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Total Knee Arthroplasty (TKA) MCQs

Practice Set 22 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 421

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty (TKA), the surgeon checks the gap balancing with spacer blocks. The extension gap is symmetric and rectangular, allowing appropriate tension. However, the flexion gap is tight and symmetric. Which of the following is the most appropriate next step to balance the knee?

. Release the posterior cruciate ligament (if retaining) or downsize the femoral component.
. Resect more distal femur.
. Increase the posterior slope of the tibial cut.
. Release the medial collateral ligament.
. Upsize the femoral component.

Correct Answer & Explanation

. Release the posterior cruciate ligament (if retaining) or downsize the femoral component.

Explanation

A tight flexion gap with a balanced extension gap implies that the anteroposterior dimension of the femoral component is too large, or the posterior soft tissues are too tight. The appropriate surgical options include releasing the PCL (if it is a cruciate-retaining knee), down-sizing the femoral component (which removes more posterior condylar bone and opens the flexion gap), or translating the femoral component anteriorly. Resecting more distal femur would affect the extension gap. Increasing the posterior tibial slope affects both gaps but preferentially opens the flexion gap; however, changing the femoral component size or PCL release are the primary direct corrections.

Question 422

Topic: Total Knee Arthroplasty (TKA)

A surgeon is performing a total knee arthroplasty (TKA). After making the initial bone cuts and inserting trial components, she notes that the knee is tight in extension (with a lack of full extension) but perfectly balanced in 90 degrees of flexion. What is the most appropriate next step to balance the knee?

. Downsize the femoral component
. Increase the posterior slope of the tibial cut
. Resect more bone from the distal femur
. Resect more bone from the proximal tibia
. Release the posterior cruciate ligament (PCL)

Correct Answer & Explanation

. Resect more bone from the distal femur

Explanation

In TKA gap balancing, if the extension gap is tight (knee lacks full extension) but the flexion gap is well-balanced, the appropriate step is to resect more bone from the distal femur. Distal femoral resection increases the extension gap without affecting the flexion gap. Resecting more proximal tibia would erroneously increase both the flexion and extension gaps. Downsizing the femoral component increases the flexion gap.

Question 423

Topic: Total Knee Arthroplasty (TKA)

During a Total Knee Arthroplasty (TKA), trial components are inserted. The surgeon notes that the extension gap is excessively tight, but the flexion gap is perfectly balanced and stable. Which of the following is the most appropriate next step to correct the gap kinematics?

. Resect more proximal tibia
. Resect more distal femur
. Decrease the femoral component size
. Recut the posterior femoral condyles
. Release the posterior cruciate ligament

Correct Answer & Explanation

. Resect more distal femur

Explanation

In gap balancing for TKA, if the extension gap is tight but the flexion gap is balanced, the surgeon must address a structure that only affects extension. Resecting more distal femur will increase the extension gap without affecting the flexion gap. Resecting more proximal tibia would increase both gaps symmetrically. Decreasing the femoral component size would increase the flexion gap.

Question 424

Topic: Total Knee Arthroplasty (TKA)

During a total knee arthroplasty (TKA), the surgeon inadvertently internally rotates the femoral component relative to the surgical epicondylar axis. What is the most likely biomechanical consequence of this technical error?

. Medial patellar subluxation
. Lateral patellar tracking and potential dislocation
. Increased flexion gap laxity medially
. Decreased extension gap
. Symmetric tightness in both medial and lateral compartments in flexion

Correct Answer & Explanation

. Lateral patellar tracking and potential dislocation

Explanation

Internal rotation of the femoral component in TKA mediatizes the trochlear groove, thereby increasing the Q angle. This leads to lateral patellar tracking, tilt, and an increased risk of lateral patellar subluxation or dislocation. It also creates a tight medial flexion gap.

Question 425

Topic: Total Knee Arthroplasty (TKA)

In an orthopedic clinical trial comparing two types of total knee implants, the researchers want to ensure they have an 80% probability of detecting a true clinical difference if one actually exists. This probability represents which of the following statistical concepts?

. Type I error (alpha)
. Type II error (beta)
. Statistical power (1 - beta)
. Positive predictive value
. Confidence interval

Correct Answer & Explanation

. Statistical power (1 - beta)

Explanation

Statistical power is defined as 1 - beta, which is the probability of correctly rejecting the null hypothesis when it is false (i.e., finding a true difference). A power of 0.80 (80%) is generally considered the standard benchmark for a well-designed clinical trial.

Question 426

Topic: Total Knee Arthroplasty (TKA)

During a primary total knee arthroplasty, the surgeon uses a measured resection and gap balancing technique. With the trial components in place, the knee is found to be tight in flexion but perfectly balanced in extension. Which of the following surgical adjustments will best correct this specific mismatch?

. Resect more distal femur
. Decrease the posterior slope of the tibial cut
. Downsize the femoral component
. Release the posterior cruciate ligament
. Upsize the tibial polyethylene insert

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is tight in flexion and balanced in extension has an isolated tight flexion gap. This can be corrected by downsizing the femoral component, which decreases the anteroposterior dimension, or by increasing the posterior tibial slope.

Question 427

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old patient presents with end-stage knee osteoarthritis and a 25-degree extra-articular diaphyseal varus deformity of the femur. What is the most appropriate management?

. TKA with standard intra-articular resection
. TKA with constrained condylar knee (CCK)
. Staged or simultaneous extra-articular femoral osteotomy and TKA
. Unicompartmental knee arthroplasty
. TKA with hinged prosthesis

Correct Answer & Explanation

. Staged or simultaneous extra-articular femoral osteotomy and TKA

Explanation

Extra-articular deformities greater than 20 degrees in the coronal plane typically require an extra-articular osteotomy to properly restore the mechanical axis. Standard intra-articular cuts for such large deformities compromise collateral ligament attachments and destabilize the knee.

Question 428

Topic: Total Knee Arthroplasty (TKA)



A patient with a significant post-traumatic valgus deformity of the proximal tibia is undergoing a primary TKA. Through a standard medial parapatellar arthrotomy, which structure is most commonly released first to balance the fixed valgus knee?

. Superficial medial collateral ligament
. Deep medial collateral ligament
. Posteromedial corner
. Iliotibial band and posterolateral capsule
. Patellar tendon

Correct Answer & Explanation

. Iliotibial band and posterolateral capsule

Explanation

In a fixed valgus knee, the lateral side is tight. Soft tissue balancing requires a sequential release of the tight lateral structures, most commonly starting with the iliotibial band and posterolateral capsule, followed by the popliteus and LCL if needed.

Question 429

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old patient with a 25-degree coronal plane extra-articular bowing deformity of the midshaft femur presents for a Total Knee Arthroplasty. Which of the following is the most appropriate management?

. Standard TKA with an intra-articular constrained hinge
. Standard TKA with aggressive soft tissue release
. Simultaneous or staged femoral osteotomy and TKA
. TKA using a customized patient-specific cutting block for an intra-articular cut
. TKA with a lateral opening wedge osteotomy at the joint line

Correct Answer & Explanation

. Simultaneous or staged femoral osteotomy and TKA

Explanation

For extra-articular deformities >20 degrees in the coronal plane, intra-articular compensatory bone cuts will compromise collateral ligament attachments. A staged or simultaneous extra-articular osteotomy is indicated.

Question 430

Topic: Total Knee Arthroplasty (TKA)

A 17-year-old female soccer player sustains a non-contact anterior cruciate ligament (ACL) tear. Compared to her male counterparts, she is at a substantially higher risk for this injury. Which of the following biomechanical or anatomic risk factors is most strongly associated with this increased risk in females?

. Increased intercondylar notch width
. Decreased Q angle
. Neuromuscular imbalances characterized by quadriceps dominance
. Decreased posterior tibial slope
. Hypertrophy of the semitendinosus muscle

Correct Answer & Explanation

. Neuromuscular imbalances characterized by quadriceps dominance

Explanation

Female athletes face a higher risk of non-contact ACL tears largely due to neuromuscular factors, particularly "quadriceps dominance" and weaker hamstring co-contraction. Additionally, females generally possess a narrower intercondylar notch, increased Q angle, and increased dynamic valgus loading.

Question 431

Topic: Total Knee Arthroplasty (TKA)

In the standard evaluation of normal lower extremity mechanical alignment using a full-length standing anteroposterior radiograph, what are the normal ranges for the mechanical lateral distal femoral angle (mLDFA) and the mechanical medial proximal tibial angle (mMPTA)?

. mLDFA 80-84 degrees; mMPTA 90-95 degrees
. mLDFA 85-90 degrees; mMPTA 85-90 degrees
. mLDFA 90-95 degrees; mMPTA 80-84 degrees
. mLDFA 95-100 degrees; mMPTA 95-100 degrees
. mLDFA 85-90 degrees; mMPTA 95-100 degrees

Correct Answer & Explanation

. mLDFA 85-90 degrees; mMPTA 85-90 degrees

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90), and the normal mMPTA is also approximately 87 degrees (range 85-90). This combined anatomy keeps the knee joint line horizontal to the ground during normal single-leg stance.

Question 432

Topic: Total Knee Arthroplasty (TKA)

A patient with a remote midshaft femur fracture malunion presents for TKA. Preoperative planning reveals a coronal plane extra-articular deformity. What is the generally accepted threshold for femoral extra-articular coronal deformity beyond which a concurrent osteotomy should be considered rather than an intra-articular compensatory resection?

. 5 degrees
. 10 degrees
. 20 degrees
. 30 degrees
. Intra-articular correction is always preferred regardless of angle

Correct Answer & Explanation

. 20 degrees

Explanation

Intra-articular compensatory bone cuts in TKA are generally safe for extra-articular femoral deformities up to 20 degrees in the coronal plane. Deformities exceeding this typically require concurrent or staged extra-articular osteotomy to avoid excessive ligamentous imbalance.

Question 433

Topic: Total Knee Arthroplasty (TKA)

Elevation of the joint line during a revision TKA most commonly leads to which of the following postoperative complications?

. Mid-flexion instability
. Patella alta
. Hyperextension recurvatum
. Excessive femoral rollback
. Medial collateral ligament attenuation

Correct Answer & Explanation

. Mid-flexion instability

Explanation

Elevating the joint line alters the kinematics of the knee by moving the femoral origin of the collateral ligaments distally relative to the joint line. This mismatch often results in laxity in mid-flexion (mid-flexion instability) and can cause an apparent patella baja.

Question 434

Topic: Total Knee Arthroplasty (TKA)

Which of the following design modifications in a posterior-stabilized TKA helps substitute for the function of the resected posterior cruciate ligament (PCL)?

. Highly cross-linked polyethylene
. An anterior cam on the tibial polyethylene insert
. A femoral cam and tibial post mechanism
. Symmetric condylar geometry
. Increased anterior flange height

Correct Answer & Explanation

. A femoral cam and tibial post mechanism

Explanation

In a posterior-stabilized TKA, the PCL is excised. A central post on the tibial polyethylene insert engages a cam on the femoral component during flexion, physically forcing femoral rollback and preventing anterior subluxation of the femur.

Question 435

Topic: Total Knee Arthroplasty (TKA)

When planning a primary TKA for a patient with an extra-articular valgus tibial deformity, intra-articular resection is typically considered acceptable if the deformity is within what angular limit in the coronal plane?

. 5 degrees
. 10 degrees
. 20 degrees
. 30 degrees
. 45 degrees

Correct Answer & Explanation

. 10 degrees

Explanation

Intra-articular bone cuts can safely compensate for up to 10 to 15 degrees of extra-articular coronal plane deformity in the tibia. Deformities greater than 10-15 degrees risk compromising the tibial attachment of the collateral ligaments, usually necessitating an extra-articular osteotomy.

Question 436

Topic: Total Knee Arthroplasty (TKA)

During trial reduction in a cruciate-retaining TKA, the knee is perfectly balanced in full extension but significantly tight in flexion. Which of the following is the most appropriate surgical step to balance the knee?

. Resect more distal femur
. Downsize the femoral component
. Upsize the femoral component
. Use a thicker polyethylene insert
. Decrease the posterior tibial slope

Correct Answer & Explanation

. Downsize the femoral component

Explanation

A knee that is balanced in extension but tight in flexion has an isolated tight flexion gap. Downsizing the femoral component (using an anterior referencing system) reduces the posterior condylar offset, increasing the flexion gap without altering the extension gap.

Question 437

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 438

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 439

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 440

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.

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