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Lower Extremity Trauma MCQs

Practice Set 12 of 34

This practice set contains high-yield board review questions covering key concepts in Lower Extremity Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 221

Topic: Lower Extremity Trauma

A 70-year-old female with end-stage medial compartment osteoarthritis and a severe varus knee deformity is being evaluated for a high tibial osteotomy. Radiographs show significant medial joint space narrowing and lateral joint gapping. Her Joint Line Congruency Angle (JLCA) is measured at 7 degrees. Based on the Paley principles, what does this specific JLCA measurement primarily indicate?

. A. The deformity is exclusively located in the distal femur, requiring a distal femoral osteotomy.
. B. The knee joint lines are perfectly parallel, indicating balanced soft tissues.
. C. There is significant joint incongruity, likely due to asymmetric cartilage loss and/or lateral ligamentous laxity.
. D. The mechanical axis passes precisely through the center of the knee joint.
. E. The patient has a physiological varus alignment, and no surgical intervention is warranted.

Correct Answer & Explanation

. C. There is significant joint incongruity, likely due to asymmetric cartilage loss and/or lateral ligamentous laxity.

Explanation

Correct Answer: CThe case content defines the Joint Line Congruency Angle (JLCA) as the angle between tangential lines to the distal femur and proximal tibia articular surfaces. A normal JLCA is 0° to 2°, indicating nearly parallel joint lines and competent ligaments. An increased angle (>2°), such as the 7 degrees in this patient, is a 'massive red flag' for severe joint incongruity, asymmetric cartilage loss (medial collapse), and/or significant lateral ligamentous laxity. This finding is highly predictive of a dynamic varus thrust during gait and indicates a complex reconstructive challenge.Option A is incorrectbecause the JLCA primarily assesses joint line parallelism and soft tissue competence, not the specific location of the bony deformity (which would be determined by angles like mLDFA or MPTA). While a DFO might be needed, the JLCA itself doesn't pinpoint the bony segment.Option B is incorrectbecause a JLCA of 7 degrees is significantly abnormal and indicates severe joint incongruity, meaning the joint lines are far from parallel.Option D is incorrectbecause the JLCA measures joint line parallelism, not the position of the mechanical axis relative to the knee center (which is the Mechanical Axis Deviation, MAD).Option E is incorrectbecause a JLCA of 7 degrees is pathologically high, indicating severe deformity and instability, far from physiological alignment, and strongly warrants surgical consideration.

Question 222

Topic: Lower Extremity Trauma

A 30-year-old male presents with a progressive varus deformity of his right lower extremity. A full-length standing radiograph is obtained for deformity analysis. The surgeon measures the angle formed between the mechanical axis of the tibia and the tangent to the proximal tibial articular surface, as shown in the diagram. This angle is found to be 80 degrees. Based on the Paley principles and the provided image, what does this measurement most accurately indicate?

. A. The deformity is located in the distal femur, requiring a distal femoral osteotomy.
. B. The patient has a normal physiological alignment of the proximal tibia.
. C. The patient has tibia vara, with the deformity located in the proximal tibia.
. D. The knee joint has significant lateral ligamentous laxity.
. E. The mechanical axis of the entire limb is in valgus alignment.

Correct Answer & Explanation

. C. The patient has tibia vara, with the deformity located in the proximal tibia.

Explanation

Correct Answer: CThe diagram (ch_278_fig_847647.webp) illustrates the Medial Proximal Tibial Angle (MPTA). The case content defines the MPTA as determining proximal tibial coronal alignment, with a normal range of 85° to 90° (average 87°). A low MPTA (<85°), such as the 80 degrees measured in this patient, definitively indicates tibia vara. This specific angular change proves that the deformity is located within the proximal tibia itself, guiding the surgeon towards a High Tibial Osteotomy (HTO) for correction.Option A is incorrectbecause an abnormal MPTA specifically points to a deformity in the proximal tibia, not the distal femur. Distal femoral deformities are assessed by the mLDFA.Option B is incorrectbecause a normal MPTA is 85-90 degrees. An MPTA of 80 degrees is pathologically low, indicating a varus deformity of the proximal tibia.Option D is incorrectbecause while lateral ligamentous laxity can be associated with varus knees, the MPTA directly measures bony alignment of the proximal tibia, not soft tissue laxity. JLCA is used for joint line congruity and ligamentous laxity.Option E is incorrectbecause tibia vara (low MPTA) contributes to overall limb varus, not valgus alignment. The mechanical axis would be shifted medially.

Question 223

Topic: Lower Extremity Trauma

A 40-year-old patient undergoes a full-length standing radiograph as part of a routine orthopedic evaluation. The mechanical axis of the lower limb is measured and found to pass approximately 8 mm medial to the center of the tibial plateau. Based on the Paley principles of deformity analysis, what does this measurement indicate?

. A. The patient has a pathological varus deformity requiring immediate intervention.
. B. The patient has a pathological valgus deformity, as the axis should be lateral to the knee center.
. C. This represents a normal, physiological mechanical axis deviation (MAD).
. D. The patient has severe lateral compartment overloading.
. E. The measurement is indicative of a fixed flexion deformity of the knee.

Correct Answer & Explanation

. C. This represents a normal, physiological mechanical axis deviation (MAD).

Explanation

Correct Answer: CThe case content explicitly defines the normal Mechanical Axis Deviation (MAD) for a healthy lower limb: 'In a normal, healthy lower limb, the mechanical axis does not pass perfectly through the dead center of the knee. Instead, it passes slightly medial to the center of the knee joint, creating a physiologic Mechanical Axis Deviation (MAD) of approximately 8 mm medial to the center of the tibial plateau.' This slight medial deviation results in the normal, inherent adduction moment and physiological load distribution across the knee.Option A is incorrectbecause 8 mm medial deviation is the normal physiological MAD, not a pathological varus deformity.Option B is incorrectbecause the normal axis is slightly medial, not lateral. A lateral deviation would indicate a valgus deformity.Option D is incorrectbecause this normal MAD results in the physiological load distribution (68% medial, 32% lateral), not severe lateral compartment overloading. Lateral overloading occurs in valgus deformities.Option E is incorrectbecause MAD measures coronal plane alignment, not sagittal plane deformities like fixed flexion.

Question 224

Topic: Lower Extremity Trauma

A 60-year-old patient presents with the clinical appearance shown in the image, consistent with genu varum. Full-length weight-bearing radiographs are obtained for deformity analysis. The measurements reveal a mechanical Lateral Distal Femoral Angle (mLDFA) of 88° and a Medial Proximal Tibial Angle (MPTA) of 80°. Based on Paley's principles, where is the primary frontal plane deformity located?

. Distal femur
. Proximal tibia
. Ankle joint
. Midfoot
. Knee joint (intra-articular)

Correct Answer & Explanation

. Proximal tibia

Explanation

Correct Answer: BAccording to the provided table, the normal range for mLDFA is 85-90°, and for MPTA is 85-90°. An mLDFA of 88° falls within the normal range, indicating no significant frontal plane deformity in the distal femur. However, an MPTA of 80° is less than 85°, which indicates tibial varus. Therefore, the primary frontal plane deformity is located in the proximal tibia. The clinical appearance of genu varum is consistent with a proximal tibial varus. Option E (Knee joint intra-articular) would be suggested by an abnormal JLCA, which is not provided here.

Question 225

Topic: Lower Extremity Trauma

A 45-year-old female presents with medial knee pain. Radiographs reveal a mechanical Medial Proximal Tibial Angle (mMPTA) of 80 degrees and a mechanical Lateral Distal Femoral Angle (mLDFA) of 88 degrees. What is the primary source of her varus deformity?

. The distal femur
. The proximal tibia
. The knee joint line soft tissues
. Extra-articular femoral shaft bowing
. Both the femur and tibia contribute equally

Correct Answer & Explanation

. The proximal tibia

Explanation

The normal mMPTA is 87 degrees (range 85-90). An mMPTA of 80 degrees indicates a significant varus deformity originating intrinsically in the proximal tibia. The mLDFA of 88 degrees is within normal limits, ruling out a femoral contribution.

Question 226

Topic: Lower Extremity Trauma

A patient undergoes correction of a severe procurvatum deformity of the distal femur. The normal mechanical Posterior Distal Femoral Angle (mPDFA) referenced during planning is approximately:

. 83 degrees
. 90 degrees
. 79 degrees
. 88 degrees
. 95 degrees

Correct Answer & Explanation

. 83 degrees

Explanation

The normal mechanical Posterior Distal Femoral Angle (mPDFA) in the sagittal plane is approximately 83 degrees. Deviations from this angle indicate a procurvatum or recurvatum deformity at the distal femur.

Question 227

Topic: Lower Extremity Trauma

A patient presents with a severe valgus deformity of the knee. Radiographic analysis reveals a mechanical lateral distal femoral angle (mLDFA) of 78 degrees and a normal mechanical medial proximal tibial angle (mMPTA) of 87 degrees. Where is the primary center of deformity?

. Proximal tibia
. Distal femur
. Intra-articular knee joint
. Proximal femur
. Diaphysis of the tibia

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is approximately 87-88 degrees. An mLDFA of 78 degrees indicates a significant valgus deformity originating in the distal femur. The normal mMPTA confirms the tibia is not the primary source of the valgus.

Question 228

Topic: Lower Extremity Trauma

A patient with a tibial shaft deformity has an osteotomy performed strictly following Paley's Rule 3. The hinge is placed at the osteotomy site, which is located 4 cm away from the CORA. What is the expected biomechanical consequence?

. Perfect alignment of the mechanical axis without translation.
. Pure translation of the bone ends.
. Creation of a secondary translation deformity.
. Complete failure of regenerate bone formation.
. Immediate correction of the joint line convergence angle.

Correct Answer & Explanation

. Creation of a secondary translation deformity.

Explanation

Paley's Rule 3 states that if the osteotomy and the hinge are both separated from the CORA, angular correction will result in a secondary translation deformity. This leads to a zig-zag deformity and fails to collinearly align the proximal and distal mechanical axes.

Question 229

Topic: Lower Extremity Trauma

When evaluating a patient's standing AP radiograph for mechanical axis deviation (MAD), the Joint Line Convergence Angle (JLCA) is measured at 6 degrees converging medially (normal is 0-2 degrees). What does this finding indicate?

. Normal physiological alignment.
. A purely extra-articular diaphyseal deformity.
. Intra-articular deformity or ligamentous laxity causing joint space opening.
. A severe fixed valgus deformity of the distal femur.
. An excessive mechanical medial proximal tibial angle.

Correct Answer & Explanation

. Intra-articular deformity or ligamentous laxity causing joint space opening.

Explanation

The JLCA evaluates the parallelism of the knee joint lines. An abnormally high JLCA (e.g., 6 degrees) implies that the mechanical axis deviation is partly or completely due to intra-articular causes, such as lateral cartilage loss or lateral collateral ligament laxity.

Question 230

Topic: Lower Extremity Trauma

A 25-year-old female presents with bilateral knee pain and clinical genu valgum. Full-length standing radiographs reveal a mechanical axis deviation (MAD) of 25 mm laterally on the right leg. The surgeon measures joint orientation angles to isolate the source of the deformity. Which of the following values strongly indicates that the femur is the primary source of her valgus deformity?

. Mechanical lateral distal femoral angle (mLDFA) of 81 degrees.
. Mechanical medial proximal tibial angle (mMPTA) of 88 degrees.
. Mechanical lateral distal femoral angle (mLDFA) of 95 degrees.
. Mechanical medial proximal tibial angle (mMPTA) of 95 degrees.
. Anatomic lateral distal femoral angle (aLDFA) of 81 degrees.

Correct Answer & Explanation

. Mechanical lateral distal femoral angle (mLDFA) of 81 degrees.

Explanation

The normal mLDFA is approximately 87-88 degrees. An mLDFA significantly less than 85 degrees (such as 81 degrees) indicates a valgus deformity of the distal femur. An mLDFA of 95 degrees would indicate femoral varus.

Question 231

Topic: Lower Extremity Trauma



A 45-year-old man undergoes deformity analysis. His standing lower extremity radiograph demonstrates a mechanical axis line that passes 15 mm medial to the center of the knee joint. What does this specific mechanical axis deviation (MAD) imply regarding the joint reactive forces at the knee?

. A balanced distribution of load across both medial and lateral compartments.
. An exponential increase in lateral compartment joint reactive forces.
. A substantially increased load across the medial compartment, predisposing to early osteoarthritis.
. A primary deformity driven solely by a depressed lateral tibial plateau.
. Reversal of the normal tensile forces in the lateral collateral ligament.

Correct Answer & Explanation

. A substantially increased load across the medial compartment, predisposing to early osteoarthritis.

Explanation

A medial mechanical axis deviation (MAD) indicates varus malalignment. This places disproportionately high joint reactive forces on the medial compartment of the knee, accelerating medial articular wear and cartilage breakdown.

Question 232

Topic: Lower Extremity Trauma

When assessing the mechanical axis of the tibia for deformity correction, which anatomical landmarks are used to define the proximal and distal points?

. Center of the tibial plateau to the center of the tibial plafond
. Medial tibial spine to the medial malleolus
. Center of the tibial tubercle to the lateral malleolus
. Lateral tibial spine to the center of the talus
. Center of the intercondylar eminence to the tip of the medial malleolus

Correct Answer & Explanation

. Center of the tibial plateau to the center of the tibial plafond

Explanation

The mechanical axis of the tibia is defined by a line drawn from the center of the proximal tibial plateau to the center of the distal tibial plafond.

Question 233

Topic: Lower Extremity Trauma



A patient presents with a multi-apical deformity of the tibia. During preoperative templating, the surgeon defines the mechanical axes and identifies two distinct CORAs. What is the standard recommended strategy to perfectly correct this deformity without creating secondary translation?

. A single osteotomy at the proximal CORA with a hinge at the distal CORA.
. A single osteotomy exactly halfway between the two CORAs.
. Two separate osteotomies, each with a hinge placed at its respective CORA.
. A single opening wedge osteotomy at the apex of the larger deformity only.
. A transverse osteotomy through the diaphysis with immediate intramedullary nailing.

Correct Answer & Explanation

. Two separate osteotomies, each with a hinge placed at its respective CORA.

Explanation

For multi-apical deformities, the most precise way to achieve colinear mechanical axes without unwanted translation is to follow Paley's Rule 1 for each apex. This requires an osteotomy and hinge at each distinct CORA.

Question 234

Topic: Lower Extremity Trauma

A 55-year-old female presents with a symptomatic varus knee deformity. Long-leg radiographs show a Mechanical Lateral Distal Femoral Angle (mLDFA) of 88° and a Medial Proximal Tibial Angle (MPTA) of 80°. Based on these measurements, where is the primary anatomical source of her deformity?

. Distal femur
. Proximal tibia
. Proximal femur
. Distal tibia
. Joint line convergence

Correct Answer & Explanation

. Proximal tibia

Explanation

Correct Answer: BThe text provides the normal value ranges for joint orientation angles. The normal mLDFA is 85° to 90° (Avg 87°). A value of 88° falls within this normal range, indicating that there is no significant valgus or varus deformity originating in the distal femur. The normal MPTA is 85° to 90° (Avg 87°). A value of 80° is less than 85°, which, according to the table, indicates a varus deformity originating in the proximal tibia. Therefore, the primary anatomical source of her varus deformity is the proximal tibia.Options A, C, D, and E are incorrect because the mLDFA is normal, ruling out the distal femur as the primary source, and the other angles (LPFA, mLDTA, JLCA) are not provided or are not the primary indicators for a varus knee deformity originating in the femur or tibia.

Question 235

Topic: Lower Extremity Trauma

A 30-year-old patient requires correction of a severe valgus deformity of the distal femur. The CORA is located within the distal femoral epiphysis, making an osteotomy directly at the CORA impractical due to limited space for fixation. The surgeon plans to perform the osteotomy 5 cm proximal to the CORA, but still place the Angulation Correction Axis (ACA) at the CORA. According to Paley's principles, what is the expected outcome of this approach?

. A pure angular correction with no translation required.
. An unintended secondary translational deformity will inevitably occur.
. A pure angular correction will be achieved, but with obligatory translation at the osteotomy site.
. The mechanical axis will not be fully restored, leading to residual malalignment.
. The bone ends will remain perfectly apposed, maximizing surface area for healing.

Correct Answer & Explanation

. A pure angular correction will be achieved, but with obligatory translation at the osteotomy site.

Explanation

Correct Answer: CThis scenario perfectly describes Paley's Osteotomy Rule 2: Correction with Obligatory Translation. When anatomical constraints (like limited space in the epiphysis) prevent the osteotomy from being performed directly at the CORA, the osteotomy must be moved away from it. However, if the Angulation Correction Axis (ACA) is still placed at the CORA, a pure angular correction of the axis is still possible. The critical consequence is that the farther the osteotomy level is from the CORA, the more intentional translation is required at the osteotomy site to avoid creating secondary deformities and to keep the mechanical axis aligned. The amount of translation is mathematically predictable and essential for periarticular osteotomies.Option A is incorrect because translation is required. Option B is incorrect because if planned correctly (as per Rule 2), the translation is intentional and prevents anunintendedsecondary deformity. Option D is incorrect because the mechanical axiscanbe fully restored with planned translation. Option E is incorrect because translation means the bone ends will not be perfectly apposed, but rather intentionally offset.

Question 236

Topic: Lower Extremity Trauma

A 45-year-old female presents with severe genu varum. Standing long-leg radiographs demonstrate a mechanical axis deviation (MAD) passing 30 mm medial to the knee center. The mechanical lateral distal femoral angle (mLDFA) is 88° and the medial proximal tibial angle (MPTA) is 87°. The joint line congruency angle (JLCA) is 7° (medial opening). What is the primary source of her varus deformity?

. Femoral diaphyseal bowing
. Proximal tibial metaphyseal varus
. Lateral compartment cartilage loss or lateral collateral ligament laxity
. Medial collateral ligament laxity
. Medial compartment cartilage loss or lateral collateral ligament laxity

Correct Answer & Explanation

. Lateral compartment cartilage loss or lateral collateral ligament laxity

Explanation

Normal mLDFA (85-90°) and MPTA (85-90°) exclude osseous deformities of the distal femur and proximal tibia. An abnormally high JLCA (>2°) in a varus knee suggests an intra-articular deformity, such as medial compartment cartilage loss or lateral collateral ligament laxity causing medial joint line opening.

Question 237

Topic: Lower Extremity Trauma

A 50-year-old male with symptomatic knee osteoarthritis has a Mechanical Lateral Distal Femoral Angle (mLDFA) of 95° and a normal Medial Proximal Tibial Angle (MPTA) of 87°. The mechanical axis deviation (MAD) is lateral. What is the correct description of the primary deformity?

. Distal femoral valgus
. Distal femoral varus
. Proximal tibial valgus
. Proximal tibial varus
. Intra-articular varus

Correct Answer & Explanation

. Distal femoral varus

Explanation

Normal mLDFA is 85-90°. An mLDFA > 90° indicates a distal femoral varus deformity. Since the angle is measured on the lateral side, an angle greater than 90° means the distal femur is pointing medially (varus).

Question 238

Topic: Lower Extremity Trauma

A patient with severe varus deformity of the knee presents with a Mechanical Axis Deviation (MAD) of 45 mm medial. The MPTA is 87 degrees, and the mLDFA is 88 degrees. The Joint Line Convergence Angle (JLCA) is measured at 8 degrees (apex lateral). What is the primary source of the varus deformity?

. Femoral shaft bowing
. Proximal tibial structural varus
. Intra-articular joint space narrowing and/or ligamentous laxity
. Distal tibial deformity
. Rotational malalignment of the femur

Correct Answer & Explanation

. Intra-articular joint space narrowing and/or ligamentous laxity

Explanation

The MPTA and mLDFA are within normal limits (average 87 and 88 degrees, respectively), ruling out osseous deformity. A JLCA greater than 2 degrees indicates that the deformity originates within the joint itself, such as from cartilage loss or ligamentous laxity.

Question 239

Topic: Lower Extremity Trauma

A surgeon is evaluating the sagittal plane alignment of a tibia prior to deformity correction. What is the normal average Posterior Proximal Tibial Angle (PPTA), and what does it represent regarding the tibial plateau?

. 90 degrees, representing a perfectly orthogonal plateau.
. 81 degrees, representing approximately 9 degrees of posterior slope.
. 88 degrees, representing approximately 2 degrees of posterior slope.
. 75 degrees, representing approximately 15 degrees of posterior slope.
. 95 degrees, representing 5 degrees of anterior slope.

Correct Answer & Explanation

. 81 degrees, representing approximately 9 degrees of posterior slope.

Explanation

The normal average PPTA is 81 degrees. Since 90 degrees would be perfectly perpendicular to the anatomic axis, an 81-degree PPTA correlates with a normal 9-degree posterior slope of the tibial plateau.

Question 240

Topic: Lower Extremity Trauma

A 45-year-old male presents with a valgus knee deformity. Standing long-leg radiographs demonstrate a mechanical axis deviation (MAD) lateral to the center of the knee. The Mechanical Lateral Distal Femoral Angle (mLDFA) is 81° and the Medial Proximal Tibial Angle (MPTA) is 88°. What is the primary anatomical source of the deformity?

. Proximal tibia
. Distal femur
. Intra-articular joint line convergence
. Combined femoral and tibial deformities
. Ligamentous laxity of the medial collateral ligament

Correct Answer & Explanation

. Distal femur

Explanation

Normal mLDFA is 87°-90° and normal MPTA is 85°-90°. An mLDFA of 81° is abnormally low, indicating a valgus deformity of the distal femur, while the tibia (MPTA) is normal.

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