroneal nerve palsy post-valgus TKA is typically a stretch neuropraxia resulting from deformity correction. Initial management includes releasing tight dressings and flexing the knee to 20-30 degrees to relieve tension on the nerve.

Question 232

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female undergoes TKA for severe valgus osteoarthritis using a measured resection technique. After the distal femoral and proximal tibial cuts are made, the extension gap is rectangular. In flexion, the gap is asymmetric, being significantly tighter laterally than medially. Which of the following technical errors most likely occurred?

. Internal rotation of the femoral component
. External rotation of the femoral component
. Excessive valgus of the distal femoral cut
. Insufficient valgus of the distal femoral cut
. Excessive posterior slope of the tibial cut

Correct Answer & Explanation

. Internal rotation of the femoral component

Explanation

Internal rotation of the femoral component moves the posterior lateral condyle relatively more distal/posterior, which decreases the size of the lateral flexion gap. In valgus knees, the lateral femoral condyle is often hypoplastic. If the surgeon sets femoral rotation at a standard 3 degrees of external rotation off the posterior condylar axis without accounting for this hypoplasia, it effectively leads to internal rotation of the femoral component relative to the surgical transepicondylar axis, resulting in a tight lateral flexion gap.

Question 233

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female undergoes a right TKA for severe valgus osteoarthritis with a 20-degree valgus deformity and a 15-degree flexion contracture. Postoperatively in the recovery room, she is noted to have a dense foot drop and numbness over the dorsum of her right foot. Which of the following is the most appropriate initial management?

. Immediate surgical exploration of the peroneal nerve
. Magnetic resonance imaging (MRI) of the lumbar spine
. Removal of all compressive dressings and slight flexion of the knee
. Application of an ankle-foot orthosis and routine discharge
. Electromyography (EMG) of the lower extremity

Correct Answer & Explanation

. Removal of all compressive dressings and slight flexion of the knee

Explanation

Peroneal nerve palsy is a dreaded complication following TKA for severe valgus and flexion deformities. It occurs due to traction/stretching of the nerve as the contracted lateral structures are corrected into extension and neutral alignment. The most critical initial step is to remove all compressive dressings (e.g., ACE wraps, continuous passive motion straps) and slightly flex the knee to relieve mechanical tension on the nerve. Immediate exploration is rarely indicated. EMG is useful only after 3 to 6 weeks if symptoms do not improve.

Question 234

Topic: Total Knee Arthroplasty (TKA)

During a total knee arthroplasty, the surgeon inadvertently places the femoral component in excessive internal rotation relative to the epicondylar axis. Which of the following biomechanical consequences is most likely to occur?

. Lateral patellar tracking and medial compartment tightness in flexion
. Lateral patellar tracking and lateral compartment tightness in flexion
. Medial patellar tracking and medial compartment tightness in flexion
. Medial patellar tracking and lateral compartment tightness in flexion
. Global symmetrical instability in both flexion and extension

Correct Answer & Explanation

. Lateral patellar tracking and lateral compartment tightness in flexion

Explanation

Internal rotation of the femoral component in a TKA has two primary negative effects. First, it medializes the femoral trochlear groove, which effectively increases the Q-angle and leads to lateral patellar maltracking. Second, it shifts the posterior medial condyle distally/posteriorly relative to the lateral condyle, resulting in a tight medial flexion gap and a loose lateral flexion gap.

Question 235

Topic: Total Knee Arthroplasty (TKA)

Following the implantation of trial components during a TKA, the surgeon notices that the patella tends to tilt and subluxate laterally during knee flexion. Which of the following adjustments to the components would exacerbate this problem?

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

Correct Answer & Explanation

. Internal rotation of the tibial component

Explanation

Lateral patellar subluxation is caused by an increased Q-angle or component malrotation. Internal rotation of the tibial component lateralizes the tibial tubercle relative to the femur, increasing the Q-angle and exacerbating lateral patellar tracking. External rotation of the femoral and tibial components, and medialization of the patellar button generally improve patellar tracking.

Question 236

Topic: Total Knee Arthroplasty (TKA)

A 62-year-old man who underwent a posterior-stabilized TKA 9 months ago presents with an anterior knee catch and an audible 'clunk' when extending his knee actively from 45 degrees of flexion to full extension. What is the primary pathophysiologic mechanism of this complication?

. Patellar component loosening
. Oversized patellar button
. Fibrous nodule entrapment in the femoral intercondylar notch
. Impingement of the patella on the anterior tibial post
. Over-resection of the anterior femoral condyle

Correct Answer & Explanation

. Fibrous nodule entrapment in the femoral intercondylar notch

Explanation

Patellar clunk syndrome typically occurs after posterior-stabilized TKA and is caused by the formation of a fibrosynovial nodule at the superior pole of the patella. During knee flexion, the nodule engages the intercondylar box of the femoral component. As the knee extends, the nodule forcibly pops out of the box (typically between 30 to 45 degrees of flexion), producing a palpable and audible clunk.

Question 237

Topic: Total Knee Arthroplasty (TKA)

A 78-year-old man presents with knee pain and swelling 15 years after a primary TKA. Radiographs show significant eccentric wear of the polyethylene bearing. Intraoperatively, the polyethylene insert exhibits large flakes of material separated from the articular surface. Which wear mechanism is primarily responsible for this appearance?

. Abrasive wear
. Delamination wear
. Adhesive wear
. Third-body wear
. Burnishing

Correct Answer & Explanation

. Delamination wear

Explanation

Delamination wear is characterized by large flakes of polyethylene separating from the articular surface. This is caused by subsurface fatigue due to cyclic loading and is historically associated with oxidation of the polyethylene (often seen in legacy gamma-irradiated-in-air polyethylene components). Abrasive wear involves scratching, while adhesive wear involves microscopic transfer of polyethylene to the metal surface.

Question 238

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female undergoes total knee arthroplasty utilizing a posterior stabilized (PS) implant. During trial range of motion, the surgeon notes that the tibial post impinges on the anterior aspect of the femoral cam/box when the knee is brought into full extension. What is the most appropriate intraoperative step to correct this?

. Upsize the femoral component
. Downsize the femoral component
. Increase the posterior slope of the tibial cut
. Decrease the posterior slope of the tibial cut
. Recut the distal femur to add more valgus

Correct Answer & Explanation

. Decrease the posterior slope of the tibial cut

Explanation

Anterior impingement of the tibial post on the femoral box or cam in full extension with a posterior stabilized TKA is typically caused by excessive posterior tibial slope. Excessive slope effectively pitches the tibial post forward relative to the femur when the knee extends. Decreasing the posterior slope of the tibial cut or using an insert that corrects this will resolve the impingement.

Question 239

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old patient presents 6 weeks after a primary total knee arthroplasty with complaints of stiffness. Her range of motion is 15 degrees to 75 degrees. Radiographs demonstrate that the prosthetic joint line is elevated by 8 mm compared to her preoperative films. Which of the following intraoperative technical errors is the most likely cause of this elevated joint line?

. Over-resection of the distal femur and under-resection of the proximal tibia
. Under-resection of the distal femur and over-resection of the proximal tibia
. Excessive external rotation of the femoral component
. Undersizing the femoral component in the anteroposterior dimension
. Oversizing the femoral component in the anteroposterior dimension

Correct Answer & Explanation

. Over-resection of the distal femur and under-resection of the proximal tibia

Explanation

Joint line elevation in TKA commonly occurs when the surgeon over-resects the distal femur. This widens the extension gap. To achieve stability in extension, the surgeon is then forced to use a thicker polyethylene insert. The combination of a resected distal femur and a thicker poly insert pushes the entire tibiofemoral articulation proximally, elevating the joint line. Under-resecting the proximal tibia further contributes to joint line elevation by failing to lower the base upon which the thick insert sits.

Question 240

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old male presents with a feeling of 'giving way' when descending stairs 1 year after a primary TKA. On examination, the knee is well-aligned, fully extends, and flexes to 125 degrees. There is a 2 mm symmetric opening to varus and valgus stress in extension. However, at 90 degrees of flexion, there is marked anterior-posterior translation and 6 mm of opening to varus and valgus stress. Which of the following surgical errors most likely contributed to this presentation?

. Undersizing the femoral component in the anteroposterior dimension
. Excessive distal femoral resection
. Excessive posterior tibial slope
. Oversizing the femoral component
. Inadequate posterior condylar offset restoration

Correct Answer & Explanation

. Undersizing the femoral component in the anteroposterior dimension

Explanation

The patient is experiencing flexion instability, characterized by a balanced extension gap but a loose flexion gap. Undersizing the femoral component in the anteroposterior (AP) dimension (especially when using anterior referencing, which resects more posterior condyle) increases the flexion gap without affecting the extension gap, leading to isolated flexion instability.

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