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 141
Topic: Total Knee Arthroplasty (TKA)
A 65-year-old female complains of a painful catch and pop in her knee when extending from a flexed position, one year after a posterior-stabilized TKA. What is the most likely etiology of this classic symptom?
Correct Answer & Explanation
. Fibrous nodule formation at the superior pole of the patella engaging the intercondylar box
Explanation
Patellar clunk syndrome occurs in posterior-stabilized TKAs when a fibrous nodule forms at the superior pole of the patella and catches in the femoral intercondylar box during extension. Treatment typically involves arthroscopic debridement of the nodule.
Question 142
Topic: Total Knee Arthroplasty (TKA)
A 70-year-old male presents with inability to actively extend his knee 3 years following a primary TKA. Examination reveals a palpable gap at the patellar tendon. What is the most reliable reconstructive option for this chronic, massive disruption?
Chronic extensor mechanism disruptions post-TKA have extremely high failure rates with direct repair. Synthetic mesh (Marlex) reconstruction or a complete extensor mechanism allograft are the gold standards for restoring function.
Question 143
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old female scheduled for primary TKA reports a severe blistering skin reaction to inexpensive jewelry. Patch testing confirms a severe nickel allergy. Which of the following femoral component materials is most appropriate to prevent a hypersensitivity reaction?
Correct Answer & Explanation
. Oxidized zirconium (Oxinium) or Titanium-based implant
Explanation
Patients with severe, documented metal allergies (like nickel) should receive hypoallergenic implants. Oxidized zirconium (Oxinium) or purely titanium-based components contain minimal to no nickel and are considered safe alternatives to standard cobalt-chromium alloys.
Question 144
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old woman presents with isolated medial compartment knee osteoarthritis. Which of the following clinical or radiographic findings is a classic contraindication to performing a medial unicompartmental knee arthroplasty (UKA)?
Correct Answer & Explanation
. Patient age less than 65 years
Explanation
Classic indications/contraindications for UKA (Kozinn and Scott criteria) state that a deficient ACL is a contraindication to medial UKA because it leads to eccentric wear and early failure. While modern indications have expanded somewhat, ACL deficiency remains a strong classic contraindication for standard fixed-bearing UKA. Age and weight limits have largely been abandoned as strict contraindications.
Question 145
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old male with isolated medial compartment knee osteoarthritis is evaluated for a unicompartmental knee arthroplasty (UKA).
According to classical indications, which of the following is considered a primary contraindication to performing a medial UKA?
Correct Answer & Explanation
. Patient age greater than 60 years
Explanation
Historically, absolute contraindications for UKA included inflammatory arthropathy, ACL deficiency, fixed varus >10-15 degrees, and flexion contracture >15 degrees. ACL deficiency leads to excessive AP translation, accelerating wear and early failure of the relatively unconstrained medial UKA components. Note: Age and weight limits have been largely relaxed in modern practice.
Question 146
Topic: Total Knee Arthroplasty (TKA)
A patient presents with anterior knee pain and a sensation of instability 1 year after a primary total knee arthroplasty (TKA). Examination reveals lateral subluxation of the patella in early flexion. Radiographic and CT evaluation demonstrates malrotation of the components. Which of the following component alignment errors is most likely responsible for this finding?
Correct Answer & Explanation
. Internal rotation of the femoral component
Explanation
Internal rotation of either the femoral or the tibial component in a TKA shifts the tibial tubercle laterally relative to the trochlear groove, increasing the Q-angle. This dynamic malalignment leads to lateral patellar maltracking, anterior knee pain, and potential instability. External rotation of the components typically improves patellar tracking.
Question 147
Topic: Total Knee Arthroplasty (TKA)
A 68-year-old female presents with complaints of instability and knee effusion 6 months after a posterior-stabilized total knee arthroplasty (TKA). Examination reveals a stable knee in full extension and 90 degrees of flexion, but marked laxity at 30 to 45 degrees of flexion. What is the most likely intraoperative technical error that caused this presentation?
Correct Answer & Explanation
. Joint line elevation
Explanation
Mid-flexion instability in TKA is classically caused by joint line elevation. This occurs when excessive distal femoral resection is compensated by inserting a thicker polyethylene insert, which balances extension but leaves the mid-flexion arc loose.
Question 148
Topic: Total Knee Arthroplasty (TKA)
During primary total knee arthroplasty with trial implants in place, the surgeon notes technically satisfactory patellar resurfacing and restoration of a physiologic mechanical axis but excessively lateral patellar tracking. Treatment should now include:
Correct Answer & Explanation
. a lateral retinacular release.
Explanation
DISCUSSION: The most common causes of patellar instability after total knee arthroplasty are valgus malalignment, internal rotation of the femoral or tibial component, medialization of the femoral component, errors in patellar preparation and resurfacing, and failure to perform a lateral release. These factors should be addressed before considering capsular closure.
Question 149
Topic: Total Knee Arthroplasty (TKA)
A woman has a 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 mechanical axis deformity. When using the measured resection technique during total knee arthroplasty (TKA), the best way to avoid femoral malrotation is to reference the
Correct Answer & Explanation
. posterior condylar axis.
Explanation
Discussion: 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, as seen in varus knees. 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. This malrotation in turn leads to patellofemoral maltracking or instability, which is a common complication associated with primary TKA.
Question 150
Topic: Total Knee Arthroplasty (TKA)
In a kinematically aligned total knee arthroplasty compared to a traditional mechanically aligned TKA, the femoral component is typically placed in what position relative to the mechanical axis?
Correct Answer & Explanation
. More varus and internal rotation
Explanation
Kinematic alignment aims to restore the pre-arthritic joint lines and the natural cylindrical axis of the knee. Because the normal native distal femur has about 3 degrees of joint line valgus (which equates to varus relative to the mechanical axis perpendicular cut) and less external rotation than classic mechanical alignment cuts, the component is placed in more varus and internal rotation compared to a strictly mechanically aligned knee.
Question 151
Topic: Total Knee Arthroplasty (TKA)
A 65-year-old male is 8 weeks post-uncomplicated primary TKA and complains of significant stiffness. His range of motion is 15 to 75 degrees despite excellent compliance with aggressive physical therapy. Radiographs confirm appropriate component sizing and alignment without loosening. What is the most appropriate next step in management?
Correct Answer & Explanation
. Manipulation under anesthesia (MUA)
Explanation
Manipulation under anesthesia (MUA) is the treatment of choice for post-TKA arthrofibrosis (stiffness) that has failed to improve with aggressive physical therapy. The optimal window for MUA is generally between 6 and 12 weeks postoperatively. Waiting beyond 12 weeks decreases the success rate and increases the risk of complications such as supracondylar femur fracture or extensor mechanism disruption during the manipulation.
Question 152
Topic: Total Knee Arthroplasty (TKA)
During a complex revision TKA, the surgeon notes that the joint line has been inadvertently elevated by 8 mm compared to its pre-disease anatomic location. If left uncorrected, which of the following complications is most likely to occur postoperatively?
Correct Answer & Explanation
. Mid-flexion instability and pseudo-patella baja
Explanation
Elevation of the joint line in revision TKA is a common error resulting from excessive distal femoral resection without adequate augmentation. Because the patellar tendon length remains constant from the tibial tubercle, elevating the joint line moves the femoral trochlea proximally relative to the patella, creating a "pseudo-patella baja" (the patella sits abnormally low relative to the joint line, causing impingement and decreased ROM). Additionally, because the collateral ligaments originate on the epicondyles, moving the joint line proximally without altering the AP dimension introduces slack into the ligaments in mid-flexion, leading to mid-flexion instability. The solution is using distal femoral augments to restore the joint line distally.
Question 153
Topic: Total Knee Arthroplasty (TKA)
When performing patellar resurfacing during a primary TKA, careful attention must be paid to the remaining thickness of the native patellar bone after the resection. To minimize the risk of a catastrophic postoperative patellar fracture, what is the generally accepted absolute minimum composite thickness of the remaining native anterior patellar bone shell?
Correct Answer & Explanation
. 12 to 15 mm
Explanation
The native, unresurfaced patella is typically 22 to 26 mm thick in adults. When resurfacing the patella, the goal is to resect an amount of bone equal to the thickness of the polyethylene button being implanted to restore the native patellar composite thickness. However, if the native patella is thin or asymmetric, the surgeon must prioritize leaving an adequate residual bony shell. The established biomechanical threshold to prevent catastrophic patellar fracture is leaving an absolute minimum of 12 to 15 mm of native anterior patellar bone.
Question 154
Topic: Total Knee Arthroplasty (TKA)
A 65-year-old female complains of giving way and recurrent effusions 2 years after a primary TKA. Examination reveals symmetrical extension gap stability, but instability to varus and valgus stress at 90 degrees of flexion. Which intraoperative error most likely caused this presentation?
Correct Answer & Explanation
. Undersizing the femoral component
Explanation
Undersizing the femoral component (specifically the anteroposterior dimension) increases the flexion gap without affecting the extension gap. This mismatch leads to isolated flexion instability.
Question 155
Topic: Total Knee Arthroplasty (TKA)
A patient presents with a painful popping sensation at the superior pole of the patella when extending the knee from 45 degrees to full extension, 1 year after a posterior-stabilized TKA. What is the most appropriate management?
Correct Answer & Explanation
. Arthroscopic excision of the fibrotic nodule
Explanation
This is the classic presentation of patellar clunk syndrome, caused by a fibrotic nodule forming at the superior pole of the patella that catches in the intercondylar box of a posterior-stabilized femur. Arthroscopic excision of the nodule provides excellent results.
Question 156
Topic: Total Knee Arthroplasty (TKA)
In total knee arthroplasty, the concept of kinematic alignment has gained popularity. Compared to traditional mechanical alignment, kinematic alignment aims to position the femoral component by matching which of the following patient-specific axes?
Correct Answer & Explanation
. The pre-arthritic cylindrical axis of the femoral condyles
Explanation
Kinematic alignment in TKA aims to restore the patient's pre-arthritic constitutional alignment by co-aligning the transverse axis of the femoral component with the primary transverse axis of the knee, which is the cylindrical axis of the femoral condyles. It achieves this by resurfacing the condyles with equal thicknesses of metal matching the resected bone and cartilage.
Question 157
Topic: Total Knee Arthroplasty (TKA)
Kinematic alignment in total knee arthroplasty aims to restore the patient's pre-arthritic constitutional alignment. Compared to traditional mechanical alignment, a strictly kinematically aligned TKA most typically results in the components being positioned in which manner relative to the mechanical axis?
Correct Answer & Explanation
. The tibial component in slight varus and the femoral component in slight valgus
Explanation
Kinematic alignment co-aligns the component axes with the native kinematic axes of the knee, restoring the pre-arthritic joint line obliquity. Because the native proximal tibia typically has about 3 degrees of varus and the distal femur has corresponding valgus, the resulting components are placed in slight tibial varus and femoral valgus relative to the strict mechanical axes.
Question 158
Topic: Total Knee Arthroplasty (TKA)
In calipered kinematic alignment total knee arthroplasty, what is the primary surgical goal regarding the placement of the femoral component?
Correct Answer & Explanation
. Restoring the pre-arthritic articular surface by matching the native posterior and distal femoral joint lines
Explanation
The central tenet of kinematic alignment in TKA is restoring the native, pre-arthritic joint lines and kinematic axes of the knee. This is achieved by removing only the precise thickness of bone and cartilage that corresponds to the thickness of the implant.
Question 159
Topic: Total Knee Arthroplasty (TKA)
A patient presents with a painful popping sensation at the superior aspect of the patella when extending the knee from a flexed position, 8 months after a primary total knee arthroplasty. This complication is most classically associated with which implant design?
Correct Answer & Explanation
. Posterior-stabilized (PS) TKA
Explanation
Patellar clunk syndrome is classically associated with posterior-stabilized (PS) TKA designs. It occurs when a fibrous nodule forms at the superior pole of the patella and catches in the femoral intercondylar box during extension.
Question 160
Topic: Total Knee Arthroplasty (TKA)
A patient with severe lateral bowing of the femur in the coronal plane is undergoing a TKA. If a standard straight intramedullary alignment rod is used without adjustments, what will be the likely effect on the distal femoral resection?
Correct Answer & Explanation
. An excessive varus distal femoral cut
Explanation
When using an intramedullary guide in a femur with significant lateral coronal bowing, the rod is forced medially at the distal aspect. This leads to a relatively varus distal femoral resection if not preoperatively templated and adjusted.
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