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Total Knee Arthroplasty (TKA) MCQs

Practice Set 3 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 41

Topic: Total Knee Arthroplasty (TKA)

A patient complains of the knee 'giving way' when rising from a chair and descending stairs 2 years after a primary TKA. Examination shows laxity to varus and valgus stress at 90 degrees of flexion, but stability in full extension. Which complication has occurred?

. Global instability
. Extension gap instability
. Flexion gap instability
. Genu recurvatum
. Patellofemoral maltracking

Correct Answer & Explanation

. Flexion gap instability

Explanation

Flexion gap instability presents with a knee that is stable in extension but unstable in flexion. It is often caused by undersizing the femoral component in the A-P plane, excessive posterior slope of the tibial cut, or late PCL failure in a cruciate-retaining knee.

Question 42

Topic: Total Knee Arthroplasty (TKA)

During a revision TKA, the original epicondylar axis is obscured by massive bone loss. Which of the following secondary landmarks is most reliable for establishing proper femoral component rotation?

. Whiteside's line (anteroposterior axis)
. Posterior condylar axis
. Tibial tubercle
. Linea aspera (posterior femoral shaft)
. Medial collateral ligament origin

Correct Answer & Explanation

. Linea aspera (posterior femoral shaft)

Explanation

In revision TKA where the epicondyles and trochlear groove are absent, the linea aspera of the femur is a reliable landmark. It can be used to set stem version, which consequently guides the rotational alignment of the femoral component.

Question 43

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female presents with a loose TKA. Preoperative planning indicates severe cavitary and segmental bone loss of the proximal tibia with compromised metaphyseal cancellous bone, but an intact diaphyseal isthmus (AORI Type 2B/3).

Which of the following is the most biomechanically sound fixation method for the tibial component?

. Standard primary baseplate with a thick cement mantle
. Tantalum metaphyseal cone with a diaphyseal engaging stem
. Impaction bone grafting with a short unstemmed baseplate
. Allograft-prosthetic composite without diaphyseal fixation
. Fully cemented short stem component

Correct Answer & Explanation

. Tantalum metaphyseal cone with a diaphyseal engaging stem

Explanation

For severe metaphyseal bone loss (AORI Type 2B or 3), highly porous tantalum cones or titanium sleeves combined with diaphyseal engaging stems provide excellent initial mechanical stability and allow for biologic ingrowth. Cement alone or short stems are insufficient for massive defects.

Question 44

Topic: Total Knee Arthroplasty (TKA)

During a complex revision TKA, the surgeon encounters severe extensor mechanism tightness preventing adequate exposure and eversion of the patella. A tibial tubercle osteotomy (TTO) is chosen. Which of the following is a critical technical aspect of performing this TTO?

. Creating a distal bevel to prevent stress risers
. Leaving a medial soft tissue hinge to protect the anterior tibial artery
. Limiting the length of the osteotomy to 2-3 cm
. Placing the osteotomy strictly lateral to the tibial crest
. Reattaching the fragment with non-absorbable sutures only

Correct Answer & Explanation

. Creating a distal bevel to prevent stress risers

Explanation

A TTO for TKA exposure should be approximately 6-8 cm long, maintain a lateral soft-tissue hinge, and crucially include a distal bevel. The distal bevel prevents the creation of a sharp cortical stress riser, reducing the risk of postoperative tibial shaft fractures.

Question 45

Topic: Total Knee Arthroplasty (TKA)

During intraoperative gap balancing in a revision TKA, the surgeon notes that the joint is stable in extension but exhibits symmetric, excessive laxity in flexion.

Which of the following is the most appropriate corrective action?

. Downsize the femoral component
. Increase the size of the femoral component and use posterior augments
. Use a thicker tibial polyethylene insert
. Apply distal femoral augments
. Release the posterior cruciate ligament

Correct Answer & Explanation

. Increase the size of the femoral component and use posterior augments

Explanation

Symmetric flexion instability with a stable extension gap is corrected by increasing the anteroposterior (AP) dimension of the femur. This is achieved by upsizing the femoral component and utilizing posterior augments to tighten the flexion gap without affecting the extension gap.

Question 46

Topic: Total Knee Arthroplasty (TKA)

Intraoperative assessment during a revision TKA demonstrates symmetrical tightness in both the flexion and extension gaps. The current polyethylene insert is a standard 10 mm thickness. What is the most appropriate next step to balance the knee?

. Upsize the femoral component
. Apply posterior femoral augments
. Resect additional posterior femoral condyle
. Resect additional proximal tibia or use a thinner polyethylene insert
. Perform a fractional lengthening of the medial collateral ligament

Correct Answer & Explanation

. Resect additional proximal tibia or use a thinner polyethylene insert

Explanation

Symmetrical tightness in both flexion and extension gaps indicates that the overall joint space is too small. The correct management is to increase both gaps equally by either using a thinner polyethylene insert (if available) or resecting additional proximal tibia.

Question 47

Topic: Total Knee Arthroplasty (TKA)

Which of the following statements best encapsulates the ultimate goal of Paley's geometric principles in lower extremity deformity correction?

. To achieve maximal limb lengthening, regardless of angular correction.
. To simplify surgical techniques by avoiding complex geometric calculations.
. To restore normal mechanical alignment and joint orientation through meticulous, mathematically sound preoperative planning.
. To primarily address intra-articular deformities, leaving extra-articular issues for secondary procedures.
. To ensure that all osteotomies are performed acutely to minimize patient discomfort.

Correct Answer & Explanation

. To restore normal mechanical alignment and joint orientation through meticulous, mathematically sound preoperative planning.

Explanation

Correct Answer: CThe introductory and foundational geometry sections of the text repeatedly emphasize this core objective. The text states: 'The ultimate goal of any deformity correction is the restoration of normal mechanical alignment and joint orientation through meticulous, mathematically sound preoperative planning.' It also highlights that 'a deep, intuitive understanding of these principles is not just beneficialโ€”it is an absolute clinical mandate.'Option A is incorrect as lengthening is one aspect, but not the sole or ultimate goal, and it must be coupled with angular correction. Option B is incorrect; Paley's principles are highly geometric and require complex calculations, though they simplify theoutcomeby making it predictable. Option D is incorrect as the principles address both intra- and extra-articular deformities (e.g., Rule Two for intra-articular CORAs). Option E is incorrect as both acute and gradual corrections are discussed, and the timing of correction is not the ultimate goal of the geometric principles themselves.

Question 48

Topic: Total Knee Arthroplasty (TKA)

A 25-year-old patient requires a distal femoral osteotomy for a severe valgus deformity. Preoperative planning indicates that the Center of Rotation of Angulation (CORA) is located very close to the knee joint line, making an osteotomy at this precise location technically challenging and potentially compromising joint integrity. The surgeon decides to perform the osteotomy slightly proximal to the CORA, while still ensuring the hinge axis of the temporary external fixator passes through the CORA. According to Paley's Three Laws of Osteotomy, what is the expected outcome of this approach?

. Pure angular correction without any translation.
. Angulation with intentional translation, but correct mechanical axis alignment.
. Iatrogenic translation deformity with misaligned mechanical axes.
. Significant limb lengthening due to the proximal osteotomy.
. Significant limb shortening due to the proximal osteotomy.

Correct Answer & Explanation

. Angulation with intentional translation, but correct mechanical axis alignment.

Explanation

Correct Answer: BThis scenario describes Paley's Osteotomy Rule Two: 'When the hinge axis passes through the CORA, but the osteotomy is performed at a different level (proximal or distal to the CORA), the correction results in angulation plus translation.' The mechanical axes will still align correctly at the end of the procedure, but the bone ends at the actual osteotomy site will be offset (displaced). This rule is a powerful tool when the CORA is in an undesirable location, allowing the surgeon to achieve overall mechanical alignment while accepting an intentional offset at the osteotomy site.Option A is incorrect:Pure angular correction (Rule One) occurs only when both the osteotomy and the hinge axis pass directly through the CORA.Option C is incorrect:Iatrogenic translation deformity (Rule Three) occurs when both the hinge axis and the osteotomy are separate from the CORA, leading to misaligned mechanical axes. In this case, the hinge axis still passes through the CORA, ensuring mechanical axis alignment.Options D and E are incorrect:While some minor length changes can occur, the primary outcome described by Rule Two is angulation with translation, not significant lengthening or shortening as the main feature.

Question 49

Topic: Total Knee Arthroplasty (TKA)

A 50-year-old patient undergoes a distal femoral extension osteotomy to correct a significant procurvatum deformity. Postoperatively, the patient's mechanical alignment is restored, but they complain of a new-onset, significant limitation in knee flexion. What is the primary biomechanical reason for this?

. The osteotomy moved the functional arc of motion entirely into extension
. Iatrogenic patella alta reduced quadriceps efficiency
. The patellofemoral joint pressure was abnormally reduced
. The posterior cruciate ligament was inadvertently lengthened
. A sympathetic reflex arc inhibited the hamstring muscles

Correct Answer & Explanation

. The osteotomy moved the functional arc of motion entirely into extension

Explanation

Correcting a procurvatum deformity via an extension osteotomy shifts the entire arc of motion towards extension. If the patient had adapted their soft tissues to the flexed position, this shift typically reduces maximum terminal flexion postoperatively.

Question 50

Topic: Total Knee Arthroplasty (TKA)

A surgeon is planning a complex osteotomy for a multi-planar lower limb deformity using a hexapod circular external fixator. The patient has a combined distal femoral and proximal tibial deformity. To ensure accurate correction and prevent inducing secondary deformities, which of the following principles, as described in the case, is paramount when placing the hinge pins for the osteotomy?

. A. Hinge pins must be placed perpendicular to the mechanical axis of the limb.
. B. Hinge pins must be placed parallel to the anatomic axis of the bone.
. C. Hinge pins must be placed parallel to the joint orientation line of the adjacent joint.
. D. Hinge pins must be placed at the exact Center of Rotation of Angulation (CORA).
. E. Hinge pins must be placed to achieve a final Mechanical Lateral Distal Femoral Angle (mLDFA) and Medial Proximal Tibial Angle (MPTA) of 90 degrees.

Correct Answer & Explanation

. C. Hinge pins must be placed parallel to the joint orientation line of the adjacent joint.

Explanation

Correct Answer: CThe correct answer is C. Under the 'Surgical Pearls for Joint Orientation Mapping' section, the case explicitly states: 'When performing an opening or closing wedge osteotomy, the hinge pin must be perfectly parallel to the joint orientation line to prevent inducing an unwanted secondary deformity in the orthogonal plane.' This principle ensures that the correction occurs purely in the intended plane (e.g., frontal plane for varus/valgus) without inadvertently creating a deformity in the sagittal plane (e.g., flexion/extension).Option Ais incorrect. While the mechanical axis is crucial for overall alignment, hinge pins are oriented relative to the joint line to control the plane of correction, not necessarily perpendicular to the mechanical axis of the entire limb.Option Bis incorrect. Hinge pins are oriented relative to the joint line, not necessarily parallel to the anatomic axis of the bone, especially if the anatomic axis itself is deformed or if the osteotomy is near a joint.Option Dis incorrect. While the CORA is the apex of the deformity and the ideal location for an osteotomy, the hinge pins' orientation (parallel to the joint line) is a separate, critical principle for preventing secondary deformities, regardless of whether the osteotomy is precisely at the CORA or away from it (using Paley's rules).Option Edescribes the goal of traditional Mechanical Alignment in TKA, not a general principle for hinge pin placement in osteotomies. Furthermore, achieving 90-degree angles for mLDFA and MPTA might not be the goal for all osteotomies, especially if aiming for kinematic alignment or specific overcorrection.

Question 51

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old patient is undergoing Total Knee Arthroplasty (TKA). The surgeon is debating between a traditional Mechanical Alignment (MA) approach and a Kinematic Alignment (KA) approach. Based on the case, what is the fundamental difference in how these two philosophies utilize joint orientation lines?

. A. MA aims to restore the patient's pre-arthritic joint orientation lines, while KA aims for a neutral Mechanical Axis Deviation (MAD).
. B. MA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes, while KA aims to restore the patient's pre-arthritic joint orientation lines.
. C. MA focuses on correcting the Neck-Shaft Angle (NSA), while KA focuses on the Lateral Distal Tibial Angle (LDTA).
. D. MA prioritizes sagittal plane alignment (e.g., PDFA), while KA prioritizes frontal plane alignment (e.g., MPTA).
. E. Both MA and KA aim to achieve an MPTA of 87ยฐ and an mLDFA of 88ยฐ.

Correct Answer & Explanation

. B. MA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes, while KA aims to restore the patient's pre-arthritic joint orientation lines.

Explanation

Correct Answer: BThe correct answer is B. The case clearly differentiates Mechanical Alignment (MA) and Kinematic Alignment (KA) in TKA. It states: 'Mechanical Alignment: Traditional TKA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes. This forces the mLDFA and MPTA to be exactly 90ยฐ.' In contrast, 'Kinematic Alignment: Modern KA techniques aim to restore the patient's pre-arthritic joint orientation lines. The surgeon intentionally cuts the tibia at an MPTA of 87ยฐ and the femur at an mLDFA of 87ยฐ to match the native anatomy...'Option Aincorrectly swaps the definitions. MA aims for a neutral MAD (by making mLDFA and MPTA 90ยฐ), while KA aims to restore native joint lines.Option Cis incorrect. NSA and LDTA are not the primary distinguishing factors between MA and KA; the focus is on the knee's frontal plane angles (mLDFA, MPTA).Option Dis incorrect. Both MA and KA consider both frontal and sagittal planes, but the fundamental difference lies in their approach to frontal plane joint orientation (perpendicular to mechanical axis vs. native joint line).Option Eis incorrect. While 87ยฐ and 88ยฐ are average normal values, MA specifically aims for 90ยฐ for both mLDFA and MPTA, which often alters the native joint line. KA aims to restore theindividual patient'spre-arthritic angles, which might be around these averages but are not rigidly set to them for all patients.

Question 52

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents for Total Knee Arthroplasty (TKA). She has a mid-diaphyseal femoral malunion with 25 degrees of varus deformity. Which of the following is the most appropriate management to achieve a stable, aligned knee?

. Standard intra-articular femoral resection with a 25-degree valgus cut
. Corrective femoral osteotomy staged before TKA
. Simultaneous TKA with unconstrained polyethylene
. Standard TKA with an offset stem bypassing the deformity
. Custom TKA implant with asymmetric condyles

Correct Answer & Explanation

. Corrective femoral osteotomy staged before TKA

Explanation

Extra-articular coronal plane deformities >20 degrees in the femur generally require a corrective osteotomy rather than compensatory intra-articular resection. Intra-articular correction of such large extra-articular deformities disrupts collateral ligament balance and joint line obliquity.

Question 53

Topic: Total Knee Arthroplasty (TKA)

During preoperative planning for a TKA in a patient with an accentuated lateral femoral bow, you note an abnormally large anatomic-mechanical angle (AMA) of the femur. How does an increased femoral bow typically alter the standard distal femoral cut if referencing the intramedullary axis?

. Requires a larger valgus cut angle than standard
. Requires a smaller valgus cut angle than standard
. Requires 0 degrees of valgus
. Requires a varus cut angle
. Has no effect on the intramedullary guide

Correct Answer & Explanation

. Requires a larger valgus cut angle than standard

Explanation

The Anatomic-Mechanical Angle (AMA) of the femur normally ranges from 5-7 degrees. In an accentuated lateral femoral bow, the anatomic axis diverges more from the mechanical axis, necessitating a larger valgus cut angle (e.g., 7-9 degrees) when using an intramedullary guide.

Question 54

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old male undergoes TKA 15 years after a closing wedge high tibial osteotomy. He now has severe patella baja. Which of the following technical modifications is most appropriate to prevent patellar tendon avulsion during surgical exposure?

. Extensive lateral retinacular release
. Quadriceps snip
. V-Y quadricepsplasty
. Tibial tubercle osteotomy
. Proximal soft tissue release of the patellar tendon

Correct Answer & Explanation

. Tibial tubercle osteotomy

Explanation

Patella baja is common after closing wedge HTO, making patellar eversion difficult and dramatically increasing the risk of patellar tendon avulsion. A tibial tubercle osteotomy (TTO) safely improves exposure and allows for proximalization of the tubercle to correct the baja.

Question 55

Topic: Total Knee Arthroplasty (TKA)

In a type II valgus knee (with attenuated medial collateral ligament) undergoing TKA, what is the most appropriate component constraint if a lateral release leaves the knee unbalanced in flexion and extension?

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

Correct Answer & Explanation

. Constrained non-hinged (CCK)

Explanation

A type II valgus knee is defined by medial collateral ligament attenuation. If the knee cannot be balanced with soft tissue releases due to medial incompetence, a Constrained Condylar Knee (CCK) implant is required to provide coronal stability.

Question 56

Topic: Total Knee Arthroplasty (TKA)

A patient with osteoarthritis and a 15-degree varus deformity presents for TKA. Preoperative templating reveals an mPTA of 80 degrees and an mLDFA of 88 degrees. To achieve a neutral mechanical axis while restoring parallel joint lines, which technique is most appropriate?

. Standard distal femoral cut at 5 degrees valgus and standard tibial cut at 90 degrees to mechanical axis
. Under-resecting the medial tibia to leave it in varus
. Performing a lateral opening wedge DFO prior to TKA
. Standard tibial cut at 90 degrees and oversized asymmetric femoral component
. Standard femoral and tibial cuts combined with a massive medial epicondylar osteotomy

Correct Answer & Explanation

. Standard distal femoral cut at 5 degrees valgus and standard tibial cut at 90 degrees to mechanical axis

Explanation

The deformity is entirely in the proximal tibia (abnormal mPTA of 80; normal mLDFA of 88). Cutting the tibia perpendicular to its mechanical axis and the femur at its standard anatomic valgus angle, followed by medial release, will correct this extra-articular deformity intra-articularly without issue.

Question 57

Topic: Total Knee Arthroplasty (TKA)

During a TKA, the surgeon inadvertently cuts the proximal tibia with 15 degrees of posterior slope. What is the most likely biomechanical consequence of this error?

. Flexion instability with anterior subluxation of the femur on the tibia
. Extension gap laxity with recurvatum
. Tightness in flexion preventing more than 90 degrees of flexion
. Anterior lift-off of the tibial tray during walking
. Patellar clunk syndrome

Correct Answer & Explanation

. Flexion instability with anterior subluxation of the femur on the tibia

Explanation

Excessive posterior tibial slope functionally increases the flexion gap relative to the extension gap. This causes the femur to slide anteriorly (or tibia posteriorly) in deep flexion, leading to flexion instability.

Question 58

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female with severe rheumatoid arthritis presents for TKA. Radiographs demonstrate a 25-degree valgus deformity. On clinical examination, there is a fixed valgus contracture, and the medial collateral ligament (MCL) is completely incompetent and attenuated (Krackow Type II). Which of the following implant choices is most appropriate?

. Cruciate-retaining (CR) TKA
. Posterior-stabilized (PS) TKA with lateral release
. Medial pivot TKA
. Constrained condylar knee (CCK) or rotating hinge TKA
. Standard CR TKA with simultaneous medial collateral ligament reconstruction

Correct Answer & Explanation

. Constrained condylar knee (CCK) or rotating hinge TKA

Explanation

A Krackow Type II valgus deformity is characterized by an incompetent/attenuated MCL. Standard unconstrained implants (CR, PS) will fail due to medial instability, requiring a higher level of constraint such as a CCK or rotating hinge prosthesis.

Question 59

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male is undergoing TKA 15 years after a previous opening wedge High Tibial Osteotomy (HTO). Which of the following technical challenges is most specifically anticipated as a direct consequence of the prior opening wedge HTO?

. Patella alta requiring proximal advancement of the tibial tubercle
. Excessive external rotation of the proximal tibia
. Patella baja and difficulty everting the patella during exposure
. Medial collateral ligament attenuation requiring a hinged prosthesis
. A significant valgus extra-articular deformity

Correct Answer & Explanation

. Patella baja and difficulty everting the patella during exposure

Explanation

Opening wedge HTOs (and closing wedge to a lesser extent) typically lower the joint line and can lead to secondary patella baja. This scarring and relative shortening of the patellar tendon make patellar eversion and adequate surgical exposure during subsequent TKA very challenging.

Question 60

Topic: Total Knee Arthroplasty (TKA)

In preparing the distal femur during a TKA for a severe fixed valgus deformity (15 degrees), the surgeon decides to set femoral rotation. If the posterior condylar axis is solely relied upon for referencing, what alignment error is most likely to occur?

. Excessive external rotation of the femoral component
. Excessive internal rotation of the femoral component
. Medialization of the femoral component
. Excessive flexion of the femoral component
. Hyperextension of the femoral component

Correct Answer & Explanation

. Excessive internal rotation of the femoral component

Explanation

Severe valgus deformities are classically associated with lateral femoral condyle hypoplasia. Referencing the posterior condyles directly in this setting will internally rotate the femoral component, adversely affecting patellofemoral tracking and flexion gap balance.

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