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 61
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old male with end-stage knee osteoarthritis presents with an extra-articular diaphyseal varus deformity of the femur following a prior fracture. The deformity is located 10 cm proximal to the joint line. At what degree of coronal plane angulation is a simultaneous or staged extra-articular corrective osteotomy typically recommended prior to or during TKA?
Correct Answer & Explanation
. Greater than 20 degrees
Explanation
Intra-articular compensatory bone cuts during TKA can typically manage extra-articular femoral coronal deformities up to 20 degrees. Deformities >20 degrees in the femur (or >15 in the tibia) usually necessitate a staged or concurrent extra-articular osteotomy to avoid collateral ligament compromise.
Question 62
Topic: Total Knee Arthroplasty (TKA)
During TKA utilizing standard extramedullary tibial alignment guides, a patient is noted to have excessive anterior bowing of the tibial shaft. If the surgeon aligns the extramedullary guide parallel to the anterior tibial crest without fluoroscopic verification, what error is most likely to occur in the tibial bone cut?
Correct Answer & Explanation
. Excessive posterior tibial slope
Explanation
The anterior crest of a bowed tibia curves anteriorly away from the mechanical axis. If the guide is placed parallel to this bowed crest, the cutting block pitches posteriorly, resulting in a cut with excessive posterior slope.
Question 63
Topic: Total Knee Arthroplasty (TKA)
A surgeon is evaluating a 55-year-old patient for a TKA. The patient has a severe extra-articular varus deformity of the proximal tibia. According to Wolff and Paley's recommendations for TKA in the setting of extra-articular deformity, an intra-articular compensatory cut becomes absolutely contraindicated (mandating an osteotomy) when the theoretical cut does what?
Correct Answer & Explanation
. Compromises the collateral ligament insertions.
Explanation
Intra-articular compensatory cuts for extra-articular deformities are limited by the anatomy of the knee. If the required bone cut is so severe that it would excise or irreparably compromise the origins or insertions of the collateral ligaments, an extra-articular osteotomy must be performed instead.
Question 64
Topic: Total Knee Arthroplasty (TKA)
During conventional TKA using an intramedullary femoral alignment guide, a patient is noted to have significant excessive anterior bowing of the femoral diaphysis. If the distal femoral cut is made using the standard intramedullary rod without compensation, what sagittal plane error is most likely to occur?
Correct Answer & Explanation
. Excessive extension of the femoral component.
Explanation
Excessive anterior femoral bowing causes the rigid IM rod to be directed more anteriorly in the distal femur. If the cut is based on this uncompensated trajectory, it leads to relative extension of the femoral component, potentially tightening the flexion gap.
Question 65
Topic: Total Knee Arthroplasty (TKA)
A 68-year-old female with primary osteoarthritis and a severely lateral bowed femur is undergoing TKA. How should the surgeon alter the entry point for the intramedullary alignment rod to ensure a perpendicular distal femoral cut relative to the mechanical axis?
Correct Answer & Explanation
. Move the entry point medial to the anatomic intercondylar notch.
Explanation
In a femur with excessive lateral bowing, the IM canal directs the rod in varus relative to the mechanical axis. To compensate and avoid a varus resection, the IM rod entry point should be moved medial to the true center of the anatomic notch.
Question 66
Topic: Total Knee Arthroplasty (TKA)
A 70-year-old female presents with end-stage medial compartment osteoarthritis of the left knee and a history of a malunited mid-diaphyseal femoral fracture from 20 years ago. Full-length standing radiographs confirm a significant extra-articular femoral varus deformity. She is a candidate for total knee arthroplasty (TKA). Based on Paley's principles and the biomechanical consequences of malalignment, what is the most appropriate surgical strategy?
Correct Answer & Explanation
. Perform a corrective osteotomy of the femur to restore the mechanical axis, followed by a staged TKA.
Explanation
Correct Answer: BThe case describes a patient with end-stage medial compartment OA and a significant extra-articular femoral varus deformity. The text explicitly states that 'In severe cases—particularly if the bone deformity is extra-articular (e.g., a femoral diaphyseal malunion)—it is often necessary to treat the bone malunion with a corrective osteotomybeforeattempting a TKR.' Proper realignment of severe deformities in preparation for TKR simplifies the eventual arthroplasty, restores the mechanical axis, and ensures the longevity of the implants. Attempting to correct a severe extra-articular deformity solely with intra-articular bone cuts and soft tissue releases during TKA can lead to suboptimal alignment, implant loosening, and premature wear.Option A is incorrectbecause while some intra-articular correction is possible, severe extra-articular deformities are best addressed with a separate osteotomy to restore the overall limb alignment before TKA.Option C is incorrectbecause while constrained implants might be considered for severe instability, addressing the underlying bony deformity first is paramount to achieve a stable, well-aligned knee, which may then allow for a less constrained implant or improve the longevity of any implant.Option D is incorrectbecause the primary deformity is in the femur, not the tibia. A high tibial osteotomy would be inappropriate and would create a 'zig-zag' mechanical axis, compounding the problem.Option E is incorrectbecause TKA is not contraindicated. While challenging, a staged approach with osteotomy followed by TKA is a recognized and effective strategy for such complex cases.
Question 67
Topic: Total Knee Arthroplasty (TKA)
A 62-year-old male presents with chronic right knee pain, worse with activity. Standing long AP radiographs reveal unicompartmental medial tibiofemoral arthrosis. The mechanical axis passes 20 mm medial to the center of the knee. The patient is otherwise healthy and desires joint preservation. Based on the principles outlined in the case, what is the most accurate and actionable term to describe the primary pathology driving this patient's condition?
Correct Answer & Explanation
. C. Mechanical arthrosis
Explanation
Correct Answer: CThe case explicitly distinguishes between 'degenerative arthritis' and 'mechanical arthrosis.' It states, 'The primary pathology we confront in the setting of a crooked limb is not systemic or inflammatory in origin; it is purely mechanical.' The term 'mechanical arthrosis' is highlighted as 'more precise, actionable, and etiologically correct' because it directly points to the mechanical engineering problem of malalignment and pathological stress distribution as the root cause of cartilage failure, rather than a vague 'degenerative' process or inflammation (which is a downstream consequence). The patient's presentation with unicompartmental medial tibiofemoral arthrosis and a significant medial mechanical axis deviation (20 mm medial) perfectly aligns with the definition of mechanical arthrosis due to chronic overload.Incorrect Options:A. Primary osteoarthritis:While clinically often used, the case argues this is a misnomer in the context of limb malalignment, as it doesn't address the underlying mechanical etiology.B. Inflammatory arthropathy:The case explicitly states that the pathology in malalignment is 'not systemic or inflammatory in origin.' Inflammation is a secondary biological response, not the primary cause.D. Degenerative joint disease:Similar to 'primary osteoarthritis,' the case identifies 'degenerative arthritis' as a 'profound misnomer that distracts from the true etiology' when malalignment is present.E. Senescent cartilage failure:While age-related cartilage changes contribute, this term doesn't capture the specific, correctable mechanical etiology of the patient's unicompartmental disease driven by malalignment.
Question 68
Topic: Total Knee Arthroplasty (TKA)
A 38-year-old male undergoes a medial opening wedge high tibial osteotomy (HTO) for varus gonarthrosis. The osteotomy is intentionally performed proximal to the tibial tubercle. Which of the following is an expected biomechanical consequence on the patellofemoral joint postoperatively?
Correct Answer & Explanation
. Patella baja (infera)
Explanation
Performing a medial opening wedge HTO proximal to the tibial tubercle lengthens the proximal tibia without altering the tibial tubercle's distal position. This effectively lowers the relative position of the patella to the joint line, creating an iatrogenic patella baja (infera).
Question 69
Topic: Total Knee Arthroplasty (TKA)
A 62-year-old male is planned for a primary total knee arthroplasty (TKA). He has an old malunited femoral shaft fracture causing an extra-articular varus deformity. According to established principles, an extra-articular deformity typically requires a simultaneous or staged corrective osteotomy prior to TKA if the coronal plane angulation exceeds what threshold?
Correct Answer & Explanation
. 10 to 15 degrees in the femur.
Explanation
Extra-articular femoral deformities >10-15 degrees (or tibial >20 degrees) generally cannot be corrected solely by intra-articular bone cuts during TKA without compromising collateral ligament origins/insertions, thus requiring an osteotomy.
Question 70
Topic: Total Knee Arthroplasty (TKA)
When performing a distal femoral extension osteotomy (DFEO) for a severe soft tissue flexion contracture of the knee (e.g., in a patient with cerebral palsy), what intentional osseous deformity is created to compensate for the contracted soft tissues?
Correct Answer & Explanation
. Femoral recurvatum
Explanation
A DFEO creates an intentional osseous recurvatum (apex posterior) deformity in the distal femur. This compensates for the soft tissue flexion contracture, allowing the leg to achieve a straight mechanical alignment for weight-bearing.
Question 71
Topic: Total Knee Arthroplasty (TKA)
A 45-year-old male is undergoing a high tibial osteotomy for a severe medial compartment osteoarthritis and varus deformity. Paley's analysis reveals a tibial deformity with the CORA located at the joint line. If a proximal tibial osteotomy is performed distal to the CORA (Paley's Rule 2) and corrected by angulation alone, what is the resulting mechanical alignment?
Correct Answer & Explanation
. The mechanical axes will be parallel but translated, creating a zigzag deformity.
Explanation
Paley's Osteotomy Rule 2 indicates that if an osteotomy is performed at a level different from the CORA and corrected by angulation alone, the proximal and distal mechanical axes will be parallel but translated. To make them collinear, translation at the osteotomy site must accompany the angulation (Rule 3).
Question 72
Topic: Total Knee Arthroplasty (TKA)
A 35-year-old male with chronic LCL laxity and a varus thrust undergoes a proximal tibial osteotomy. The surgeon aims to dynamically tension the deficient lateral structures by altering the mechanical axis. Which target mechanical alignment is most appropriate to eliminate the varus thrust in this patient?
Correct Answer & Explanation
. 3 to 5 degrees of mechanical valgus (MAD lateral to the center of the knee).
Explanation
In the presence of lateral collateral ligament (LCL) laxity and a varus thrust, overcorrecting the mechanical axis into 3 to 5 degrees of mechanical valgus forces the knee into a valgus position during stance. This tensions the lateral soft-tissue sleeve and dynamically eliminates the varus thrust.
Question 73
Topic: Total Knee Arthroplasty (TKA)
A 55-year-old male with medial unicompartmental osteoarthritis and a varus deformity is being evaluated for a High Tibial Osteotomy (HTO). Which of the following is considered an absolute contraindication to performing an isolated valgus-producing HTO?
Correct Answer & Explanation
. Advanced full-thickness chondral loss in the lateral compartment.
Explanation
A valgus-producing HTO shifts the weight-bearing axis into the lateral compartment. Advanced lateral compartment osteoarthritis (full-thickness chondral loss) is an absolute contraindication, as the increased lateral loading will cause rapid symptom progression.
Question 74
Topic: Total Knee Arthroplasty (TKA)
According to Paley's principles, if an osteotomy is performed exactly at the Center of Rotation of Angulation (CORA) but the hinge (ACA) is placed eccentric to the CORA (Osteotomy Rule 1 variant), what will be the resulting mechanical alignment?
Correct Answer & Explanation
. Collinear axes but with length gain or loss.
Explanation
If the osteotomy is at the CORA but the ACA is eccentric to it (like placing a hinge on the cortex rather than the central axis), the mechanical axes remain collinear, but there is an intentional or consequential opening/closing wedge effect that alters the absolute length of the bone segment.
Question 75
Topic: Total Knee Arthroplasty (TKA)
According to Paley's Rule 1 of deformity correction, if the osteotomy and the hinge (axis of rotation) are both placed exactly at the Center of Rotation of Angulation (CORA), what is the resultant anatomic and mechanical alignment?
Correct Answer & Explanation
. Both the mechanical and anatomic axes are restored without any translation.
Explanation
Paley's Rule 1 states that when the osteotomy and the hinge are both placed at the CORA, the bone undergoes pure angulation. This fully restores both the anatomic and mechanical axes without introducing any translation.
Question 76
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old patient presents with severe knee osteoarthritis and a significant varus deformity. Preoperative planning for a corrective osteotomy involves assessing the overall global limb alignment. According to the text, which specific line is considered the most important for this assessment?
Correct Answer & Explanation
. C. The mechanical axis of the entire limb (Mikulicz Line).
Explanation
Correct Answer: CThe text defines the 'Entire Limb (Mikulicz Line)' as 'A single line from the center of the femoral head to the center of the ankle. This is the most important line for assessing overall global limb alignment.' Restoring this line to pass through the center of the knee is the biomechanical imperative of deformity correction.Incorrect Options:A. The anatomic axis of the femur:While important for intramedullary nailing, the femoral anatomic axis does not represent the global mechanical alignment of the entire limb due to its divergence from the mechanical axis.B. The anatomic axis of the tibia:Similar to the femoral anatomic axis, the tibial anatomic axis represents the mid-diaphyseal line of the tibia, not the global mechanical alignment of the entire limb.D. The line connecting the center of the femoral head to the greater trochanter:This line is not a standard axis for assessing lower extremity alignment in the frontal plane.E. The line connecting the midpoint of the tibial spines to the center of the ankle plafond:This describes the mechanical axis of thetibiaonly, not the overall global limb alignment from hip to ankle.
Question 77
Topic: Total Knee Arthroplasty (TKA)
When planning a deformity correction, multiple CORAs may be identified in a single bone segment. Which of the following best describes the primary biomechanical indication for utilizing a double-level osteotomy rather than a single-level correction?
Correct Answer & Explanation
. When a single osteotomy would result in unacceptable translation of the anatomical axis to restore mechanical alignment.
Explanation
Multiple CORAs or a large diaphyseal bow corrected with a single osteotomy near the joint may result in significant, unacceptable bone translation. A double-level osteotomy restores the mechanical axis while maintaining the anatomical axis within the soft tissue envelope.
Question 78
Topic: Total Knee Arthroplasty (TKA)
A 62-year-old patient with unicompartmental knee osteoarthritis and a significant angular deformity is being considered for either a realignment osteotomy or total knee arthroplasty (TKA). Which of the following patient characteristics would most strongly favor an osteotomy over a TKA?
Correct Answer & Explanation
. High activity level with good bone stock and no inflammatory arthritis.
Explanation
Correct Answer: DRealignment osteotomy is generally preferred for younger, active patients with unicompartmental osteoarthritis, good bone stock, and no inflammatory arthritis. These patients often desire to maintain a high activity level, including sports, which may be limited or contraindicated after TKA. Osteotomy preserves the native joint and allows for future TKA if needed. The image illustrates the concept of correcting deformity to restore alignment, which is the goal of osteotomy in such patients.Option A, a sedentary lifestyle with multiple comorbidities, would typically favor TKA, especially if the patient's activity demands are low and the risks of osteotomy (longer recovery, potential for nonunion) outweigh the benefits. Option B, advanced tricompartmental osteoarthritis, is a strong contraindication for osteotomy, as osteotomy is designed for unicompartmental disease. TKA would be the treatment of choice. Option C, age greater than 70 years, generally favors TKA due to the higher likelihood of advanced osteoarthritis, lower activity demands, and faster recovery compared to osteotomy. Option E, significant knee instability and ligamentous laxity, is often a contraindication for osteotomy, as osteotomy primarily corrects angular deformity and does not address ligamentous instability. TKA, especially with constrained components, might be more appropriate in such cases.
Question 79
Topic: Total Knee Arthroplasty (TKA)
A 60-year-old female presents with severe knee osteoarthritis and a suspected varus deformity. The orthopedic surgeon emphasizes the need for a full-length standing anteroposterior (AP) radiograph of the lower limbs for preoperative planning. Why is this specific type of radiograph considered the 'only acceptable starting point' for deformity analysis, according to Paley's principles?
Correct Answer & Explanation
. It allows for accurate assessment of the global mechanical relationship between all joints of the lower extremity under weight-bearing conditions.
Explanation
Correct Answer: BThe text explicitly states: 'The full-length film is essential to visualize the continuous line of weight-bearing force from the center of the femoral head down to the ankle joint.' It further clarifies that standard, short-cassette radiographs 'provide a myopic, localized view that completely obscures the global mechanical relationship between the joints of the lower extremity.' Therefore, the full-length standing AP radiograph is crucial for assessing the global mechanical alignment under functional weight-bearing conditions.Option A is incorrectbecause the text states that standard, short-cassette radiographs 'are useful for diagnosing intra-articular pathology (like joint space narrowing or osteophytes),' implying that full-length films are not primarily superior for this specific purpose, but rather for global alignment.Option C is incorrectbecause femoral anteversion and tibial torsion are rotational deformities best assessed by specialized CT scans or clinical examination, not primarily by a frontal plane AP radiograph.Option D is incorrectbecause a full-length radiograph typically involves a larger field of view and potentially more radiation than a single short-cassette view, though it avoids multiple exposures if several short views were needed to cover the entire limb. The primary reason for its use is diagnostic accuracy, not radiation minimization.Option E is incorrectbecause while severe soft tissue contractures might be inferred, the primary purpose of the full-length AP radiograph is bony alignment and mechanical axis assessment, not direct soft tissue evaluation.
Question 80
Topic: Total Knee Arthroplasty (TKA)
A 55-year-old male presents with chronic medial knee pain. A full-length standing radiograph reveals that the mechanical axis of the lower limb passes 18 mm medial to the center of the knee joint. Based on Paley's principles, what is the most accurate interpretation of this finding and its biomechanical implication?
Correct Answer & Explanation
. The patient has a varus deformity, resulting in increased loading of the medial compartment of the knee.
Explanation
Correct Answer: CThe text defines the mechanical axis of the lower limb as a line from the center of the femoral head to the center of the ankle mortise. It states, 'In a perfectly aligned limb, this line passes directly through the center of the knee joint (or slightly medial, typically 8±7 mm medial to the center).' It further clarifies, 'When the mechanical axis falls medial to the knee center, the patient has a varus deformity (bow-legged).' The biomechanical implication is that 'A medial MAD overloads the medial compartment of the knee, leading to medial unicompartmental osteoarthritis.' An 18 mm medial deviation is significantly outside the normal range (8±7 mm medial) and indicates a varus deformity with medial compartment overload.Option A is incorrectbecause a valgus deformity occurs when the mechanical axis falls lateral to the knee center, not medial.Option B is incorrectbecause procurvatum is a sagittal plane deformity (anterior bow), whereas MAD in the coronal plane assesses varus/valgus.Option D is incorrectbecause recurvatum is a sagittal plane deformity (posterior bow), not a coronal plane deviation.Option E is incorrectbecause an 18 mm medial deviation is outside the normal range of 8±7 mm medial, indicating a significant varus malalignment that is highly likely related to the knee pain.
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